[Federal Register Volume 68, Number 106 (Tuesday, June 3, 2003)]
[Proposed Rules]
[Pages 33284-33316]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-13254]
[[Page 33283]]
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Part III
Environmental Protection Agency
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40 CFR Part 82
Protection of Stratospheric Ozone: Listing of Substitutes for Ozone-
Depleting Substances--n-Propyl Bromide; Proposed Rule
Federal Register / Vol. 68, No. 106 / Tuesday, June 3, 2003 /
Proposed Rules
[[Page 33284]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 82
[FRL-7504-3]
RIN 2060-AK28
Protection of Stratospheric Ozone: Listing of Substitutes for
Ozone-Depleting Substances--n-Propyl Bromide
AGENCY: Environmental Protection Agency.
ACTION: Notice of proposed rulemaking.
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SUMMARY: This action proposes to list n-propyl bromide (nPB) as an
acceptable substitute for ozone-depleting substances (ODSs), subject to
use conditions, in the solvent cleaning sector and aerosol solvents and
adhesive end uses under the U.S. Environmental Protection Agency's (EPA
or ``we'') Significant New Alternatives Policy (SNAP) program. The SNAP
program implements section 612 of the amended Clean Air Act of 1990
(CAA), which requires EPA to evaluate substitutes for ODSs in order to
reduce overall risk to human health and the environment.
While we find that nPB has a short atmospheric lifetime and low
ozone depletion potential when emitted from locations in the
continental U.S., the Agency cautions that significant use of nPB
closer to the equator poses significant risks to the stratospheric
ozone layer. Further, if workplace exposure to nPB is poorly
controlled, it may increase health risks to workers. In the interim,
until the Occupational Safety and Health Administration (OSHA) develops
a mandatory workplace exposure limit under Section 6 of the
Occupational Safety and Health Act, the Agency recommends that users of
nPB adhere to an acceptable exposure limit of 25 parts per million
(ppm) over an eight-hour time-weighted average.
In today's action, EPA proposes that the use of nPB is acceptable
subject to a use condition, in a limited number of specific
applications where emissions can be tightly controlled for both
environmental and exposure concerns. The proposal only allows the use
of nPB as a solvent in metals, precision, and electronics cleaning, and
in aerosol solvent and adhesive end-uses. EPA is proposing to list nPB
as an acceptable substitute for chlorofluorocarbon (CFC)-113,
hydrochlorofluorocarbon (HCFC)-141b, and methyl chloroform when used in
aerosol solvent and adhesive end uses, subject to the condition that
nPB used in these end uses not contain more than 0.05% isopropyl
bromide by weight before adding stabilizers or other chemicals. We are
also proposing to list nPB as an acceptable substitute for CFC-113 and
methyl chloroform in general metals cleaning, electronics cleaning, and
precision cleaning, subject to the condition that nPB used in these end
uses not contain more than 0.05% isopropyl bromide by weight before
adding stabilizers or other chemicals.
DATES: Comments must be received in writing by August 4, 2003.
ADDRESSES: Comments may be submitted by mail to: Air and Radiation
Docket, Environmental Protection Agency, Mailcode 6102T, 1200
Pennsylvania Ave., NW., Washington, DC 20460, Attention Docket ID No.
OAR-2002-0064. Comments may also be submitted electronically, by
facsimile, or through hand delivery/courier. Follow the detailed
instructions as provided at the beginning of the ``supplementary
information'' section.
FOR FURTHER INFORMATION CONTACT: For further information about this
proposed rule, contact Margaret Sheppard by telephone at (202) 564-
9163, or by e-mail at [email protected]. Notices and
rulemakings under the SNAP program are available on EPA's Stratospheric
Ozone World Wide Web site at http://www.epa.gov/ozone/snap/regs.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. General Information
A. Regulated entities
B. How can I get copies of related information?
C. How and to whom do I submit comments?
D. How should I submit CBI to the agency?
E. Acronyms and abbreviations used in the preamble
II. How does the Significant New Alternatives Policy (SNAP) program
work?
A. What are the statutory requirements and authority for the
SNAP program?
B. How do the regulations for the SNAP program work?
C. Where can I get additional information about the SNAP
program?
III. Is EPA listing n-propyl bromide as an acceptable substitute for
ozone-depleting substances?
A. What is EPA proposing today?
B. What is n-propyl bromide?
C. What industrial sectors are included in our proposed
decision?
IV. What did EPA consider in preparing today's proposal?
A. Toxicity
1. What Acceptable Exposure Limit is EPA recommending for n-
propyl bromide, and why?
a. Summary of toxicity studies
b. Derivation of an AEL for nPB
c. Overview of the Center for Evaluation of Risk to Human
Reproduction (CERHR) Expert Panel Report
d. AELs suggested by other reviewers and outside parties
e. Feasibility of meeting the AEL for nPB in each sector
2. Are there other entities that may set workplace standards for
nPB?
3. Is the general population exposed to too much nPB?
4. What limit is EPA setting on isopropyl bromide contamination
of n-propyl bromide as a condition of acceptability, and why?
B. Ozone depletion potential
C. Global warming potential
D. Flammability
E. Other environmental concerns
F. Comparison of nPB to other solvents
V. What other factors did EPA consider that are unique to nPB?
A. Continued review of nPB by other federal and international
programs
B. Potential market for n-propyl bromide
C. Estimated economic impacts on businesses
VI. How is EPA responding to comments on the advance notice of
proposed rulemaking and December 18, 2000 notice of data
availability?
VII. What should I include in my comments on EPA's proposal?
VIII. What is the federal government doing to help businesses use
nPB safely?
IX. How can I use nPB as safely as possible?
X. Statutory and Executive Order Reviews
XI. References
I. General Information
A. Regulated Entities
Today's proposal would regulate the use of n-propyl bromide as a
solvent used in industrial equipment for metals cleaning, electronics
cleaning, or precision cleaning, and as an aerosol solvent and a
carrier solvent in adhesives. Businesses that currently might be using
nPB, or might want to use it in the future, include:
[sbull] Businesses that clean metal parts, such as automotive
manufacturers, machine shops, machinery manufacturers, and
electroplaters.
[sbull] Businesses that manufacture electronics or computer
equipment.
[sbull] Businesses that require a high level of cleanliness in
removing oil, grease, or wax, such as for aerospace applications or for
manufacture of optical equipment.
[sbull] Foam fabricators that glue pieces of polyurethane foam
together or foam cushion manufacturers that glue fabric around a
cushion.
[sbull] Furniture manufacturers that use adhesive to attach wood
parts to floors, tables and counter tops.
Regulated entities may include:
[[Page 33285]]
Table 1.--Potentially Regulated Entities, by North American Industrial
Classification System (NAICS) Code or Subsector
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NAICS
Category code or Description of regulated
subsector entities
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Industry...................... 331 Primary metal manufacturing
Industry...................... 332 Fabricated metal product
manufacturing
Industry...................... 333 Machinery manufacturing
Industry...................... 334 Computer and electronic
product manufacturing
Industry...................... 336 Transportation equipment
manufacturing
Industry...................... 337 Furniture and related product
manufacturing
Industry...................... 326150 Urethane and other foam
product (except polystyrene)
manufacturing
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This table is not intended to be exhaustive, but rather a guide
regarding entities likely to be regulated by this action. If you have
any questions about whether this action applies to a particular entity,
consult the person listed in the preceding section, FOR FURTHER
INFORMATION CONTACT.
B. How Can I Get Copies of Related Information?
1. Docket
EPA has established an official public docket for this action under
Docket ID No. OAR-2002-0064 (continuation of Docket A-2001-07). The
official public docket consists of the documents specifically
referenced in this action, any public comments received, and other
information related to this action. Hard copies of documents from prior
to the public comment period are found under Docket ID No. A-2001-07.
Although a part of the official docket, the public docket does not
include Confidential Business Information (CBI) or other information
whose disclosure is restricted by statute. The official public docket
is the collection of materials that is available for public viewing at
the Air and Radiation Docket in the EPA Docket Center, (EPA/DC) EPA
West, Room B102, 1301 Constitution Ave., NW., Washington, DC. The EPA
Docket Center Public Reading Room is open from 8:30 a.m. to 4:30 p.m.,
Monday through Friday, excluding legal holidays. The telephone number
for the Reading Room is (202) 566-1742, and the telephone number for
the Air and Radiation Docket is (202) 566-1742.
2. Electronic Access
An electronic version of the public docket is available through
EPA's electronic public docket and comment system, EPA Dockets. You may
use EPA Dockets at http://www.epa.gov/edocket/ to submit or view public
comments, access the index listing of the contents of the official
public docket, and to access those documents in the public docket that
are available electronically. Once in the system, select ``search,''
then key in the appropriate docket identification number.
Certain types of information will not be placed in the EPA
Dockets.Information claimed as CBI and other information whose
disclosure is restricted by statute, which is not included in the
official public docket, will not be available for public viewing in
EPA's electronic public docket. EPA's policy is that copyrighted
material will not be placed in EPA's electronic public docket but will
be available only in printed, paper form in the official public docket.
Although not all docket materials may be available electronically, you
may still access any of the publicly available docket materials through
the docket facility identified in section I.B.1. above.
For public commenters, it is important to note that EPA's policy is
that public comments, whether submitted electronically or in paper,
will be made available for public viewing in EPA's electronic public
docket as EPA receives them and without change, unless the comment
contains copyrighted material, CBI, or other information whose
disclosure is restricted by statute. When EPA identifies a comment
containing copyrighted material, EPA will provide a reference to that
material in the version of the comment that is placed in EPA's
electronic public docket. The entire printed comment, including the
copyrighted material, will be available in the public docket.
Public comments submitted on computer disks that are mailed or
delivered to the docket will be transferred to EPA's electronic public
docket. Public comments that are mailed or delivered to the Docket will
be scanned and placed in EPA's electronic public docket. Where
practical, physical objects will be photographed, and the photograph
will be placed in EPA's electronic public docket along with a brief
description written by the docket staff.
C. How and to Whom Do I Submit Comments?
You may submit comments electronically, by mail, by facsimile, or
through hand delivery/courier. To ensure proper receipt by EPA,
identify the appropriate docket identification number in the subject
line on the first page of your comment. Please ensure that your
comments are submitted within the specified comment period. Comments
received after the close of the comment period will be marked ``late.''
EPA is not required to consider these late comments. If you wish to
submit CBI or information that is otherwise protected by statute,
please follow the instructions in section I.D. Do not use EPA Dockets
or e-mail to submit CBI or information protected by statute.
1. Electronically. If you submit an electronic comment as
prescribed below, EPA recommends that you include your name, mailing
address, and an e-mail address or other contact information in the body
of your comment. Also include this contact information on the outside
of any disk or CD ROM you submit, and in any cover letter accompanying
the disk or CD ROM. This ensures that you can be identified as the
submitter of the comment and allows EPA to contact you in case EPA
cannot read your comment due to technical difficulties or needs further
information on the substance of your comment. EPA's policy is that EPA
will not edit your comment, and any identifying or contact information
provided in the body of a comment will be included as part of the
comment that is placed in the official public docket, and made
available in EPA's electronic public docket. If EPA cannot read your
comment due to technical difficulties and cannot contact you for
clarification, EPA may not be able to consider your comment.
Your use of EPA's electronic public docket to submit comments to
EPA electronically is EPA's preferred method for receiving comments. Go
directly to EPA Dockets at http://www.epa.gov/edocket, and follow the
online instructions for submitting comments. To access EPA's electronic
public docket from the EPA Internet Home Page, select ``Information
Sources,'' ``Dockets,'' and ``EPA Dockets.'' Once in the system, select
``search,'' and then key in Docket ID No. OAR-2002-0064. The system is
an ``anonymous access'' system, which means EPA will not know your
identity, e-mail address, or other contact information unless you
provide it in the body of your comment.
Comments may be sent by electronic mail (e-mail) to A-And-R-
[[Page 33286]]
[email protected], Attention Docket ID No. OAR-2002-0064. In contrast to
EPA's electronic public docket, EPA's e-mail system is not an
``anonymous access'' system. If you send an e-mail comment directly to
the Docket without going through EPA's electronic public docket, EPA's
e-mail system automatically captures your e-mail address. E-mail
addresses that are automatically captured by EPA's e-mail system are
included as part of the comment that is placed in the official public
docket, and made available in EPA's electronic public docket.
You may submit comments on a disk or CD ROM that you mail to the
mailing address identified in section I.B.1. These electronic
submissions will be accepted in WordPerfect or ASCII file format. Avoid
the use of special characters and any form of encryption.
2. By Mail. Send two copies of your comments to: Air and Radiation
Docket, Environmental Protection Agency, Mailcode: 6102T, 1200
Pennsylvania Ave., NW., Washington DC, 20460, Attention: Docket ID No.
OAR-2002-0064.
3. By Hand Delivery or Courier. Deliver your comments to: EPA
Docket Center, (EPA/DC) EPA West, Room B102, 1301 Constitution Ave.,
NW., Washington, DC, Attention Docket ID No. OAR-2002-0064. Such
deliveries are only accepted during the Docket's normal hours of
operation as identified in section I.B.1.
4. By Facsimile. Fax your comments to: 202-566-1741, Attention:
Docket ID No. OAR-2002-0064.
D. How Should I Submit CBI to the Agency?
Do not submit information that you consider to be CBI
electronically through EPA's electronic public docket or by e-mail.
Send or deliver information identified as CBI only to the following
address: Margaret Sheppard, U.S. EPA, 4th floor, 501 3rd Street NW.,
Washington DC 20001, via delivery service. You may claim information
that you submit to EPA as CBI by marking any part or all of that
information as CBI (if you submit CBI on disk or CD ROM, mark the
outside of the disk or CD ROM as CBI and then identify electronically
within the disk or CD ROM the specific information that is CBI).
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR part 2.
In addition to one complete version of the comment that includes
any information claimed as CBI, a copy of the comment that does not
contain the information claimed as CBI must be submitted for inclusion
in the public docket and EPA's electronic public docket. If you submit
the copy that does not contain CBI on disk or CD ROM, mark the outside
of the disk or CD ROM clearly that it does not contain CBI. Information
not marked as CBI will be included in the public docket and EPA's
electronic public docket without prior notice. If you have any
questions about CBI or the procedures for claiming CBI, please consult
the person identified in the FOR FURTHER INFORMATION CONTACT section.
E. Acronyms and Abbreviations Used in the Preamble
Below is a list of acronyms and abbreviations used in this
document.
1,1,1--the ozone-depleting chemical 1,1,1-trichloroethane, CAS Reg.
No. 71-55-6; also called TCA, methyl chloroform, or MCF
1-BP--the chemical 1-bromopropane, C3H7Br,
CAS Reg. No. 106-94-5; also called n-propyl bromide or nPB
2-BP--the chemical 2-bromopropane, C3H7Br,
CAS Reg. No. 75-26-3; also called isopropyl bromide or iPB
2-D--two-dimensional
3-D--three dimensional
ACGIH--American Congress of Governmental Industrial Hygienists
AEL--acceptable exposure limit
AFEAS--Alternative Flurocarbon Environmental Acceptability Study
AIC--Akaike Information Criterion
AIHA--American Industrial Hygienists Association
ANPRM--Advance Notice of Proposed Rulemaking
ASTM--American Society for Testing and Materials
BMD--benchmark dose
BMDL--benchmark dose lowerbound, the lower 95%-confidence level
bound on the dose/exposure associated with the benchmark response
BMR--benchmark response
BSOC--Brominated Solvents Consortium
CAA--Clean Air Act
CAS Reg. No.--Chemical Abstracts Service Registry Identification
Number
CBI--Confidential Business Information
CERHR--Center for the Evaluation of Risks to Human Reproduction
CFC-113--the ozone-depleting chemical trifluorotrichloroethane,
C2Cl3F3, CAS Reg. No. 76-13-1
CFCs--chlorofluorocarbons
CFR--Code of Federal Regulations
CNS--Central nervous system
EPA--the United States Environmental Protection Agency
FR--Federal Register
GLP--Good Laboratory Practice
GWP--global warming potential
HCFC-123--the ozone-depleting chemical 1,2-dichloro-1,1,2-
trifluoroethane, CAS Reg. No. 306-83-2
HCFC-141b--the ozone-depleting chemical 1,1,1-trichloro-2-
fluoroethane, CAS Reg. No. 1717-00-6
HCFC-225ca/cb--the commercial mixture of the two ozone-depleting
chemicals 3,3-dichloro-1,1,1,2,2-pentafluoro-propane, CAS Reg. No. 422-
56-0 and 3,3-dichloro-1,1,2,2,3-pentafluoropropane, CAS Reg. No. 507-
55-1
HCFCs--hydrochlorofluorocarbons
HEC--human equivalent concentration
HESIS--Hazard Evaluation System and Information Service of the
California Department of Health Services
HFC-245fa--the chemical 1,1,3,3,3-pentafluoropropane, CAS Reg. No.
460-73-1
HFC-365mfc--the chemical 1,1,3,3,3-pentafluorobutane, CAS Reg. No.
405-58-6
HFC-4310mee--the chemical 1,1,1,2,3,4,4,5,5,5-decafluoropentane,
CAS Reg. No. 138495-42-8
HFCs--hydrofluorocarbons
HFEs--hydrofluoroethers
HHE--health hazard evaluation
HSIA--Halogenated Solvents Industry Alliance
IARC--International Agency for Research on Cancer
ICF--ICF Consulting
ICR--Information Collection Request
iPB--isopropyl bromide, C3H7Br, CAS Reg. No.
75-26-3, an isomer of n-propyl bromide; also called 2-bromopropane or
2-BP
IPCC--International Panel on Climate Change
IRTA--Institute for Research and Technical Assistance
LOAEL--Lowest Observed Adverse Effect Level
MF--modifying factor
MSDS--Material Safety Data Sheet
NAICS--North American Industrial Classification System
NESHAP--National Emission Standards for Hazardous Air Pollutants
NIEHS--National Institute of Environmental Health Services
NIOSH--National Institute for Occupational Safety and Health
NOAEL--No Observed Adverse Effect Level
NOEL--No Observed Effect Level
nPB--n-propyl bromide, C3H7Br, CAS Reg. No.
106-94-5; also called 1-bromopropane or 1-BP
NPRM--Notice of Proposed Rulemaking
NTP--National Toxicology Program
NTTAA--National Technology Transfer and Advancement Act
ODP--ozone depletion potential
ODS--ozone-depleting substance
OMB--U.S. Office of Management and Budget
[[Page 33287]]
OSHA--U.S. Occupational Safety and Health Administration
PCBTF--parachlorobenzotrifluoride, CAS Reg. No. 98-56-6
PEL--Permissible Exposure Limit
PERC--perchloroethylene, also called tetrachloroethylene;
C2Cl4, CAS Reg. No. 127-18-4
POD--point of departure
ppm--parts per million
RCRA--Resource Conservation and Recovery Act
RFA--Regulatory Flexibility Act
RfC--reference concentration
RfD--reference dose
SBREFA--Small Business Regulatory Enforcement Fairness Act
SNAP--Significant New Alternatives Policy
STEL--short term exposure limit
TCA--the ozone-depleting chemical 1,1,1-trichloroethane, CAS Reg.
No. 71-55-6; also called 1,1,1, methyl chloroform, or MCF
TCE--trichloroethylene, C2Cl3H, CAS Reg. No.
79-01-6
TEAP--Technical and Economic Assessment Panel of the United Nations
Environmental Programme
TSCA--Toxic Substances Control Act
TWA--time-weighted average
UF--uncertainty factor
UMRA--Unfunded Mandates Reform Act
UNEP--United Nations Environmental Programme
VMSs--volatile methyl siloxanes
VOC--volatile organic compound
II. How Does the Significant New Alternatives Policy (SNAP) Program
Work?
A. What Are the Statutory Requirements and Authority for the SNAP
Program?
Section 612 of the Clean Air Act (CAA) authorizes EPA to develop a
program for evaluating alternatives to ozone-depleting substances,
referred to as the Significant New Alternatives Policy (SNAP) program.
The major provisions of section 612 are:
[sbull] Rulemaking--Section 612(c) requires EPA to promulgate rules
making it unlawful to replace any class I (chlorofluorocarbon, halon,
carbon tetrachloride, methyl chloroform, and hydrobromofluorocarbon) or
class II (hydrochlorofluorocarbon) substance with any substitute that
the Administrator determines may present adverse effects to human
health or the environment where the Administrator has identified an
alternative that (1) reduces the overall risk to human health and the
environment, and (2) is currently or potentially available.
[sbull] Listing of Unacceptable/Acceptable Substitutes--Section
612(c) also requires EPA to publish a list of the substitutes
unacceptable for specific uses. We must publish a corresponding list of
acceptable alternatives for specific uses.
[sbull] Petition Process--Section 612(d) grants the right to any
person to petition EPA to add a substitute to or delete a substitute
from the lists published in accordance with section 612(c). EPA has 90
days to grant or deny a petition. Where the Agency grants the petition,
we must publish the revised lists within an additional six months.
[sbull] 90-day Notification--Section 612(e) requires EPA to require
any person who produces a chemical substitute for a class I substance
to notify the Agency not less than 90 days before new or existing
chemicals are introduced into interstate commerce for significant new
uses as substitutes for a class I substance. The producer must also
provide the Agency with the producer's health and safety studies on
such substitutes.
[sbull] Outreach--Section 612(b)(1) states that the Administrator
shall seek to maximize the use of federal research facilities and
resources to assist users of class I and II substances in identifying
and developing alternatives to the use of such substances in key
commercial applications.
[sbull] Clearinghouse--Section 612(b)(4) requires the Agency to set
up a public clearinghouse of alternative chemicals, product
substitutes, and alternative manufacturing processes that are available
for products and manufacturing processes which use class I and II
substances.
B. How Do the Regulations for the SNAP Program Work?
On March 18, 1994, EPA published the original rulemaking (59 FR
13044) that described the process for administering the SNAP program
and issued our first acceptability lists for substitutes in the major
industrial use sectors. These sectors include: Refrigeration and air
conditioning; foam blowing; solvents cleaning; fire suppression and
explosion protection; sterilants; aerosols; adhesives, coatings and
inks; and tobacco expansion. These sectors comprise the principal
industrial sectors that historically consumed large volumes of ozone-
depleting substances.
Anyone who produces a substitute for an ODS must provide the Agency
with health and safety studies on the substitute at least 90 days
before introducing it into interstate commerce for significant new use
as an alternative. This requirement applies to chemical manufacturers,
but may include importers, formulators or end-users when they are
responsible for introducing a substitute into commerce.
The Agency has identified four possible decision categories for
substitutes: acceptable; acceptable subject to use conditions;
acceptable subject to narrowed use limits; and unacceptable.
Use conditions and narrowed use limits are both considered ``use
restrictions'' and are explained below. Substitutes that are deemed
acceptable with no use restrictions (no use conditions or narrowed use
limits) can be used for all applications within the relevant sector
end-use. Substitutes that are acceptable subject to use restrictions
may be used only in accordance with those restrictions. It is illegal
to replace an ODS with a substitute listed as unacceptable.
After reviewing a substitute, the Agency may make a determination
that a substitute is acceptable only if certain conditions of use are
met to minimize risks to human health and the environment. We describe
such substitutes as ``acceptable subject to use conditions.'' If you
use these substitutes without meeting the associated use conditions,
you use these substitutes in an unacceptable manner and you could be
subject to enforcement for violation of section 612 of the Clean Air
Act.
For some substitutes, the Agency may permit a narrowed range of use
within a sector (that is, we may limit the use of a substitute to
certain end-uses or specific applications within an industry sector),
to allow alternatives to be used in specific uses that would otherwise
be deemed unacceptable. We describe these substitutes as ``acceptable
subject to narrowed use limits.'' If you use a substitute that is
acceptable subject to narrowed use limits, but use it in applications
and end-uses which are not specified as acceptable in the narrowed use
limit, you are using these substitutes in an unacceptable manner and
you could be subject to enforcement for violation of section 612 of the
Clean Air Act.
The Agency publishes its SNAP program decisions in the Federal
Register. For those substitutes that are deemed acceptable subject to
use restrictions (use conditions and/or narrowed use limits), or for
substitutes deemed unacceptable, we first publish these decisions as
proposals to allow the public opportunity to comment, and we publish
final decisions as final rulemakings.
In contrast, we publish substitutes that are deemed acceptable with
no restrictions in ``notices of acceptability,'' rather than as
proposed and final rules. As described in the rule implementing
[[Page 33288]]
the SNAP program (59 FR 13044), we do not believe that rulemaking
procedures are necessary to list alternatives that are acceptable
without restrictions because such listings neither impose any sanction
nor prevent anyone from using a substitute.
Many SNAP listings include ``comments'' or ``further information.''
These statements provide additional information on substitutes that we
determine are either unacceptable, acceptable subject to narrowed use
limits, or acceptable subject to use conditions. Since this additional
information is not part of the regulatory decision, you are not
required to follow these statements to use a substitute unless they
specifically reference regulatory requirements. The further information
does not necessarily include all other legal obligations pertaining to
the use of the substitute. However, we encourage users of substitutes
to apply all statements in the ``Further Information'' column in their
application of these substitutes, regardless of any regulatory
requirements. In many instances, the information simply refers to sound
operating practices that have already been identified in existing
industry and/or building-code standards. Thus, many of the comments, if
adopted, would not require the affected industry to make significant
changes in existing operating practices.
C. Where Can I Get Additional Information About the SNAP Program?
For copies of the comprehensive SNAP lists of substitutes or
additional information on SNAP, look at EPA's Ozone Depletion World
Wide Web site at http://www.epa.gov/ozone/snap/lists/index.html. For
more information on the Agency's process for administering the SNAP
program or criteria for evaluation of substitutes, refer to the SNAP
final rulemaking published in the Federal Register on March 18, 1994
(59 FR 13044), codified at Code of Federal Regulations at 40 CFR part
82, subpart G. You can find a complete chronology of SNAP decisions and
the appropriate Federal Register citations at http://www.epa.gov/ozone/snap/chron.html.
III. Is EPA Listing n-Propyl Bromide as an Acceptable Substitute for
Ozone-Depleting Substances?
A. What Is EPA Proposing Today?
EPA is proposing today to list n-propyl bromide (nPB) acceptable,
subject to use conditions, for use as a substitute for CFC-113 and
methyl chloroform \1\ in metals, precision and electronics cleaning,
and acceptable, subject to use conditions, for use as a substitute for
CFC-113, methyl chloroform and HCFC-141b in adhesives and aerosol
solvent end uses. The use conditions for each end use provide that nPB
not contain more than 0.05% isopropyl bromide (iPB)\2\ by weight before
adding stabilizers or other chemicals. By this, we mean the chemical n-
propyl bromide that is produced by the manufacturer or reclaimed by a
recycler before other substances are added, such as stabilizers, other
solvents, or adhesive solids. End users would need to keep
documentation for two years from the date on the documentation to show
that the nPB-based product that they are using contains no more than
0.05% iPB in the nPB. EPA's decision is based upon comparing
environmental and health risks associated with the use of nPB in
specific applications in the United States, compared to other available
alternatives. Based on our review, the impact of using nPB in the U.S.
does not warrant listing the chemical as an unacceptable substitute
under the SNAP program.
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\1\ Methyl chloroform is also referred to as 1,1,1-
trichloroethane, TCA, or 1,1,1.
\2\ iPB is also referred to as 2-bromopropane, 2-propyl bromide,
or 2-BP. Its CAS registration number is 75-26-3.
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We recommend, but do not require, that users in all industrial
sectors adhere to EPA's recommended guideline for worker exposure of 25
parts per million (ppm) over an eight-hour time-weighted average. While
we believe it is possible to achieve the recommended exposure limit of
25 ppm in the kinds of applications listed above, we are concerned
about potentially high emissions and exposure levels of nPB in adhesive
applications in particular. Consequently, EPA intends to work with the
National Institute for Occupational Safety and Health (NIOSH) to
develop information for employers and workers at facilities that use,
or could use, nPB. NIOSH and state occupational safety and health
agencies will provide technical assistance to help ensure a safe
workplace environment if owners or workers request it.
EPA strongly recommends that users follow responsible use practices
suggested by the manufacturer when using nPB. You can also reduce risk
in the workplace by monitoring workers' levels of exposure to nPB.
These practices will reduce the risk of toxic effects to workers, as
well as reducing the impact of emissions on the environment.
B. What Is n-Propyl Bromide?
n-propyl bromide (nPB), also called 1-bromopropane, is a non-
flammable organic solvent with a strong odor. Its chemical formula is
C3H7Br. Its identification number in Chemical
Abstracts Service's registry (CAS Reg. No.) is 106-94-5. nPB is used to
remove wax, oil, and grease from electronics, metal, and other
materials. It also is used as a carrier solvent in adhesives. Some
brand names of products using nPB are: Abzol[reg], EnSolv[reg], and
Solvon[reg] cleaners, and Whisper Spray and Fire Retardant Soft Seam
6460 adhesives.
C. What Industrial Sectors Are Included in Our Proposed Decision?
EPA has received petitions under CAA Section 612(d) to add nPB to
the list of acceptable alternatives for CFC-113, methyl chloroform, and
HCFC-141b in the solvent cleaning sector for general metals, precision,
and electronics cleaning, as well as in aerosol solvent and adhesive
applications.\3\ Today's proposal does not list nPB as a substitute for
HCFC-141b for the solvent cleaning sector, but does list nPB as an
acceptable substitute for HCFC-141b, subject to use conditions, for
aerosol solvents. This is because EPA previously listed HCFC-141b as
unacceptable for use in non-aerosol solvent cleaning applications
because of the availability of safer alternatives (59 FR 13090; March
18, 1994), and listed HCFC-141b as acceptable for use in aerosol
solvents. No one may legally use HCFC-141b for non-aerosol solvent
cleaning and, therefore, no one would substitute for its use.
---------------------------------------------------------------------------
\3\ EPA also received petitions for using nPB in the foam
blowing and fire suppression sectors. Because the information in
these petitions about the use of nPB is incomplete, EPA was unable
to consider them. Therefore, today's action does not address nPB's
use in the foam blowing and fire suppression sectors.
---------------------------------------------------------------------------
The proposal for aerosol solvents only applies to a limited number
of aerosol solvent applications because of the Nonessential Products
Ban promulgated under Section 610 of the Act which prohibits the sale,
distribution, or offer for sale or distribution in interstate commence
of many products containing CFCs and HCFCs. All aerosol products,
pressurized dispensers and foam products containing or manufactured
with CFCs and HCFCs--except those specifically exempted by the
regulations at 40 CFR part 82, subpart C, and those that are listed as
essential medical devices by the Food and Drug Administration at 21 CFR
2.125(e)--are banned from sale and distribution in the
[[Page 33289]]
United States. Users of aerosol solvents can purchase them only for
those applications that are exempted from the Non-Essential Products
Ban. The SNAP program applies to the use of substitutes for ODSs, and
thus, applies only to those applications where ODSs may be used.
Therefore, today's proposed listing only applies to those specific
aerosol solvent applications where ODSs are allowed to be sold. This
list of permissible uses is subject to change. Of the allowable
applications for aerosol solvents, it is most likely that nPB would be
used as a solvent in:
[sbull] Lubricants, coatings, or cleaning fluids for electrical or
electronic equipment;
[sbull] Lubricants, coatings, or cleaning fluids for aircraft
maintenance; or
[sbull] Spinnerrette lubricants and cleaning sprays used in the
production of synthetic fibers.
In addition, no one has specifically stated that they use, or
intend to use, nPB in coatings or inks. Thus, our proposed ruling only
addresses nPB use in the adhesives end use, in the adhesives, coatings,
and inks sector. We would require a separate SNAP submission and
additional information on nPB use and exposure data in coatings and
inks to consider its acceptability in those applications.
EPA notes that the SNAP program currently does not cover some uses
of solvents, such as manual cleaning, carriers for flame retardants,
dry cleaning, or paint stripping. Ozone-depleting solvents were never
used in significant quantities in these applications, compared to
applications that are covered by the SNAP program, such as vapor
degreasing or cold batch cleaning. For further discussion, see the
original SNAP rule (March 18, 1994; 59 FR 13089-13090 and 59 FR 13117-
13120).
We summarize our proposed actions by sector and end use in Table 2
below.
Table 2.--Summary of Proposed Actions by Sector and End Use
----------------------------------------------------------------------------------------------------------------
as a substitute for these ozone
depleting substances:
For this industrial sector... in this end we propose to list -----------------------------------------
use... nPB as follows... methyl
CFC-113 chloroform HCFC-141b
----------------------------------------------------------------------------------------------------------------
Solvents Cleaning............ Metals Cleaning. Acceptable, subject X X ............
to use conditions\1\.
Electronics Acceptable, subject X X ............
Cleaning. to use conditions\1\.
Precision Acceptable, subject X X ............
Cleaning. to use conditions\1\.
------------------------------
Aerosols..................... Aerosol Solvents Acceptable, subject X X X
to use conditions\1\.
------------------------------
Adhesives, Coatings, and Inks Adhesives....... Acceptable, subject X X X
to use conditions\1\.
----------------------------------------------------------------------------------------------------------------
\1\ In order to use nPB, the nPB would have to contain no more than 0.05% iPB by weight before adding
stabilizers or other chemicals.
At the end of today's action, you will find language that we are
proposing to add as Appendix L to subpart G of 40 CFR part 82 to
summarize our proposed listing decisions. Information contained in the
``Further Information'' column of those tables provides additional
information on nPB. Although EPA expects nPB users to conform to all
information shown in Appendix L, the ``further information'' is not
part of the regulatory decision, and, therefore, is not mandatory.
Also, there may be other legal obligations pertaining to the
manufacture, use, handling, disposal of nPB that are not included in
the comments listed in Appendix L.
IV. What Did EPA Consider for Today's Acceptability Decision?
To assess the acceptability of any substitute, including nPB, EPA
reviews the environmental and health risks potentially posed by the
substitute, including ozone depletion potential, global warming
potential, flammability, and toxicity. Today's action on nPB follows
the publication of an Advanced Notice of Proposed Rulemaking (ANPRM)
published in the Federal Register on February 18, 1999, at 64 FR 8043.
The ANPRM provided the public an opportunity to review the information
available to the Agency at that time, and requested additional
information and comment to assist in the development of regulatory
options. In particular, the ANPRM asked for information on those key
parameters where information was limited--that is, the toxicity, ozone
depletion potential, and market potential of nPB. The Agency also
issued a notice on December 18, 2000 which provided the public with an
update on the information EPA had received regarding nPB's ODP and
toxicity, and provided a summary of anticipated next steps in
developing regulations under SNAP for nPB (65 FR 78977).
Based on all information now available, EPA is proposing to find
nPB acceptable subject to use conditions. The Agency is concerned that
excessive exposure to nPB can pose risks of adverse health effects and
is recommending a workplace exposure guideline that we believe will
protect workers who are exposed to this chemical. EPA is basing this
recommendation on several factors, including a review of the
toxicological literature and a subsequent risk evaluation conducted
according to EPA guidelines (adjusted to represent workplace exposure),
and consideration of risk management principles. EPA finds that it is
possible to reduce workplace exposure to nPB to acceptable levels with
commonly available control equipment or ventilation equipment. Thus,
the Agency has concluded that it is appropriate to list nPB as
acceptable because there is evidence that it can be used in a way that
does not present greater risk than other substitutes.
Based on these data, the Agency is proposing to list nPB as
acceptable, subject to a use condition, for the non-aerosol solvents
cleaning sector, aerosol solvents end use, and adhesives end use
because we believe it is feasible to meet the recommended AEL of 25 ppm
in the solvents cleaning sector, the aerosol solvents end use, and the
adhesives end use. However, EPA expects users to defer to any
permissible exposure limit ultimately established by OSHA. We note that
section 6 of the Occupational Safety and Health Act requires OSHA to
make specific legal findings to support a standard. Specifically, under
the case law OSHA can set a standard only where there is ``substantial
evidence'' that the particular standard will provide
[[Page 33290]]
``significant'' risk reduction of a ``material'' adverse health effect
to workers. Because OSHA operates under a different statute, employs
different methodology, and will presumably have additional data at some
point in the future, OSHA's derivation of a permissible exposure limit
(PEL) may result in a different number than the AEL we set using EPA's
own methodology and the data available today.
Today's proposed decision to find nPB acceptable under the SNAP
program is based in part on its relatively low ozone depletion
potential when emitted within the continental United States. However,
the ODP of nPB varies with latitude; therefore, this decision should
not guide decisions of other countries. For example, nPB emitted closer
to the equator has a significantly higher ozone depleting potential
than nPB emitted from the middle and northern latitudes, which include
the continental United States (for a further discussion, see section
IV.B. below on Ozone Depletion Potential). EPA recommends that any
decisions on the use of nPB outside the U.S. should be based on
latitude-specific ODPs and volumes of the chemical projected to be used
in those regions.
A. Toxicity
A primary concern regarding nPB use in the United States is its
potential adverse health effects to exposed workers. Since EPA
recommended a preliminary exposure guideline in 1999, additional
studies have been conducted on the toxicity of nPB and its isomer, iPB.
EPA has reviewed available toxicity data in order to develop a
contamination limit for iPB and an Acceptable Exposure Limit (AEL)\4\
for occupational exposure to nPB that are protective of human health.
EPA has also reviewed workplace exposure measurements from several
facilities where nPB has been used.
---------------------------------------------------------------------------
\4\ An AEL is the SNAP program's generic term for an eight-hour
time-weighted average occupational exposure limit.
---------------------------------------------------------------------------
1. What Acceptable Exposure Limit Is EPA Recommending for n-Propyl
Bromide, and Why?
Today, EPA is recommending an AEL for nPB of 25 ppm as an eight-
hour time-weighted average. Based upon currently available data, EPA
believes that workers can be exposed to an average nPB concentration of
25 ppm without appreciable risk of adverse health effects. In addition,
like many halogenated solvents, nPB has the potential to be absorbed
through the skin, so we recommend avoiding skin exposure to nPB by
wearing protective clothing and flexible laminated gloves. The
discussion below describes the derivation of the recommended AEL of 25
ppm for workplace exposure.
a. Summary of toxicity studies. EPA reviewed all the studies listed
in docket numbers A-2001-07 and A-91-42 and the studies cited as
references in Section XI at the end of this preamble. The
epidemiological data on nPB are limited. An anecdotal report by Sclar
described neurotoxic effects seen in one patient who used an nPB-based
solvent (Sclar, 1999). Another recently published paper describes three
women exhibiting signs of peripheral and central nervous system
toxicity, such as stumbling, numbness, urinary incontinence, diarrhea,
nausea, difficulty in concentrating, dizziness, and headaches which was
attributed to nPB exposure (Ichihara, 2002a). Because detailed exposure
data are not available in either of these papers, it is difficult to
use this information in a risk assessment. Vibration sense deficits,
decreased nerve conduction, and reduced scores on neurological
functional tests were reported in female workers in China exposed to
nPB between <1 ppm and 49 ppm (Ichihara et al., 2002b). The study
authors concluded that their findings suggest that exposure to nPB at
levels below or around 50 ppm may affect peripheral and central nervous
system function. However, because only an abstract of the study was
available to EPA, it was not possible to determine if the exposures and
effects were well-characterized or if the sample was large enough to
draw reliable conclusions. As discussed below in section IV.A.1.e,
``Feasibility of meeting the AEL for nPB in each industrial sector,''
NIOSH has performed a number of health hazard evaluations with measured
workplace exposures to nPB. However, only one of these studies
attempted to assess health effects (NIOSH, 2002). In this study, NIOSH
conducted a voluntary medical survey and performed a complete blood
count on those workers who chose to participate (43 out of 70 workers
participated). The medical survey included questions on whether workers
had headaches at least once per week, and whether workers had
difficulty having children. No exposure-response relationship could be
identified from these data. The survey was not designed to fully
characterize effects on the reproductive system, nor did the study
employ a control group (a group of workers who were not exposed to
nPB), further limiting the utility of this data for risk assessment.
The acute toxicity of nPB has been studied in Sprague-Dawley rats
for inhalation (Elf Atochem, 1997), oral (Elf Atochem, 1993), and
dermal (Elf Atochem, 1995b) routes of exposure. The 4-hour LC50 (lethal
concentration for 50% of the test animals) for inhalation of nPB was
35,000 mg/m3 (Elf Atochem, 1997), with death resulting from pulmonary
edema. The LD50 (lethal dose for 50% of the test animals) for gavage
dosing of nPB was greater than 2,000 mg/kg (Elf Atochem, 1993).
Animals receiving 2,000 mg/kg nPB dermally (with occlusion of the
exposure area) showed no cutaneous reactions and no evidence of
toxicity (Elf Atochem, 1995b). A skin sensitization test in Guinea pigs
was also negative (Elf Atochem, 1995c).
Key chronic and subchronic toxicological studies on nPB include a
28-day inhalation study (ClinTrials, 1997a), a 90-day inhalation study
(ClinTrials, 1997b), a two-generation reproductive toxicity study (WIL,
2001), and various papers and abstracts published in peer-reviewed
scientific journals (Ichihara, 1998, 1999, 2000a, 2000b; Kim, 1999;
Wang, 1999; Yu, 2001; Ichihara 2002a, 2002b). The results of these
studies consistently show that sensitive health endpoints \5\ (i.e.,
the biological effects occurring at the lowest levels of nPB exposure)
include effects on the liver (centrilobular vacuolation--cellular
changes in the central area of the liver) and on the male reproductive
system (decreases in absolute and relative seminal vesicle weights, and
reduced sperm count, motility and maturation, and effects on sperm
shape).
---------------------------------------------------------------------------
\5\ An endpoint is an observable or measurable biological event
or chemical concentration (e.g., metabolite concentration in a
target tissue) used as an index of an effect of a chemical exposure.
---------------------------------------------------------------------------
The ClinTrials 90-day inhalation study showed liver effects at
exposures of 400 ppm and above, which is consistent with the effects
seen by Kim et al. (1999). Effects of nPB on the central and peripheral
nervous system have also been reported, including peripheral nerve
degeneration and axonal swelling in the spinal cord at 1000 ppm (Yu,
2001), degeneration of the myelin of peripheral nerves at 800 ppm
(Ichihara, 1999), and significantly decreased hind limb grip strength
(a measure of motor nerve function) at 400 ppm (Ichihara, 2000b).
Concerns over potential reproductive toxicity associated with nPB
were initially raised because exposure to iPB,
[[Page 33291]]
a structural analog of nPB, was associated with significant
reproductive effects in both male and female workers (Kim, 1996; Park,
1997; Ichihara, 1997). In animal studies, iPB has been shown to induce
estrous cycle alterations, decreases in accessory sex gland weights
(e.g, seminal vesicle, prostate), reductions in sperm counts and sperm
motility, and changes in sperm morphology (Yu, 1997; Ichihara, 1997;
Kamijima, 1997). Results presented by Ichihara and colleagues indicated
that nPB exerts some level of reproductive toxicity in rats (Ichihara
et al., 1998, 1999; Wang, 1999).
More recently, two studies have reported effects of nPB on the
female reproductive system in rats. In the first study, female rats
were dosed at 0, 200, 400, and 800 ppm for eight hours a day for 7
weeks. Tests of vaginal smears showed a significant increase in the
number of irregular estrous cycles with extended diestrus \6\ in the
400 and 800 ppm dose groups, and dose dependent reduction of the number
of normal antral follicles in the 400 ppm group (Yamada, 2003). In the
second study, female rats were exposed to 1000 ppm nPB for 7 days per
week for three weeks. The ratio of the number of estrous cycles of 6
days or longer to the total number of estrous cycles was calculated for
the 1000 ppm exposure group and the control group. This ratio was two
times higher in the exposed animals than controls, however, this
difference was not statistically significant (Sekiguchi, 2002).
---------------------------------------------------------------------------
\6\ Diestrus is a period of sexual inactivity during the estrous
cycle.
---------------------------------------------------------------------------
In 1999, the Brominated Solvents Consortium (BSOC), a group of
several nPB manufacturers, initiated a two-generation study (WIL, 2001)
designed to investigate thoroughly the reproductive toxicity of nPB, as
well as to provide additional information on other toxic endpoints of
concern, including liver effects, and effects on the central nervous
system (CNS). In this study, groups of 25 male and female rats were
exposed to nPB via whole-body inhalation. The F0, or first generation,
animals were exposed to target air concentrations of 0, 100, 250, 500,
or 750 parts per million (ppm) of nPB for 6 hours/day, 7 days/week for
at least 70 days prior to mating. The F1, or second generation, animals
were exposed to 0, 100, 250, or 500 ppm nPB (infertility in the F0 750
ppm group precluded having an F1 750 ppm group). Exposure of male
animals in both generations continued throughout mating to the day
prior to study termination. Exposure for female animals in both
generations continued throughout mating and gestation through gestation
day 20. After birth of the pups, the females' exposure continued on
lactation day 5 through the day prior to study termination.
In this study, fertility was compromised significantly at 500 ppm,
and no live offspring were produced at 750 ppm. There was strong
evidence of dose-response in both the parent (F0) and offspring (F1)
generations for a constellation of reproductive effects in both males
and females, including decreases in sperm motility and changes in sperm
morphology, reduced numbers of implantation sites and changes in
estrous cycles, and reduced litter size. There were slight decreases
(only some of which were statistically significant) at 250 ppm, and
even 100 ppm for some reproductive endpoints. Statistically significant
effects were observed at 250 ppm for reduced prostate weight in F0
males and increased estrous cycle length F1 females. Sperm motility in
the 250 ppm group of F1 males was slightly reduced (84.8%) compared to
the control group (88.9%). The difference was statistically significant
(p<0.05). The study authors noted, however, that the sperm motility
percentage for F1 males was slightly higher than the mean value in the
WIL Research Laboratories historical control data (83.2%). Therefore,
the authors did not attribute the reduction in sperm motility to
exposure to nPB at 250 ppm. Male reproductive effects were consistent
with those identified in the Japanese studies previously cited
(Ichihara et al., 1998, 1999, 2000a; Wang, 1999).
Liver effects similar to those reported in the ClinTrials (1997b)
90-day inhalation study were observed in males and females in both
generations. Increases in liver weights occurred in both sexes
following exposure to 500 ppm; corresponding increases in the incidence
of minimal to mild hepatocellular vacuolation were observed at 250 ppm
in males and 500 ppm in females. The adverse effects on the central and
peripheral nervous system reported by Yu (2001) and Ichihara (1999,
2000b) occurred at higher doses than those associated with reproductive
and liver effects in the two-generation study.
Carcinogenicity/Mutagenicity. Limited in vitro screening assays
testing for mutagenicity and potential carcinogenicity have been
conducted on nPB. Two studies have been performed investigating the
potential mutagenicity of nPB in bacterial strains. Barber et al.
(1981) exposed five S. typhimurium strains (TA98, TA100, TA1535, TA1537
and TA1538) to five different vapor concentrations of nPB ranging from
1.1 to 20.3 [mu]mol/plate (135-2497 [mu]g/plate). Exposures were
performed in a closed incubation system in the presence and absence of
liver S9 fraction (from Arochlor-induced rats). Increases in revertants
were observed in only strains TA100 and TA1535 in both the absence and
presence of S9; increases were not reported in the other strains. Elf
Atochem (1994) exposed the same bacterial strains to nPB concentrations
of 100 to 100,000 [mu]g/plate in both the absence and presence of liver
S9 (from male Sprague-Dawley rats induced with Arochlor 1254). This
protocol also used a closed system (closed stainless-steel vessels).
The highest concentration was slightly cytotoxic; however, this assay
did test up to the limit dose (5,000 [mu]g/plate) recommended for
bacterial reversion assays. Appropriate positive and negative controls
were used to determine spontaneous background revertant frequency. No
increases in revertants were reported in any strain or condition. Given
these conflicting studies, the current data regarding mutagenicity of
nPB in bacterial strains are equivocal. Unpublished studies of in vivo
micronucleus formation (Elf Atochem 1995a) indicate that nPB is not
clastogenic, and a published dominant lethal assay with NPB was
negative (Saito-Suzuki et al. 1982).
In a cell death bioassay using cultured human liver cells (HepG2
hepatoma), the cytotoxicity of nPB was evaluated at concentrations
<=500 ppm (SLR 2001a). Results of the bioassay indicated that nPB was
cytotoxic (measured as decreased cell viability) at the highest
concentration tested (500 ppm). There were no positive responses
reported at any concentration for tests that evaluated enzyme function,
DNA damage, or DNA damage and repair when tested at concentrations up
to 500 ppm. A closely related compound, ethyl bromide, is weakly
carcinogenic in rodents (Haseman and Lockhart 1994), and iPB has been
shown to induce reverse mutations in bacteria (Maeng and Yu 1997).
Results from these screening assays for short-term genotoxicity do not
suggest significant concerns regarding nPB's potential carcinogenicity,
although more data are needed.
The National Institute of Environmental Health Sciences' National
Toxicology Program (NTP) is planning to conduct carcinogenicity studies
in both sexes of rats and mice, which will allow for more definitive
conclusions. To date, the NTP has not initiated new experimental
studies on nPB, and the data will not be available for several years.
[[Page 33292]]
b. Derivation of an AEL for nPB.
Benchmark Dose Modeling Background. EPA considered two methods to
derive a recommended acceptable exposure level for workplace exposure:
(1) The use of the no-observed-adverse-effect level (NOAEL) to define
the starting point of departure (POD) for the computation of a
reference value, and (2) the use of benchmark dose-response (BMD)
modeling to define the POD. Both methods are essentially a two-step
process, the first step defining a POD, and then the second
extrapolating from the POD to a lower, environmentally relevant
exposure level. EPA's in-depth analysis uses the BMD modeling approach,
for reasons explained below; however, under either approach, one
arrives at a similar value.
The traditional approach to derive safe exposure limits for
numerous chemicals regulated in a variety of programs, including the
SNAP program, has been to first determine the NOAEL (or LOAEL if a
NOAEL cannot be identified), use the NOAEL as the POD, and then apply
uncertainty factors based on EPA's guidelines to determine an
appropriate reference value. Using the NOAEL to determine a reference
value has long been recognized as having limitations in that it: (1) Is
limited to one of the doses in the study; (2) does not account for
variability in the estimate of the dose-response, which is due to the
characteristics of the study design; (3) does not account for the slope
of the dose-response curve; and (4) cannot be applied when there is no
NOAEL, except through the application of an additional uncertainty
factor (Crump, 1984; Kimmel and Gaylor, 1988).
A newer analytic approach is to use benchmark dose modeling to
define a point of departure for deriving a reference value or slope
factor that is more independent of study design. For risk assessment of
nPB, EPA followed the BMD guidelines to develop an AEL. The EPA Risk
Assessment Forum has written guidelines for the use of the BMD approach
in the assessment of non-cancer health risk (USEPA, 1995b), and the EPA
Benchmark Dose Workgroup is in the process of drafting technical
guidance for the application of the BMD approach in cancer and non-
cancer dose-response assessments. Use of BMD methods involve fitting
mathematical models to dose-response data and using the results to
select a BMD that is associated with a predetermined benchmark response
(BMR) at the low end of the observed range in the studies used, such as
a 10% increase in the incidence of a particular lesion or a 10%
decrease in body weight gain. The BMD derived from mathematical
modeling is the central estimate of the dose/exposure associated with
the BMR. The point of departure derived from BMD modeling, however, is
the Benchmark Dose Lowerbound (BMDL), or the lower 95% bound on the
dose/exposure associated with the BMR. Using the lower bound accounts
for the uncertainty inherent in a given study (e.g., small sample
size), and assures (with 95% statistical confidence) that the desired
BMR is not exceeded.
The advantage of the benchmark dose approach is that it considers
response data across all exposure groups. For example, a benchmark dose
can be calculated even in studies where a NOAEL could not be
identified, i.e., in studies where responses even in the lowest
exposure group tested were considered adverse. Unlike the NOAEL/LOAEL,
the benchmark dose does not have to be one of the exposure levels (dose
groups) chosen in the experimental design. In a hypothetical experiment
where groups of rats are exposed to a chemical at 0 ppm, 100 ppm, 500
ppm and 1,000 ppm, the NOAEL or LOAEL must be either 100 ppm, 500 ppm,
or 1,000 ppm simply because those were the only levels tested in the
experiment. However, the benchmark dose derived from the data in the
same experiment could be 200 ppm, 750 ppm, or even 997 ppm depending on
the shape of the dose response curve described by the data. EPA uses
the BMD approach whenever possible because it provides a more
quantitative alternative to identification of a point of departure than
the traditional NOAEL/LOAEL approach (US EPA 1995b).
Dosimetric adjustments and application of uncertainty factors.
Under either approach--NOAEL/LOAEL or BMD modeling--an adjustment to
the point of departure for the calculation of a reference value may be
necessary to calculate a ``human equivalent concentration'' (HEC) if
there are differences between the exposure regime used in the toxicity
studies and a typical workweek of 8 hours per day and 5 days per week.
Once a POD and the corresponding HEC is identified, uncertainty factors
(UFs) are applied to account for extrapolation uncertainties that could
underestimate the chemical's toxicity potential for exposed humans (in
this case, workers using nPB). According to standard risk assessment
methods as delineated in Agency guidance (US EPA, 1994), UFs of up to
10 may be applied for each of the following conditions:
(1) Data from animal studies are used to estimate effects on
humans;
(2) Data on healthy people or animals are adjusted to account for
variations in sensitivity among members of the human population (e.g.,
interindividual variability);
(3) Data from subchronic studies are used to provide estimates for
chronic exposure;
(4) Studies that only provide a lowest observed adverse effect
level (LOAEL) rather than a no observed adverse effect level (NOAEL) or
benchmark dose; or
(5) An incomplete data base of toxicity information exists for the
chemical (US EPA, 1995b).
Finally, a modifying factor (MF), which is an additional
uncertainty factor that is greater than zero and less than or equal to
10, may be used. The magnitude of the MF depends upon the professional
assessment of scientific uncertainties of the study and data base not
explicitly treated above, e.g., the completeness of the overall data
base and the number of species tested. The default value for the MF is
1.
It is important to note that EPA does not have specific guidelines
for occupational studies. As such, EPA is applying its general risk
assessment principles and adapting its methodologies, as appropriate to
consider risk in an occupational setting. For example, as mentioned
above, EPA is adjusting its exposure scenario to derive a human
equivalent concentration (HEC) that is representative of workplace
exposure, rather than continuous lifetime exposure.
Selection of Endpoints for Benchmark Dose Modeling. Based on EPA
guidance, endpoints were selected for BMD analysis and for potential
use as a point of departure using the following principles:
[sbull] Toxicological significance of the endpoint
[sbull] Relevance to humans
[sbull] Quality of study and dose-response data
[sbull] Reproducibility of effects across multiple studies.
EPA selected reduced sperm motility and increased liver vacuolation
for BMD analysis because they met the above criteria, and because these
effects were seen consistently throughout the toxicological database at
low exposures. EPA guidance states that endpoints selected as
appropriate for risk assessment should be modeled if their LOAEL is up
to 10-fold above the lowest LOAEL. This ensures that no endpoints with
the potential to have the lowest BMDL are excluded from the analysis.
The selection of the most appropriate
[[Page 33293]]
BMDs to use for determining the point of departure must be made by the
risk assessor using scientific judgement and principles of risk
assessment, as well as the results of the modeling process.
Toxicological Evaluation for AEL Derivation. Benchmark dose
modeling was conducted following EPA guidelines. EPA modeled six data
sets for liver vacuolation and reduced sperm motility based on results
from two studies to identify the lowest BMDL as a point of departure
(POD).\7\ EPA selected these endpoints for BMD analysis because they
were consistently found to be the most sensitive effect across the many
studies that were conducted on the compound. Further, these particular
studies provided robust data on these endpoints so that BMD analysis
could be conducted. Based on this analysis, sperm motility in the F1
males from the WIL (2001) study was selected as the POD as it would be
protective for all effects of nPB. SLR conducted a BMD analysis using
data sets for numerous endpoints from 5 studies, including the WIL
(2000) and ClinTrials (1997b) studies used by EPA (SLR International
Corp., 2001b).\8\ SLR also identified sperm motility in F1 males from
the WIL (2001) study as the lowest BMDL. The SLR BMD analysis is
discussed further in section IV.A.1.d. The methods used in development
of the AEL based on sperm motility are described below. It is important
to note that the animals in the 2-generation study were dosed every day
for six hours. As such, the dosing scenario used for the testing
procedure does not exactly mirror the human exposure scenario in the
workplace of 8 hours per day 5 days per week. However, it is still
appropriate to consider the data because they address the most
sensitive health endpoints, and because the BMDL is adjusted by
deriving a HEC to account for workplace exposures. A more complete
discussion of EPA's adjustment of the BMDL is contained in ICF, 2002a.
---------------------------------------------------------------------------
\7\ Data sets that were modeled from the WIL study include sperm
motility and liver vacuolation in the F0 and F1 generations. Data
sets modeled from ClinTrials (1997b) were liver vacuolation in both
males and females.
\8\ SLR International Corp. (2001b) conducted BMD modeling on
the following studies: ClinTrials (1997a), ClinTrials (1997b),
Ichihara, et al. (2000a and b), and WIL (2001). Reproductive
endpoints modeled included sperm count, retained sperm in
seminiferous tubules, sperm deformities, sperm motility, epididymal
sperm count, fertility index, litter viability, and plasma glucose
levels. Other toxicological endpoints modeled included forelimb
strength, hind limb strength, motor conduction velocity, distal
latency time, plasma creatinine phosphokinase levels, brain cell
vacuolation, liver vacuolation in males, and analysis in various
parameters associated with effects on blood formation.
---------------------------------------------------------------------------
EPA did not use neurotoxic effects as endpoints for deriving an AEL
value since we did not consider this to be one of the most sensitive
endpoints. No neurotoxic effects were reported in the 2-generation
reproductive toxicity assay (WIL, 2001), and no adverse effects were
observed in the functional observational battery analysis, either in an
abbreviated form in the 28-day study at exposure concentrations of 400
and 1,000 ppm (ClinTrials, 1997a), nor in the 90-day study at
concentrations of 400 and 600 ppm (ClinTrials, 1997b). Although the
NIOSH voluntary medical survey performed in 1999 attempted to assess
symptoms of neurotoxic effects, no exposure-response trend for headache
or other neurological effects could be identified from the data.
The vacuolation of the white brain matter that was observed in the
28-day study at all exposure concentrations was not observed in the 90-
day study, indicating that this effect may be a transient response and
not adverse. Further, the vacuolation was not dose-dependent and did
not correlate with other gross CNS effects observed at 1,600 ppm in the
28-day study. In the 2-generation study, clinical signs were monitored
and CNS effects were not observed at any exposure concentration (0,
100, 250, 500, and 750 ppm) in the F0 or F1 animals, nor were
histopathologic lesions observed in the brain, spinal cord or
peripheral (sciatic) nerve of rats in the 750-ppm group of the F0
generation in the 2-generation study or in the F1 population.
EPA's Benchmark Dose Software (BMDS) was used for model fitting and
BMD and BMDL estimation. To derive a BMD and BMDL for reduced sperm
motility in the F0 and F1 males from WIL (2001), the data were modeled
as continuous effects. Following EPA's Benchmark Dose guidelines, BMDs
and BMDLs were defined based on benchmark responses (BMRs) of 10% extra
risk--that is, the level at which 10% of the animals would show adverse
effects for a particular endpoint. BMDLs were defined as the 95% lower
confidence bound on the corresponding BMD estimates. Confidence bounds
were calculated by BMDS using a likelihood profile method. The data
sets for the reduced sperm motility endpoint were quantitatively
summarized by group means and measures of variability (standard errors
or standard deviations). The models used to represent the dose-response
behavior of these continuous endpoints are those implemented in EPA's
Benchmark Dose Software which are the Power model, the Hill model, and
the polynomial model. Goodness-of-fit for each model for a given data
set was determined based on a likelihood ratio statistic. In
particular, maximized log-likelihoods associated with the modeling were
sequentially compared.
Based on the criteria below, the most appropriate mathematical
model and its corresponding BMDL was chosen as the best fit for each of
the data sets modeled:
1. Models with an unacceptable fit (including consideration of
local fit in the low-dose region) were excluded. Visual fit,
particularly in the low-dose region, was assessed for models that had
acceptable global goodness-of-fit.
2. If the BMDL values for the remaining models for a given endpoint
were within a factor of 3, no model dependence was assumed, and the
models were considered indistinguishable in the context of the
precision of the methods. The models were then ranked according to the
Akaike Information Criterion (AIC), which is reported by the BMDS
software to aid in comparing the fit of different models. The model
with the lowest AIC (within the family of models) was chosen as the
basis for the BMDL.
3. If the BMDL values were not within a factor of 3, some model
dependence was assumed, and the lowest BMDL was selected as a
reasonable conservative estimate, unless it was an outlier compared to
the results from all of the other models. Note that when outliers are
removed, the remaining BMDLs may then be within a factor of 3, and so
the criteria given in item 2 would be applied.
BMDs for reduced sperm motility in F1 and F0 males were 276 ppm and
362 ppm respectively, and BMDLs were 169 ppm and 282 ppm. Consistent
with EPA risk assessment guidance, the BMDL of 169 ppm for reduced
sperm motility in F1 males (WIL, 2001) was selected as the POD. EPA
considered whether a BMDL derived from the F1 generation should be used
to determine a workplace exposure limit, particularly in relation to
the potential mechanisms by which nPB exerts its effects on the
reproductive system. While some mechanistic data are available on this
subject, they are inconclusive and limited. The available data do not
rule out the possibility that the effects on the F1 generation occurred
as a result of effects on parental germ cells (sperm or ova) or effects
mediated by changes to the endocrine system. Because of the lack of
mechanistic data on developmental and potential transgenerational
effects, it is most appropriate and protective, as well as consistent
with EPA risk assessment
[[Page 33294]]
guidelines, to use the endpoint observed at the lowest effect level to
derive the AEL. In this case, that endpoint is decreased sperm motility
in the F1 generation.
The BMDL was multiplied by 6/8 and 7/5 in order to derive the HEC,
which accounts for temporal differences between the exposure duration
used in the study (6 hours per day, 7 days per week) and an 8-hour per
day, 5-day work week. This results in a HEC for spermatic effects of
177 ppm. Uncertainty factors were then applied to the HEC, taking into
account the following considerations listed below.
(1) An uncertainty factor is needed to account for physiological
differences between humans and rats. EPA reference concentration (RfC)
guidelines describe the factors that must be considered and state that
an uncertainty factor 10 may be used for potential differences between
study animals and humans. This factor of 10 is often thought to consist
of two uncertainty factors of 3--the first to account for differences
in pharmacokinetics \9\ and another uncertainty factor to account for
differences in pharmacodynamics \10\ between the study animal and
humans. (The value of 3 is the closest whole number to the square root
of 10.) According to EPA RfC guidelines, no adjustment for differences
in pharmacokinetics is necessary in this case since the blood/air
partition coefficient \11\ for nPB in the human (7.1) is less than in
the rat (11.7), indicating that the delivered dose of nPB into the
bloodstream in rats is slightly higher than in humans.
---------------------------------------------------------------------------
\9\ Pharmacokinetics refers to the activity or fate of chemicals
in the body, including the processes of absorption, distribution,
localization in tissues, biotransformation, and excretion.
\10\ Pharmacodynamics refers to the biochemical and
physiological effects of chemicals in the body and the mechanisms of
their actions.
\11\ A ratio of a chemical's concentration between blood and air
when at equilibrium.
---------------------------------------------------------------------------
However, EPA recognizes that the lack of an uncertainty adjustment
for pharmacokinetic differences between animals and humans rests on a
default approach applied to category 3 gases described in Appendix J of
its guidelines for deriving an inhalation RfC. This default approach
assumes that the pharmacokinetics of nPB conform to a model that
requires several assumptions, in particular: (1) The toxicity is
directly related to the inhaled parent compound in the arterial blood,
and (2) the critical metabolic pathways scale across species, with
respect to body weight, in the same way as the ventilation rate (e.g.,
BW\3/4\). Given the hypothesized metabolic pathways for nPB
(ICF, 2002a; CERHR, 2002a), it is plausible that toxicity in rats may
be related to a reactive metabolite in the target tissue rather than
the blood level of the parent compound. EPA is not aware of any
quantitative data on nPB metabolism in humans, or evidence implicating
the biologically active agent or mode of action. EPA requests
additional data and comment from the public on nPB pharmacokinetics,
metabolism, and mode of action that will help determine whether an
interspecies uncertainty factor greater than 1 is appropriate to
account for pharmacokinetics. If data become available indicating that
nPB does not conform to the constraints assumed by the default
pharmacokinetic model in the RfC guidelines, EPA would refine its risk
assessment for nPB as necessary, and apply an uncertainty factor for
pharmacokinetics in extrapolating from animal to humans. We would also
revise our acceptability determinations accordingly.
With regard to the UF for pharmacodynamics, no data exist to
compare the effect of nPB on human spermatocytes and rat spermatocytes.
EPA does not have data suggesting that the default of 3 for
pharmacodynamics should not be used. Thus, the full uncertainty factor
of 3 for differences in pharmacodynamics was applied. EPA also requests
comments and data on this uncertainty factor.
(2) Although workers employed in the types of industrial sectors
that are part of this SNAP review likely represent a generally healthy
population, pre-existing reproductive conditions as well as general
variability in fertility would not impact a worker's overt health or
employment status, and would be largely unobserved. It is estimated
that 6% of adult males are infertile (Purves, 1992), and that 40%-90%
of these cases are due to deficient sperm production of unidentifiable
origin (Griffin, 1994). Given this information, EPA concludes that a
significant portion of the male population has pre-existing
reproductive deficits. EPA's risk guidelines for deriving community-
based reference concentrations recommend a factor of 10 in accounting
for intraspecies variability. EPA believes that in the case of nPB, a
lower uncertainty factor is appropriate to account for variability
within the worker population. This UF is intended to protect for
potential ``unobserved'' reproductive medical conditions (e.g.,
decreased sperm motility, aberrant sperm formation) that are known to
exist among otherwise healthy males of working age. Because we are
concerned about exposures in the workplace, not exposures to the full
population, and because exposures would not be continuous, such as
would be expected when developing an RfC, we employed an UF of three as
an upper bound instead of the full uncertainty factor of 10 for
intrahuman variability.
The following equation describes how EPA derives 18 ppm as a
starting point in the development of a recommended AEL using a UF of 3
for variations in the human population, and 3 for pharmacodynamics:
169 ppm * \6/8\ * \7/5\ * \1/3\ * \1/3\) = 18 ppm
This derivation rests on assumptions that some may consider
conservative, including the use of the F1 generation as the point of
departure for workplace exposure, and the fact that reduced sperm
motility may be a particularly sensitive endpoint for male reproductive
effects. For a further discussion, see the next section below, ``AEL
adjustment based on risk management principles.''
AEL adjustment based on risk management principles. Risk management
uses risk characterization, along with directives of the enabling
regulatory legislation and other factors, to decide whether to control
exposure to the suspected agent and the level of control. Risk
management decisions also consider socioeconomic, technical, and
political factors (EPA Reproductive Risk Assessment Guidelines, 1996).
Unlike many other chemicals being reviewed by SNAP, nPB is already in
use. Therefore, a decision on the AEL that incorporates risk management
considerations may be appropriate. Doing so is consistent with one of
the original ``Guiding Principles'' of the SNAP program (59 FR 13046,
March 18, 1994):
EPA does not intend to restrict a substitute if it poses only
marginally greater risk than another substitute. Drawing fine
distinctions concerning the acceptability of substitutes would be
extremely difficult given the variability in how each substitute can
be used within a specific application and the resulting
uncertainties surrounding potential health and environmental
effects. The Agency also does not want to intercede in the market's
choice of available substitutes, unless a substitute has been
proposed or is being used that is clearly more harmful to human
health and the environment than other alternatives.
If EPA adopted 18 ppm as the AEL, we would likely propose that use
of nPB be listed as unacceptable in adhesives applications, based on
data indicating that exposure to nPB in such uses regularly exceed 18
ppm on average. However, EPA has determined that adhesive operations
can meet an AEL of 25 ppm with proper ventilation and
[[Page 33295]]
controls (see Section IV.A.1.e., ``Feasibility of meeting the AEL for
nPB in each industrial sector''). The AEL of 18 ppm was derived using
assumptions that some may consider conservative. Following the SNAP
principle referenced above, some slight adjustment of the AEL may be
warranted after applying judgment based on the available data, and
after considering alternative derivations.
To assess how much of an adjustment may be appropriate that would
still be protective of human health, EPA considered potential sources
of conservatism in the AEL derivation--specifically, the use of the
BMDL in the F1 generation as a point of departure. To assess the
magnitude of this conservatism, we derived an AEL based on the BMDL for
reduced sperm motility in the F0 generation (282 ppm), the second most
sensitive endpoint found in the 2-generation study. Deriving an HEC
(296 ppm), and applying the same uncertainty factors as applied to the
F1 generation (3 for intraspecies variability and 3 for differences in
pharmacodynamics), would result in an occupational exposure limit of
approximately 30 ppm. A derivation based on F0 data could be considered
as a reasonable and protective upper bound for the occupational
exposure limit. EPA requests comment on whether it appropriate to
interpret 30 ppm as an upper bound for an occupational exposure limit.
EPA has determined that 18 ppm is a reasonable but possibly
conservative starting point, and that exposure to 25 ppm would not pose
substantially greater risks, while still falling below an upper bound
on the occupation exposure limit. An AEL of 25 ppm would reduce overall
risk to worker health while adhering to EPA's SNAP guiding principle of
not finding a substitute unacceptable unless the proposed substitute is
clearly more harmful than other alternatives. EPA specifically requests
comment on this approach.
Dermal Exposure. EPA believes that workers should use good
workplace practices and proper handling procedures to avoid unnecessary
dermal exposure to all industrial solvents, including nPB. Similar to
other halogenated solvents, nPB may defat the skin and may cause local
irritation due to this characteristic. A skin notation is applied to
those chemicals where ``dermal absorption contributes substantially to
the overall systemic toxicity'' (skin notation documentation for methyl
chloride; ACGIH, 1991). As described previously, the available acute
dermal toxicity study in rats (Elf Atochem, 1995) indicates that acute
dermal exposure to nPB does not result in systemic toxicity. Because
significant dermal absorption of nPB was not demonstrated in this
study, EPA is not including a skin notation for nPB along with our
recommended AEL in the comments section of the regulatory text. The
database regarding dermal toxicity for nPB is not as conclusive as the
data for chemicals that have a skin notation, (e.g., methyl chloride,
dichlorvos). To apply a skin notation to nPB would imply that the
dermal toxicity of this compound is similar to that of these other
compounds. It is also noteworthy that there is no skin notation for
other halogenated solvents such as methylene chloride or
perchloroethylene, and there is no evidence that absorption through the
skin is greater for nPB than for the other halogenated compounds. Thus,
in EPA's judgement the database currently does not support the need for
a skin notation for nPB.
However, we note that the acute dermal study did not provide
information regarding chronic dermal absorption. Further, NIOSH
evaluated the potential of nPB to permeate skin and promote chronic,
systemic toxicity using a mathematical model and the log octanol::water
coefficient for nPB, which is approximately 2. This evaluation found
that nPB dermal exposure may be an additional source of exposure to
workers if the unprotected skin of both hands is exposed (NIOSH, 2003).
Given the above information, EPA specifically requests comment on
whether to add a skin notation to our recommended AEL in the final rule
if there are data that support this change.
c. Overview of the Evaluation of Risks to Human Reproduction
(CERHR) Expert Panel Report on nPB. In December 1999, NIOSH submitted
an assessment nomination to the National Toxicology Program's (NTP)
Center for the Evaluation of Risks to Human Reproduction (CERHR) for
both nPB and iPB. The NTP and the National Institute of Environmental
Health Sciences (NIEHS) established CERHR in June 1998. CERHR's purpose
is to provide timely, unbiased, scientifically sound evaluations of
human and experimental evidence for adverse effects on reproduction,
including development, caused by agents to which humans may be exposed.
nPB (1-Bromopropane) was nominated by NIOSH and selected for
evaluation by the CERHR based primarily on documented evidence of
worker exposures and published evidence of reproductive and
developmental toxicity in rodents (this evidence is reviewed above in
section IV.A.1.a). The evaluation of nPB was a four-month effort by a
ten-member Expert Panel of academic, private and government scientists
that culminated in a public meeting in December 2001. At that meeting,
the Expert Panel reviewed the scientific evidence on nPB and reached
conclusions regarding its potential effects on human reproduction and
development. The Expert Panel Report on nPB was issued in March 2002
(CERHR, 2002a). An Expert Panel Report on iPB was issued at the same
time and is discussed in section IV.A.4. of this preamble (CERHR,
2002b).
The Expert Panel Report on nPB is intended to: (1) Interpret the
strength of scientific evidence that a given exposure or exposure
circumstance may pose a hazard to reproduction and the health and
welfare of children; (2) provide objective and scientifically thorough
assessments of the scientific evidence that adverse reproductive/
developmental health effects are associated with exposure to specific
chemicals or classes of chemicals, including descriptions of any
uncertainties that would diminish confidence in assessment of risks;
and (3) identify knowledge gaps to help establish research and testing
priorities.
NTP-CERHR sought public comment on the Expert Panel Report through
a Federal Register notice on March 8, 2002 (67 FR 10734). The NTP has
issued a final report, and has published all the public comments that
were received on that report. These documents may be accessed through
the CERHR Web site at http://cerhr.niehs.nih.gov/news/bromo/index.html.
The conclusions of the March 2002 Expert Panel Report on nPB were
as follows:
[sbull] Available human data are insufficient to draw conclusions
on the potential for reproductive or developmental toxicity.
[sbull] Available toxicological data were sufficient to conclude
that nPB exposure can induce developmental and reproductive toxicity in
rats. In evaluating the potential effects on human reproduction, the
rat data are assumed to be relevant for humans.
[sbull] The mechanisms that lead to reproductive or developmental
toxicity are unknown.
[sbull] There are no relevant kinetic or metabolism data for nPB to
compare human and animal exposure levels.
The Expert Panel identified LOAELs from the body of animal data as
follows:
[sbull] A LOAEL for male reproductive effects of 200 ppm based on
decreases in absolute and relative seminal vesicle weight reported in
Ichihara (2000b). A
[[Page 33296]]
NOAEL of 100 ppm was identified based on decreases in prostate weight
observed at 250 ppm in WIL (2001).
[sbull] A LOAEL of 250 ppm, and a NOAEL of 100 ppm for female
reproduction based on increased estrous cycle length in WIL (2001).
[sbull] A LOAEL of 250 ppm and a NOAEL of 100 ppm for
mineralization of the kidney pelvis in both F0 and F1 generations,
based on WIL (2001).
EPA agrees with the panel's conclusions that the available human
data are insufficient to draw conclusions on the reproductive or
developmental toxicity of nPB and that the mechanisms that lead to
reproductive or developmental toxicity are unknown. EPA also agrees
with the panel that a NOAEL for reproductive effects (male) would be
considered to be 100 ppm under a traditional risk assessment analysis.
However, based on the criteria described previously for selecting
endpoints for BMDL analysis, we believe the CERHR endpoints are not
appropriate for developing the AEL for nPB, as explained below.
Reduced seminal vesicle weight. EPA did not conduct BMD analysis
for reduced seminal vesicle weight observed in the Ichihara (2000b)
study because there is no consistency of effect across available
studies for this endpoint. Reduced seminal vesicle weight was not found
to be a sensitive endpoint in WIL (2001). In fact, a statistically
significant reduction in seminal vesicle weight was only seen in the
750 ppm group in the F0 generation, and there were no statistically
significant effects on seminal vesicle weight in the F1 generation.
Because there were other endpoints that were more sensitive in the WIL
study, we regard those endpoints to be of greater toxicological
importance. Further, EPA believes that because the Ichihara study was
not performed according to GLP guidelines, and there were conflicting
reports regarding the exposure regime and the number of animals used,
it is not appropriate to use this study in quantitative risk
assessment.
Reduced absolute prostate weight. Based on the WIL study, the CERHR
Expert Panel identified a NOAEL of 100 (with a LOAEL of 250) for
reduced absolute prostate weight in the F0 males. The toxicological
relevance of absolute prostate weight reduction is questionable since
this endpoint may be associated with reduction in overall weight gain.
To assess the significance of this particular endpoint, EPA calculated
the mean relative prostate weights for exposed dose groups from the WIL
(2001) study. Relative prostate weights (organ weight/body weight) in
F0 males were 0.0040, 0.0039, 0.0036, 0.0035, and 0.0035 at 0, 100,
250, 500, and 750 ppm respectively, revealing that relative prostate
weight at exposures greater than or equal to 250 ppm decreased only 10%
relative to controls. Because the dose-response relationship in other
endpoints was more pronounced, EPA did not conduct BMD modeling on this
endpoint.
Increased estrous cycle length. The Expert Panel identified 250 ppm
as a LOAEL for females based on increased estrous cycle length in the
F1 generation of the WIL (2001) study. EPA agrees that the slight
increase in estrous cycle length may be a result of nPB exposure.
However, because the estrous cycle length of 4.9 days at 250 ppm is
within the range of historical controls, the effect cannot be
conclusively attributed to exposure without statistical analysis. The
study report also notes lack of cycling in some females, which may have
caused difficulty in accurately determining the average estrous cycle
length for each affected group. Because these data are lacking, this
endpoint should not be used for developing the AEL.
Mineralization of the kidney pelvis. The Expert Panel concluded
that mineralization of the pelvis of the kidneys at 250 ppm was an
adverse effect. EPA notes that mineralization of the kidney was not
consistently associated with nPB exposure across different studies, and
that in WIL (2001) the severity of mineralization did not increase
above a category of minimal except at 750 ppm where it was mild.
Therefore, EPA did not consider using this endpoint as useful for
developing the AEL.
Sperm Motility. The Expert Panel identified 500 ppm as the LOAEL
for reduced sperm motility. The Panel agreed with the WIL (2001) study
authors that the slight but statistically significant reduction in the
percentage of motile sperm in the F1 males at 250 ppm (85% vs. 89% in
concurrent control animals) could not be attributed to nPB exposure
since the percentage of motile sperm in this dose group slightly
exceeded that of historic controls (83%). The data indicate that the
small changes observed at 250 ppm are consistent with larger changes in
sperm motility observed at 500 and 750 ppm. Thus, results for sperm
motility in F0 and F1 males exhibited dose-related trends, and
conformed to other principles for the selection of endpoints for BMD
analysis (See earlier discussion in section IV.A.1.b.). Thus,
regardless of whether a LOAEL of 500 ppm or 250 ppm is assigned to this
particular endpoint, the Agency determined that reduction in the
percentage of motile sperm in the F1 males is a good candidate for BMD
analysis. In addition, it is important to note that the Panel did not
have access to either the ICF or SLR International benchmark dose
analyses. As discussed in section IV.A.1.b, benchmark dose modeling
overcomes the issue of drawing a ``bright line'' in the form of a LOAEL
or NOAEL and instead uses the full set of data across all exposure
levels (ICF, Inc., 2002a; SLR International, 2001b). Using the results
of benchmark dose modeling, it becomes clear that sperm motility is a
sensitive effect, and is an appropriate effect upon which to base an
AEL.
d. AELs suggested by other reviewers and outside parties. In the
draft final nPB risk screen conducted for EPA in preparation for
today's proposal, ICF Consulting states that ``Given the strength of
the data base and the extrapolation of the data to occupational
exposures, a range of uncertainty factors to account for variability in
the human population of 2 to 3 is considered appropriate.'' (ICF,
2002a). EPA recognizes that the choice of UF relates to a wide range of
considerations including the strength of the data base. Applying a
range of UFs between 2 and 3 to account for intrahuman variability
would yield a range of occupational exposure limits between 18 and 30
ppm. ICF suggested that the midpoint of this range, 25 ppm, was an
appropriate occupational limit value for the purposes of the risk
screen for nPB. EPA requests comment on this recommended approach in
deriving an occupational exposure limit, including the application of
uncertainty factors.
EPA's Office of Atmospheric Programs solicited comments regarding
ICF Consulting's analysis and derivation of a recommended AEL from
EPA's Office of Research and Development (ORD), external toxicologist
William Brock, external toxicologist Darol Dodd, and the State of
California, Department of Health Services, Hazard Evaluation System &
Information Service (HESIS). The comments are available in docket A-
2001-07.
ORD's comments focused on the WIL Research Laboratories two-
generation study and its use in identifying sensitive endpoints. ORD
noted that the study's results indicated dose-related trends, that a
number of endpoints were significantly affected at 500 ppm in both
generations, and there were slight--though in most cases not
statistically significant--decreases at 250 ppm and even 100 ppm for
some endpoints. They also stated that ``[i]n the absence of evidence of
dominant lethality or trans-generational effects typical of endocrine
[[Page 33297]]
disrupting chemicals, it is reasonable to conclude that the effects of
[nPB] are elicited in both sexes via their exposure as adults.'' They
also noted that ``the modest degree of change in the 250 ppm F1 sperm
motility endpoint (and lack of significance in the F0 at this dose)
compared to the collective more robust changes at 500 ppm, in both the
F0 and F1, indicates that 250 ppm could reasonably be considered a
NOAEL for nPB, with 500 ppm being a LOAEL.'' Finally, ORD noted that
``even if the F1 data may not be directly applicable for occupational
exposures in males, it certainly is applicable to occupational
exposures of pregnant women.'' They conclude with suggestions for
further research (Klinefelter and Darney, 2002).
EPA asked William Brock to review the draft AEL report from a
general toxicological point of view. Dr. Brock is currently a senior
manager with Environ Corporation. In his review, Dr. Brock noted that
several subchronic studies in rats have been conducted with nPB with
concentrations ranging from approximately 100 ppm to 1800 ppm.
Biological effects have been on liver, male reproductive tissue, and,
to some extent, hematological parameters. Although some of the studies
have not been conducted according to GLP, this fact does not
necessarily limit the usefulness of the studies to recommend an
exposure limit. Overall, the sperm effect observed at 400 ppm and the
effects on fertility at 500 ppm with hepatic vacuolation at 250
represent the PODs for setting exposure limits for nPB. The NOAEL for
these effects would be 200 ppm. Dr. Brock notes that ``exposure limits
that have historically been established are generally, but no[t]
always, an order of magnitude below the NOAEL. Taking this approach
would result in an occupational limit of 20 ppm (200/10). Although the
ICF report could be improved by being more specific on effects and
concentrations, the logic provided in the report and the end result,
i.e., a 25 ppm exposure limit, is certainly justified'' (Brock, 2002).
EPA asked Darol Dodd to review and comment on the draft AEL report
(ICF, 2000a). Dr. Dodd is currently the Laboratory Director for ManTech
Environmental Technology, Inc. In his comments, Dr. Dodd stated that
the ICF report provided logical and consistent explanations for
selection of the BMDL and uncertainty factors. He noted that several of
the studies show LOAEL or NOAEL values at 200 ppm to 250 ppm. In his
opinion, ``a recommended AEL value that is about one order of magnitude
lower than LOAELs/NOAELs in a number of laboratory rodent studies does
not appear to be overly protective'' (Dodd, 2002).
HESIS provided comments on the AEL derivation for nPB that focused
on the available studies useful for low-dose risk assessment,
identifying the LOAELs and NOAELs from these studies, and identifying
their disagreements with the ICF evaluation. Overall, HESIS took issue
with the approach used by ICF to derive an AEL: ``ICF repeatedly
ignores or discounts effects seen with low-level exposures. At most
points where a decision based on professional judgment must be made,
ICF makes the choice that leads to the highest possible AEL.'' HESIS
states that, contrary to the ICF approach, an appropriate risk
assessment methodology would take a NOAEL, LOAEL or appropriate BMDL,
and apply uncertainty factors of 10 for each of the following
conditions: (1) Interspecies variation, (2) intraspecies variation, (3)
reliance on a LOAEL rather than a NOAEL where necessary, and (4)
extrapolation from acute or subchronic exposure to chronic exposure.
The total uncertainty factor would be between 1,000 and 10,000. HESIS
stated that appropriate endpoints and points of departure would be
reduced pup weight seen in the Huntingdon (2001) study at 103 ppm, the
neurotoxicity seen in Ichihara (2000a) at 200 ppm, reduced seminal
vesicle weight and increase in tailless sperm seen at 200 ppm in
Ichihara (2001a), reduced sperm motility at 200 ppm in Wang (1999), CNS
pathology (vacuolation of white matter) at 400 ppm seen in ClinTrials
(1997a), and from the WIL (2001) study, reduced fertility observed at
100 ppm and other adverse reproductive and kidney effects observed at
250 ppm or the lowest BMDL calculated from all studies. Using any of
these points of departure, HESIS suggests that a reasonable AEL could
range from less than 0.05 ppm to less than 5 ppm, and recommends an AEL
of 1 ppm.
HESIS stated that, in deriving the AEL for the liver vacuolation,
ICF used no uncertainty factor for interspecies pharmacokinetic
variation, assuming ``without any basis, that gas exchange within the
lung constitutes the entire pharmacokinetic variation between the
species, simply because the blood-air partition coefficient is lower in
humans than in rats.'' HESIS also disagreed with the use of no
uncertainty factor for intraspecies variation for liver vacuolation.
With regard to ICF's derivation of an AEL for sperm motility, HESIS
disagreed with ICF's use of no uncertainty factor for interspecies
pharmacokinetic variation for the same reason given for liver
vacuolation. HESIS also stated that there ``is no data base at all on
which to determine the likelihood and degree of interhuman variability
in sensitivity to the spermatotoxic effect of [nPB] * * * .'' Finally,
HESIS stated that nPB ``is an organic solvent that is probably well
absorbed through the skin and should be listed with a skin notation * *
* .''
A response from ICF Consultants to HESIS's comments is included in
the docket (ICF 2002c). EPA concluded that the issues HESIS raises are,
in fact, questioning EPA's risk assessment guidelines that were the
basis for the AEL report, rather than comments unique to the AEL for
nPB. For example, EPA's risk assessment guidelines allow use of a
default uncertainty factor of 1 instead of 3 for pharmacokinetics for
nPB and other inhaled gases where the toxicity is from the parent
compound, rather than metabolites. As discussed above in section
IV.A.1.b, we request comment and data that would confirm or refute the
appropriateness of the assumptions in Appendix J of EPA's risk
assessment guidelines. In addition, EPA disagrees that the uncertainty
factor for variability in the worker population should be the same as
that for variability in the general population (10). Because the
working population does not include children or the elderly, as is the
case for the general population, we do not believe that a full UF of 10
for sensitive subpopulations is necessary. Further, workers are only
potentially exposed during a 40-hour workweek and not continuously, as
would be expected for the general population. Finally, because of the
length of the WIL Laboratories study, we do not believe that it is
necessary to add an uncertainty factor to extrapolate from subchronic
to chronic exposures.
Various chemical manufacturers and solvent formulators have derived
their own recommended industrial exposure limits. Albemarle Corporation
and Dead Sea Bromine Group, both of whom continue to produce nPB,
recommend an AEL of 25 ppm in their Material Data Safety Sheets. Great
Lakes Chemical and Atofina recommended AELs of 10 ppm and 5 ppm
respectively, although neither of these companies currently sells nPB.
Petroferm produces nPB formulations and recommends an exposure limit of
25 ppm. Finally, Enviro Tech International, Poly Systems International,
TULSTAR Products, and Amity International, all of whom produce nPB
formulations, recommend an exposure limit of 100 ppm.
In a November 6, 2000, meeting with EPA, Albemarle explained that
its derivation of a workplace exposure guideline of 25 ppm is based
upon raw
[[Page 33298]]
data from the two-generation reproductive study (WIL, 2001). In the
fall of 2000, Albemarle analyzed preliminary data from the two highest
exposure groups in two-generation study, 750 ppm and 500 ppm, and found
evidence of reproductive effects. As a proactive measure while
completing analysis of the data, Albemarle started with an exposure
level of 250 ppm and divided by a safety factor of 10, yielding an
exposure guideline of 25 ppm. EPA has not seen the derivation of Great
Lakes Chemical Corporation's workplace exposure guideline of 10 ppm or
Atofina's guideline of 5 ppm.
The AEL recommended by Enviro Tech International is based on two
separate analyses. In the first analysis, Rozman and Doull (2001)
recommend an AEL of 60-90 ppm based on the results obtained from a
health questionnaire administered as a part of a NIOSH Health Hazard
Evaluation at a site where nPB is used as an adhesive (NIOSH, 1999).
This AEL derivation was subsequently published in Applied Occupational
Environmental Hygiene, the ACGIH's journal, in 2002 (Rozman and Doull,
2002).
In their analysis, Rozman and Doull identified the most sensitive
endpoint for nPB toxicity as peripheral/central neurotoxicity followed
by reproductive toxicity and then liver toxicity. This ranking was
based on a subchronic inhalation study by Ichihara (2000b) in which
decreased hind limb strength in mice was observed following 4 weeks of
exposure at 200 ppm. Rozman and Doull concluded that rats are more
sensitive to reproductive effects of nPB than humans based on the NIOSH
health survey (NIOSH 2002b), which did not identify any statistically
significant reproductive effects in humans exposed to nPB. Based on the
NIOSH health survey data, conducted at a facility where nPB was used as
an adhesive solvent, Rozman and Doull identified 170 ppm as a no
observed effect level (NOEL) in workers who reported having a headache
more than once per week. They then applied a safety of 2 to protect
nearly all workers, and a safety factor of 3 to provide a larger margin
of safety from this adverse effect. This approach resulted in a
recommended industrial exposure guideline for nPB of 60-90 ppm.
EPA does not agree with Rozman and Doull's AEL recommendation.
First, their ranking of neurotoxicity as the most sensitive
toxicological endpoint fails to take into account that in the Ichihara
study, rats were dosed 8 hours per day for 12 weeks, while in the two-
generation study, animals were exposed to nPB for 6 hours per day.
Therefore, the exposure levels in the Ichihara study must be adjusted
by a factor of 0.75 in order to directly compare doses to the 2
generation study. If this adjustment is made, the LOAEL for the
Ichihara study becomes 266 ppm, higher than the LOAEL of 250 ppm for
reproductive and liver effects identified in the two-generation study.
Further, the results of the Ichihara study conflict with the results of
the 90-day inhalation study (ClinTrials, 1997b), in which decreases in
grip strength were not observed in rats exposed to levels up to 600 ppm
nPB for 6 hours/day for 5 days/week. In fact, in the ClinTrials study,
there were no consistent treatment-related changes reported in the rats
following 4, 8, or 13 weeks of exposure in any parameter evaluated in a
full functional observational battery (a suite of tests designed to
assess a full spectrum of neurotoxic effects). Because the LOAEL for
neurotoxic effects in Ichihara et al. (2000b) is actually higher than
the LOAEL identified in the two-generation study, and because the
findings on neurotoxicity from the Ichihara study conflict with the
results of the 90-day ClinTrials (1997b) study, it is erroneous to
conclude that neurotoxicity is the most sensitive endpoint for nPB
exposure.
Second, the NIOSH medical survey used by Rozman and Doull is not a
suitable basis for deriving an AEL. Use of epidemiological data for a
quantitative risk assessment requires that the exposures be well-
characterized, that the sample size be large enough to allow for the
detection of subtle effects in a statistically significant way, and
that comparisons to an unexposed control group be made. The data
provided in the NIOSH evaluation do not fit these criteria: (1) The
sample size in this study was relatively small (46 participants); (2)
the health survey was not given to an unexposed control population for
comparison; (3) no obvious exposure-response trend for headache was
seen, since the low and medium exposure groups had similar prevalence
of headache. For each of the neurological symptoms evaluated in the
NIOSH health survey, air concentrations of nPB were not statistically
different between those employees reporting the symptom compared to
those not reporting the symptom (NIOSH 2002).
Finally, EPA disagrees with Rozman and Doull's conclusion that
reproductive toxicity did not occur in workers exposed to up to 190 ppm
of nPB, which is the basis for their assertion that humans are less
sensitive to reproductive health effects of nPB compared to rats
(Rozman and Doull, 2001). The NIOSH report states that 3 workers (2
male and 1 female) who had been exposed to between 110 and 157 ppm of
nPB reported difficulty in having a child. However, as noted by the
authors of the NIOSH report, due to the small sample size and the
personal nature of the questions, there were significant limitations in
the ability of the NIOSH medical survey to detect reproductive or
fertility problems. The data from the NIOSH medical survey should not
be used to conclude that rats are more sensitive than humans to
reproductive effects of nPB, or to draw any general conclusions
regarding the potential reproductive toxicity of nPB in humans.
In the second analysis submitted by Enviro Tech, SLR International
Corporation derived an AEL for nPB of 156 ppm (SLR International,
2001b). We understand that this derivation is currently undergoing peer
review for potential publication in a scientific journal. This analysis
used benchmark dose-response modeling using data sets for several
effects taken from the various animal toxicity tests that have been
conducted with nPB. SLR derived a BMDL at a 10% response level of 156
ppm, based on reduced sperm motility in F1 males from the WIL (2001)
study. This BMDL is similar to EPA's BMDL for sperm motility of 169
ppm. SLR stated that ``Due to the relative completeness of the
toxicological database on nPB, including data on human in vitro
bioassays, use of a UF is likely not considered necessary for this
chemical.'' Thus, SLR's recommended AEL is equivalent to their BMDL.
EPA maintains that an uncertainty factor is necessary for protection of
sensitive individuals since low sperm count is a condition that can
occur in otherwise healthy workers. There are no data indicating that
human sperm are less sensitive than rat sperm. In fact, sperm
production is less efficient in humans, suggesting that human males are
likely to be more susceptible than rats to nPB (Amann, 1986). Further,
based on EPA's RfC guidelines, an uncertainty factor of 3 is necessary
to account for interspecies differences in pharmacodynamics between
rats and humans. Had SLR applied what EPA considers appropriate
uncertainty factors, their recommended AEL would have been 17 ppm.
In a memorandum submitted to Poly Systems International, Joel
Charm, a certified industrial hygienist, supported the analyses by both
SLR and Rozman and Doull. Mr. Charm suggested that establishing an
occupational exposure level of 100 ppm as a ceiling value (i.e.,
[[Page 33299]]
a level not to be exceeded during any part of the working day), coupled
with an effective Product Stewardship program, would help companies
maintain exposure to their workers as low as reasonably achievable. He
suggests that a Product Stewardship program focused on: (1) Training
material on how nPB can be handled and used safely; (2) conducting
industrial hygiene evaluations as a service to customers, to develop
actual exposure level information for a variety of end uses under
varying circumstances; and (3) monitoring the health (including
reproductive parameters) of workers would, over time, aid in assessing
the validity of the occupational exposure limit selected. He also
states that through the Product Stewardship program and the regulatory
reporting requirements of the Toxic Substances Control Act (TSCA),
Section 8, corrective actions could be taken if necessary.
While we do not agree with the AELs derived by Rozman and Doull or
by SLR, EPA agrees that producers and formulators of nPB should engage
in responsible Product Stewardship programs. Albermarle Corporation has
been conducting an extensive stewardship program for nPB involving air
sampling and workplace practice evaluation for customers to help ensure
exposures below 25 ppm. We also note that, in order to verify if
exposure levels are below a ceiling value, it would be necessary to
monitor workplace exposure continuously. Periodic evaluations of
exposure levels would be sufficient for determining long-term exposure
to workers. EPA recommends that workplace exposures should be
controlled to levels at or below the AEL in order to avoid risk of
adverse health effects.
e. Feasibility of meeting the AEL for nPB in each industrial
sector. Each of the three sectors EPA is considering in today's
proposal could potentially expose workers to nPB in different ways.
Therefore, we considered separately whether it is feasible to meet the
AEL in each of the three sectors. If EPA becomes aware of further
information showing that nPB use is likely to pose unacceptable risks
to human health in particular applications or end uses, we will find
nPB unacceptable in those applications or end uses.
Solvents cleaning. When using industrial cleaning equipment,
workers are likely to be exposed to solvent vapors continually over the
course of a workday. However, users can control nPB emissions from
vapor degreasers by changes to the equipment, as well as changes in
operating practice. For example, a user can install an additional set
of condensation coils to prevent vapor from leaving the vapor degreaser
or defluxer. An operator can tilt pieces to be cleaned to allow the
solvent to drain off inside the vapor degreaser instead of evaporating
outside of the degreaser where workers will breathe the vapors.
Exposure data on nPB used in vapor degreasers indicate that it is
possible to maintain exposure levels from 2 to 24 ppm over an 8-hour
average, as measured using personal samplers (Albemarle, 1997). In
1998, Albemarle Corporation also collected workplace monitoring data
from metal cleaning operations. Many, although not all, of the samples
collected showed concentrations that, extrapolated to an 8-hour period,
would remain under 25 ppm. In addition, another manufacturer and
distributor of nPB-based solvents stated that, ``For a properly
designed, installed, operated, and maintained traditional open-top
vapor degreaser, experience has shown that eight-hour time weighted
operator exposure levels will be < 20 ppm. For enclosed and automated
degreasers, lower exposures can be achieved'' (Amity UK Ltd, 2001).
EPA has only one set of direct exposure data for equipment that
cleans using nPB below its boiling point (``cold cleaning''). These
data are from a NIOSH Health Hazard Evaluation for a company that
produces instrumentation and components for radio and microwave
frequency communications. In this study, NIOSH measured exposures to
nPB from a cold batch cleaner that was in a special enclosed room with
a local exhaust ventilation system. The highest exposure level was 8.4
ppm (NIOSH, 2000b). However, the type of enclosure and ventilation used
at this site is not typical of most facilities using cold cleaning
equipment.
In general, it is expected that it will be more difficult to
control emissions from cold cleaning equipment than from vapor
degreasers. The design of vapor degreasers reduces emissions from the
equipment by boiling the solvent and then causing it to condense,
rather than allowing solvent vapors to be emitted. Because cold
cleaning equipment may expose workers to high levels of nPB, we
recommend that nPB not be used in cold cleaning equipment unless
additional engineering controls are instituted to keep worker exposure
to levels below the recommended AEL of 25 ppm.
The limited data available on manual cleaning indicate that it may
be difficult to attain exposures less than 50 ppm when wiping with nPB
by hand (Albemarle, 2001). The SNAP program currently does not regulate
manual cleaning with solvents. However, we recommend that nPB not be
used for manual cleaning because of the likelihood of high exposures.
Aerosol Solvents. Only limited data are available on exposure
levels to nPB from aerosol solvent usage. Four measurements on a single
user showed exposures to nPB that ranged from 5 to 14 ppm over an 8-
hour time-weighted average (Albemarle, 2001). Since the user was
cleaning brakes on public works equipment, it is possible that the
mechanic was working outdoors, or in an area that was only partially
enclosed. EPA expects that these data are not representative of the
diverse conditions under which aerosol solvents are used. Confidential
data from another facility revealed that exposures vary greatly and in
some instances can be higher than 200 ppm. In contrast to vapor
degreasers, aerosol solvents tend to be used intermittently for short
periods of 1-2 minutes. In some cases, aerosols containing nPB are used
in confined spaces without ventilation ducts and fans where workers
could be exposed to high levels over a short time. Emissions from
aerosols are typically not controlled with equipment that captures the
nPB vapor, although aerosol users can improve ventilation and reduce
exposure levels through a variety of approaches (e.g., fume hoods).
Given this information, EPA requests further workplace exposure data on
nPB's use as an aerosol solvent. In addition, we request comment on
whether nPB should be acceptable for use as an aerosol solvent, or if
its use should be limited in this end use (e.g., use limit restricting
nPB only to applications with ventilation equipment).
EPA believes that users should adhere to a short-term exposure
limit (time weighted average over 15 minutes) of three times the AEL.
We recommend this short-term exposure limit, which would equal 75 ppm
over 15 minutes, in addition to the 8-hour time weighted average of 25
ppm. We believe that limiting short-term exposure to 75 ppm in a 15
minute period of exposure is feasible with proper ventilation and/or
low use volumes. We also recommend only using aerosols containing nPB
in open or well-ventilated areas. This procedure is recommended for use
of any aerosol solvent, compared to use in enclosed, unventilated
areas.
Adhesives. In adhesives applications, exposures are expected to
vary depending upon the particular kind of application. For example, in
the foam-fabrication industry, workers generally are exposed to
evaporating solvents on
[[Page 33300]]
a long-term basis. When adhering tops on counters or tables, workers
are more likely to have breaks between exposure, with short-term
exposure being of greater concern (HSIA, 2001).
EPA is aware that it may be difficult to meet the recommended 25
ppm AEL in adhesive applications that are highly emissive. Exposure
data from nPB used in adhesives in the foam-fabrication industry show
high nPB concentrations within the workplace. At three different foam-
fabrication facilities, NIOSH investigators reported that mean
exposures to nPB ranged from 60 to 381 ppm (8-hour time weighted
averages) (NIOSH, 1999, 2000a, 2000c, 2001). In one facility, average
nPB exposures were reduced from 169 ppm to 19 ppm, following
installation of ventilation equipment recommended by NIOSH (NIOSH,
2000c). Although use of spray booths at this facility had a dramatic
effect of reducing average exposures to nPB, a significant percentage
of workers whose jobs required direct use of spray adhesive containing
nPB continued to have exposures in excess of 25 ppm. Among sprayers and
assemblers working in the Assembly area, 2 of 10 (20%) full-shift
samples exceeded 25 ppm, and among sprayers working in the Covers
department, 9 of 11 (81%) of samples exceeded 25 ppm, with a maximum of
58 ppm (time-weighted average, TWA). These findings indicate that it
may be necessary for employees to wear appropriate respiratory
protection where engineering controls do not reduce exposures to or
below the AEL. Where respirators are used to protect workers against
nPB, employers should be aware that OSHA's Respiratory Protection
standard (29 CFR 1910.134) would apply.
Because there is evidence that workplace exposures to nPB can be
reduced to levels close to or below the recommended AEL, the Agency has
concluded that it is appropriate to find the use of nPB acceptable in
adhesive applications. Nevertheless, EPA expects that businesses using
nPB in adhesive applications may have difficulty meeting the
recommended exposure limit without some form of engineering controls
such as confining operations to spray booths with ducts and a fan
providing ventilation. Further, although use of spray booths at this
facility had a dramatic effect of reducing exposures to nPB, as
discussed above, some workers whose jobs required direct use of spray
adhesive containing nPB continued to be exposed to nPB in excess of 25
ppm. Given this information, EPA requests comment on whether nPB should
be acceptable for use in adhesives.
EPA conducted a detailed risk screen for nPB use in adhesives
applications in the foam fabrication industry (ICF, 2001a , Attachment
C) since this represents the most emissive use, and the use where
workers and the general population have the highest exposures. Because
this highly emissive use passed our risk screen, we did not conduct a
formal risk screen for the solvents cleaning sector and aerosol
solvents sectors end use, because emissions and worker exposures in
these uses are expected to be lower than the adhesives end use.
2. Are There Other Entities That May Set or Recommend Workplace
Standards?
Under the National Technology Transfer and Advancement Act of 1995,
Section 12(d), Public. Law. 104-113, Federal agencies are required to
consider using technical standards that are developed or adopted by
voluntary consensus standards bodies, using such technical standards as
a means to carry out policy objectives or activities. No such standards
for occupational exposure to nPB currently exist. In comparison, the
American Conference of Governmental Industrial Hygienists (ACGIH) has
established threshold limit values (TLVs) for the primary chlorinated
solvents used in the same applications as nPB. The most current TLVs
for these solvents--25 ppm for perchloroethylene, and 50 ppm for
trichloroethylene and methylene chloride--are identical or moderately
higher than our proposed recommended guideline for nPB. It is possible
that the American Industrial Hygiene Association (AIHA) or the ACGIH
will review the toxicity of nPB in the future and set a voluntary
standard. AIHA may develop a Workplace Environmental Exposure Limit
(WEEL) for nPB. Further, in 2002, the ACGIH listed 1-Bromopropane and
2-Bromopropane (nPB and iPB, respectively) in its list of ``Chemical
substances and other issues under study.'' If either of these standard-
setting bodies recommends an exposure limit on nPB, we would make that
information available to the public for comment.
In the future, OSHA may develop a mandatory exposure limit for nPB
use in the workplace. The result of OSHA's review could result in a
permissible exposure limit (PEL) different from EPA's recommended
exposure limit of 25 ppm. Unlike nPB, the chlorinated solvents are
regulated by OSHA and have been regularly re-evaluated by OSHA, NIOSH,
and EPA (e.g., as a National Emission Standard for Hazardous Air
Pollutants). The most current permissible exposure limits for these
solvents established by OSHA are 25 ppm for methylene chloride and 100
ppm for perchloroethylene and trichloroethylene. The OSHA permissible
exposure levels for perchlorethylene and trichloroethylene of 100 ppm
were originally issued on 1971 based on the 1968 threshold limit values
established by the ACGIH. Since then, ACGIH has issued TLVs of 25 ppm
for perchloroethylene and 50 ppm for trichloroethylene and OSHA has
issued a PEL of 25 ppm for methylene chloride; as such, the Agency does
not believe that a 25 ppm recommended AEL for nPB would result in a
significant competitive advantage for any of these solvents. As stated
earlier in this preamble, EPA defers to OSHA in regulating workplace
safety. The recommended AEL in today's proposal is an interim measure
in the absence of an OSHA PEL. Thus, any PEL that OSHA sets would
supersede EPA's recommended AEL.
3. Is the General Population Exposed To Too Much nPB?
As a part of the SNAP review process for alternative chemicals, EPA
also considers exposure to the general population. Near facilities that
use nPB in non-emissive applications such as vapor degreasing, exposure
is expected to be insignificant. For emissive applications of nPB, such
as an adhesive solvent in foam fabrication, we conducted a more
detailed assessment of potential exposure to people living in the
immediate vicinity of a facility. We first estimated a community
exposure guideline, using EPA's Methods for Derivation of Reference
Concentration Guidelines (1994) as a risk index to compare against
potential community exposure. This community exposure guideline is an
estimate of a continuous inhalation exposure (averaged over 24 hours
per day, 7 days per week) to the general public (including sensitive
subgroups) that is likely to be without an appreciable risk of adverse
health effects during a lifetime. Community exposure guidelines can be
derived from a NOAEL, LOAEL, or benchmark concentration, with
uncertainty factors generally applied to reflect limitations of the
data used. Average daily exposures of people living close to facilities
where nPB is used in an emissive application were then estimated and
compared to the community exposure guideline to determine whether nPB
exposure presents an appreciable risk to the general population.
EPA derived the community exposure guideline for nPB using the same
critical
[[Page 33301]]
studies and BMDLs for spermatic effects and liver effects that were
used in developing the AEL. Adjustments were made to account for
continuous lifetime exposure and sensitive subpopulations. The lowest
BMDL of 110 ppm was based on the incidence of liver effects
(centrilobular vacuolation) in the two-generation reproductive study
(WIL, 2001). Using EPA's dosimetry guidelines for a category 3 gas (US
EPA, 1994), and making adjustments to account for continuous exposure,
the human equivalent concentration (HEC) is 110 ppm * (6 hours/24
hours) = 27.5 ppm. No adjustment for differences in pharmacokinetics
was necessary based on EPA's RfC guidelines. EPA applied an UF of 3 for
extrapolation from rat to human pharmacodynamics. An additional factor
of 10 was applied for intrahuman variability including the protection
of sensitive subpopulations (e.g., individuals with liver disease,
children, or the elderly). Therefore, the total uncertainty factor was
30 (3 for differences in pharmacodynamics, 10 for sensitive
subpopulations). The application of the uncertainty factor of 30 to the
HEC of 27.5 ppm results in a community exposure guideline of
approximately 1 ppm. EPA requests comment on the appropriate use of
uncertainty factors for the community exposure guideline.
The next lowest BMDL (169 ppm) was for the effects on sperm
motility in the second generation of male rats in the two generation
study. In the derivation of a community exposure guideline RfC for this
endpoint, EPA adjusted the BMDL to account for continuous exposure
averaged over 24 hours a day, resulting in an HEC of 42 ppm. An
uncertainty factor of up to 10 may be applied for animals to human
extrapolation in consideration of potential differences in
pharmacokinetics and pharmacodynamics. However, for the reasons listed
earlier, we did not consider an uncertainty factor necessary to account
for differences in pharmacokinetics. The results of the in vitro
studies conducted with liver cells do not allow us to draw any
conclusions regarding the relative sensitivity of the human and rat
spermatocyte to nPB. Consequently, EPA applied a factor of 3 for
differences in pharmacodynamics. Finally, an uncertainty factor of 10
was applied for intrahuman variability including the protection of
sensitive individuals in the general population (e.g., children whose
sex organs are in development, pregnant women, and individuals with low
fertility). An overall uncertainty factor of 30 results (3 for
differences in pharmacodynamics, and 10 for the protection of sensitive
individuals). The application of the overall uncertainty factor (30) to
the HEC (42 ppm) results in a community exposure guideline an RfC of
approximately 1 ppm. The estimated community exposure guideline values
are identical for both liver and reproductive effects. Consequently,
EPA estimated that a RfC community exposure guideline of 1 ppm would be
protective for all health endpoints--that is, someone exposed to an
average of 1 ppm of nPB, 24 hours of every day during a lifetime, would
not be at appreciable risk for adverse health effects during their
lifetime.
The next step was to determine whether people living close to sites
where nPB is used in emissive applications could potentially be exposed
to levels above the estimated RfC community exposure guideline of 1
ppm. Data collected from actual facilities (CCPCT, 2001) used to
characterize two scenarios: (1) A typical large, high-use adhesive
application facility where the closest resident is 100 meters away; and
(2) a smaller facility with average-use adhesive application in an
urban area, where the nearest resident is only 3 meters away.
EPA's SCREEN3 (US EPA, 1995a) air dispersion model was used to
assess the likely maximum-potential concentration of nPB from single
sources. This technique is typically used to evaluate air quality
impacts of sources pursuant to the requirements of the Clean Air Act,
such as New Source Review and air toxic regulations. The approach
applied here was the initial-phase approach used to determine if
either: (1) The source clearly poses no air quality problem or (2) the
potential for an air quality problem exists. If a potential problem
exists, then a more refined analysis is necessary.
The results from our screen indicated that modeled exposures in
either scenario did not exceed the RfC of 1 ppm. The urban scenario
where a facility uses fans to ventilate nPB horizontally (through
windows or other openings in the walls as opposed to openings in the
roof), modeled exposures of 0.24 ppm at a distance of 3 meters away
from the source, 0.19 ppm at 5 meters from the source, and 0.13 ppm at
10 meters from the source. These levels were by far the highest
concentrations of nPB exposures modeled. The majority of modeled
exposures were at least an order of magnitude lower, and ranged from 0
ppm to 0.08 ppm. Because the community exposure guideline was not
exceeded for any of the exposure scenarios in this conservative
screening approach, EPA has concluded that nPB exposure to populations
living close to adhesive application sites is not a major concern. A
memo describing the risk screen in detail may be found in the public
docket (ICF, 2002a).
4. What Limit Is EPA Proposing on Isopropyl Bromide Contamination of
nPB as a Condition of Acceptability, and Why?
Isopropyl bromide (iPB or 2-bromopropane), an isomer of nPB (1-
bromopropane), is a contaminant that is created to different degrees in
the manufacture of some nPB formulations. In reviewing the
toxicological risks of iPB, EPA initially was concerned that its
molecular structure was similar to chemicals that are potent
reproductive toxins and carcinogens. This concern focused on the
position of the halogen atom within the compound. There are
toxicological data that indicate that when the halogen atom is located
on the second carbon, there may be increased potential for the compound
to cause cancer when compared to the compound with the halogen atom on
carbon number 1. One example of this is the differential toxicity of 1-
nitropropane and 2-nitropropane. Inhalation exposure to 2-nitropropane
has been linked to liver toxicity in humans and has resulted in liver,
and to a lesser extent, lung toxicity in male and female Sprague-Dawley
rats (US EPA, 1991); it has also been shown to induce liver cancer in
both Sprague-Dawley (IARC, 1992) and Fischer rats (Fiala, 1995). 1-
Nitropropane has shown no carcinogenic potential to date.
Direct data on the carcinogenic potential of iPB are limited,
although it has been shown to induce reverse mutations in bacteria
(Maeng and Yu, 1997). Further, iPB was shown to be more cytotoxic and
genotoxic to human liver cells than nPB and other toxins, including
methylene chloride and trichloroethylene (SLR, 2001a). The combination
of the position of the bromine atom in iPB (and its relationship to the
carcinogenic potential of the compound) and the genotoxicity of the
compound in bacterial and human cells indicate that caution is
necessary when recommending an acceptable exposure concentration for
iPB.
In the limited animal testing data available, iPB has been shown to
be inherently more toxic than nPB on reproductive and hematopoietic
endpoints. In two separate studies, significant disruptions in the
estrous cycles and abnormal growth in uterine cells were reported in
female rats
[[Page 33302]]
exposed to iPB daily for 9 weeks (Kamijima, 1997a, 1997b; Yu, 2001).
Daily exposure of male rats to iPB at 300, 1000, and 3000 ppm was
associated with effects ranging from reduced body and organ (e.g.,
kidneys, liver, testis) weight, reduced sperm counts and sperm
motility, abnormal sperm, reduced red blood cell and platelet counts,
and hemoglobin volume (Ichihara, 1997). A recent study has been
published (Sekiguchi, 2002) in which the effects of iPB exposure on the
reproductive physiology of female F344 rats were investigated. The rats
were exposed to air (in the control group, the number of animals, n, is
7) or 50 (n=6), 200 (n=7), or 1000 (n=9) ppm of iPB via whole-body
inhalation for 8 hours/day for 21-24 days (exact number of days not
specified in the article). A larger number of females at the high
concentration exhibited an estrous cycle of 6 days (7 of 9
animals) than those at the control, low- and mid-concentration (4, 2,
and 3, respectively) which corresponded to the greater number of
estrous cycles lasting 6 days (9 of 34 animals) in the high-
concentration group as compared to the other groups (4 of 31, 4 of 30,
3 of 30). A dose-dependent increase in the number of days/cycle was
observed in rats at 200 and 1000 ppm. These increases did not reach
statistical significance, however. A smaller number of females per
group was analyzed for uterine and ovary weights because only rats
showing the estrous stage upon vaginal smear test were chosen for
autopsy (5, 5, 5, and 7, respectively in the low-, mid-, and high-
concentration groups). No changes were noted in the weights of ovaries
or uterus, or in the number of ovulated ova among any of the female
groups (exposed or controls). Although this study indicates that iPB
was not a strong reproductive toxin in the female rat, the small number
of animals exposed is a significant limitation to the study. The dose
dependent increase in estrous cycles observed at 200 and 1000 ppm
suggest the potential for reproductive failure from exposure to this
compound. These results also indicate the need for additional studies
using greater numbers of exposed animals.
Both male and female workers occupationally exposed to iPB have
been found to exhibit some of the same effects reported in animal
toxicological studies. Ichihara (1999) reported low sperm motility, low
semen volume, abnormal sperm cells, and decreased blood cell count,
hemoglobin and hematocrit in otherwise healthy Chinese male workers
exposed to a wide range of iPB concentrations (2.5-111 ppm). Abnormal
or an absence of menstruation was associated with iPB exposure in
several female workers, as well as reduced blood cell count,
hemoglobin, and hematocrit. Employees of an electronics factory in
South Korea showed similar effects following exposure to iPB (Kim,
1996). In female workers, disrupted or absent menstruation, abnormal
hormone levels, hot flashes, and abnormal bone marrow were found, while
male workers exhibited significantly reduced sperm counts and sperm
motility.
CERHR convened an Expert Panel to consider existing toxicological
studies on effects of both nPB and iPB. (See section IV.A.1.c. for a
discussion of CERHR review process and the Expert Panel Report.) The
CERHR Expert Panel came to the following conclusions on the existing
studies on iPB (CERHR, 2002b, p. 44):
[sbull] Available human and animal data are insufficient to draw
conclusions on the potential for developmental toxicity due to iPB.
[sbull] There is sufficient evidence that iPB is a reproductive
hazard in men and women, particularly based upon the epidemiological
data from Korea.
[sbull] At low levels (less than 0.004 ppm), there is minimal
concern for human reproduction. At higher levels up to 1.35 ppm, there
is some concern.
[sbull] For reproductive data from male rats, the panel identified
a NOAEL of 100 ppm.
The toxicological studies on male reproductive endpoints for iPB
have limitations which (e.g., small number of dose groups) make them
inappropriate for use in quantitative risk assessment. Although the
occupational exposure studies also are limited, given the mutagenicity
of the compound and that human exposures have resulted in significant
health effects consistent with those reported in the available animal
studies, the Agency considers it appropriate to limit the amount of iPB
exposure resulting from nPB use to the maximum extent feasible.
Today's action proposes to limit SNAP acceptability of nPB to those
formulations of nPB that contain concentrations less than 0.05% iPB by
weight before adding stabilizers or other chemicals. The current
American Society for Testing and Materials (ASTM) standard for vapor
degreasing grade and general grade nPB specifies that unstabilized nPB
must have less than 0.1% of iPB as a contaminant. EPA believes that
this level should be reduced to 0.05% given the toxicity of iPB, and
the fact that achieving a level of 0.05% is technologically feasible
and would not cause significant economic impacts (US EPA, 2003). The
Agency also requests comment on the appropriateness of alternative
concentration limits for iPB in nPB, including 0.1%. If this provision
is finalized, the iPB concentration limit would be a condition that all
users in the U.S. must observe in all sectors and end uses where nPB is
listed as acceptable.
In order to show compliance with the use condition, end users would
need to keep records to demonstrate that the nPB used in the product
contains no more than 0.05% iPB by weight before adding stabilizers or
other chemicals. Documentation could involve, for example, keeping a
certificate of analysis or purity provided by the manufacturer or
formulator for two years from the date of creation of that record. Such
records are customary business information that chemical companies
provide to their customers, so we do not expect that this requirement
will impose an additional paperwork burden.
B. Ozone Depletion Potential
The ozone depletion potential (ODP) of a chemical compound provides
a measure of its impact on stratospheric ozone levels relative to the
impact of an equal mass emission of CFC-11. The Parties to the Montreal
Protocol have used the ODP benchmark index as a means of characterizing
the relative risks associated with the various ozone-depleting
compounds subject to the requirements of the Protocol and to calculate
the total allowable production and consumption of different classes of
ozone depleting substances. Every four years the World Meteorological
Organization publishes the Scientific Assessment of Ozone Depletion.
These assessments are authored by leading experts in the fields of
atmospheric science and atmospheric chemistry, and include the most
current research findings relevant to the science of ozone depletion.
These assessments, along with other studies in the field of atmospheric
chemistry, have traditionally focused on compounds with relatively long
atmospheric lifetimes (in excess of 3 months).
Two-dimensional (2-D) models that base calculations on latitude and
altitude are sufficient for calculating the ODP of long-lived
chemicals. However, 2-D models cannot simulate the complex atmospheric
transport pathways that are necessary to determine the ODP of short-
lived compounds like nPB (Wuebbles, 2000). nPB is estimated to remain
in the atmosphere for only 11 to 20 days after
[[Page 33303]]
emission.\12\ The short lifetime of nPB complicates the calculation of
its ODP because it is not valid to make the standard simplifying
assumption that concentrations are ``well mixed'' in the troposphere.
Thus, a meaningful comparison can be made between the ODP of nPB and
the longer-lived compounds already controlled under the Montreal
Protocol only by using the results from a 3-D model that bases
calculations on longitude, latitude, and altitude to augment the ODP
calculation using a 2-D model.
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\12\ Wuebbles et al., 1998; Wuebbles et al., 2000.
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Generally, a compound emitted in the troposphere travels toward the
equator and into the tropics before rising convectively into the
stratosphere. As a result, a compound emitted at high latitudes, such
as the northern United States or the southern tip of Brazil, will take
longer to reach the stratosphere than one emitted in the tropics. For a
long-lived chemical, this difference in travel time is insignificant.
But for a short-lived compound such as nPB, which is subject to
degradation in the troposphere, the latitude of emission can have a
significant impact on the amount of ozone-destroying bromine that is
delivered to the stratosphere.
Using a combination of 2-D and 3-D models, Wuebbles et al. (2001)
estimated the ODP to be between 0.016 and 0.019 for nPB emissions over
the United States. In the tropical latitudes, over India, Southeast
Asia and Indonesia, nPB emissions have a larger ODP of 0.087 to 0.105.
A more recent paper by Wuebbles found that the ODP of nPB emissions
from the United States would be closer to 0.013-0.018, while nPB
emissions in the tropics would have an ODP of 0.071 to 0.100 (Wuebbles,
2002).
In proposing to list nPB as an acceptable substitute for CFC-113,
methyl chloroform and HCFC-141b, EPA has considered that the ODP for
nPB at the latitude of the continental U.S. is substantially less than
the ODPs for the chemicals it would replace (0.8 for CFC-113, 0.1 for
methyl chloroform, and 0.11 for HCFC-141b). Given that fact, we do not
believe that nPB's ODP is a compelling reason to list it as an
unacceptable substitute for CFC-113, methyl chloroform, and HCFC-141b
for use in the U.S.
While advances in modeling are producing more specific methods to
better estimate nPB's ODP, the value will never be pinpointed to a
single number that may be applied to all latitudes. EPA notes that if
the ODP were as high in the U.S. as it is in the tropics (0.071 to
0.100), we would have found it unacceptable as a substitute. When
making regulatory determinations, governments or users in other
latitudes should consider the ODP at their latitude as well as the
toxicity of other solvents available for use. For example, users in
other counties may find nPB preferable to carbon tetrachloride, which
has a high ODP (1.1) and is highly toxic. On the other hand, users in
the tropics should realize that nPB at their latitude has an ODP
comparable to substances controlled by the Montreal Protocol (methyl
chloroform or HCFC-141b). EPA also recommends that any decisions on the
use of nPB outside the U.S. should be based on latitude-specific ODPs
and volumes of the chemical projected to be used in those regions.
Few commenters on the ANPRM discussed the ODP of nPB. However, the
Agency agrees with two commenters who stated that nPB's low ODP should
be balanced against the much longer atmospheric lifetime of other
choices.
We have attempted to gather and assess all available information
from the full range of experts on nPB's ODP. EPA continues to be
interested in receiving from the public any other information
pertaining to the atmospheric effects and ODP of short-lived
atmospheric chemicals, especially nPB. In the event that data become
available after final rulemaking that are contrary to the current
scientific understanding, section 612 of the CAA allows the Agency to
reconsider our decision under the SNAP program.
C. Global Warming Potential
The global warming potential (GWP) index is a means of quantifying
the potential integrated climate forcing of various greenhouse gases
relative to carbon dioxide. Thus, the GWP of carbon dioxide is, by
definition, equal to one. Since GWP is a measure of the climate forcing
integrated over time, the value of the index depends on the choice of
time horizon. The standard GWP used for making climate-related policy
decisions is based on a 100-year time horizon (called the 100yr
GWP).\13\
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\13\ The 100yr GWP is the index recommended by the
Intergovernmental Panel on Climate Change (IPCC) for comparing the
climate impacts of various global warming gases. The United States
employs the standard 100yr GWP index for making climate policy
decisions and reporting of greenhouse gases.
---------------------------------------------------------------------------
The 100yr GWP of nPB is 0.31 (Atmospheric and Environmental
Research, Inc., 1995). This is a relatively low GWP, representing a
climate forcing approximately one third that of carbon dioxide, by
weight. Estimations of the net climate impact must take into
consideration the amount of the compound expected to be emitted. As
will be discussed in section V.B. below, nPB will most likely be
emitted in small enough quantities worldwide that there should not be a
concern about its causing climate change. Additionally, the GWP of nPB
is considerably lower than that of the chemicals it potentially
replaces. (100yr GWP values are 6000 for CFC-113, 140 for methyl
chloroform and 700 for HCFC-141b.) \14\ Therefore, we conclude that the
use of nPB as a substitute for CFC-113, HCFC-141b, or methyl chloroform
should not be restricted based on its GWP.
---------------------------------------------------------------------------
\14\ All GWPs (other than that of nPB) discussed in this NPRM
are taken from the Scientific Assessment of Ozone Depletion: 1998
(WMO, 1999).
---------------------------------------------------------------------------
D. Flammability
nPB forms flammable mixtures in air within only a narrow range. All
estimates that EPA reviewed fall somewhere within the range of 3.5%-9%.
Most, but not all, of the material safety data sheets we reviewed state
that nPB has no flashpoint. The 1998 Report of the United Nations
Environment Programme's Solvents, Coatings and Adhesives Technical
Option Committee stated that ``under certain test conditions, using
standard flash point testing apparatus, pure nPB has demonstrated a
flash point at -10[deg]C * * * [O]ther ASTM test methods have resulted
in no observed flash point'' (UNEP, 1999). In response to information
requests in the nPB ANPRM, various commenters asserted that nPB has a
flashpoint of 10[deg]C, 14[deg]C, and 21[deg]C-25[deg]C, 70[deg]F
(21[deg]C), and 70[deg]C. These data are inconclusive about the
flashpoint of nPB and whether nPB is likely to be flammable under
normal use conditions.
In addition, we are aware that many manufacturers of foam cushions
use adhesives containing nPB because it is essentially non-flammable
compared to many other solvents used in adhesives, such as acetone or
heptane. Also, one company has submitted a fire suppressant containing
nPB as the active ingredient for review by the SNAP program. (We are
not addressing this incomplete submission in today's proposed rule.) It
is not surprising that nPB would have little or no flammability, given
that many organic compounds containing bromine have little or no
flammability, such as halons or hydrobromofluorocarbons.
Based on the full range of available information, we do not
currently believe that the use of nPB as a substitute for CFC-113,
methyl chloroform, or HCFC-141b should be restricted because of
flammability. EPA, however, invites
[[Page 33304]]
commenters to submit more specific information concerning the
flashpoint of pure nPB. We are aware that nPB blends may have
flashpoint characteristics different from that of pure nPB, depending
on the nature of the additives or stabilizers. In this rulemaking, EPA
is evaluating only pure nPB as a substitute for CFC-113 and methyl
chloroform. We therefore are not interested in receiving information
concerning the flashpoints of blends that contain nPB. Commenters
providing information on nPB's flashpoint should refer to the specific
test methodology and apparatus used to determine the flashpoint, such
as ISO 1523, American Society of Testing Materials (ASTM) E-681, D92,
D93-85--Pensky-Martens closed cup, or D56-96--Tag closed cup. EPA also
invites readers to submit information concerning any potential fire or
explosion hazards that may result from the use in solvent cleaning of
compounds that have flashpoints within the range of normal atmospheric
pressures and temperatures.
E. Other Environmental Concerns
Because nPB breaks down in the atmosphere within 21 days, and is
not particularly soluble in water, it is unlikely that ``rain out''
from nPB released into the atmosphere could cause contamination of
water supplies. However, as with all chemicals, significant
contamination of soil and water can result when directly introduced
into water or onto the ground. Thus, EPA expects that users will
dispose of nPB in accordance with relevant regulations under the
Resource Conservation and Recovery Act, and with applicable state and
local regulations. Compliance with these regulations will mitigate the
possibility that nPB might enter water supplies or top soil.
nPB is a volatile organic compound (VOC). VOCs are associated with
the formation of ground-level ozone, a respiratory irritant. Therefore,
nPB use currently is controlled under state and local regulations
implementing Federal clean air requirements at 40 CFR part 51. These
regulations are intended to bring areas into compliance with the
National Ambient Air Quality Standards for ground-level ozone. Users
located in ozone non-attainment areas may need to consider using other
alternatives for cleaning that are not VOCs or control emissions.
F. Comparison of nPB to Other Solvents
Section 612 of the Clean Air Act directs EPA to determine the
acceptability of a replacement substance (``substitutes'') for class I
and class II ozone depleting substances based on whether such
substitute creates an overall greater risk to human health and the
environment than other substitutes that are available. Section 612(c)
specifically states that the Administrator shall issue regulations:
providing that it shall be unlawful to replace any class I or
class II substance with any substitute substance which the
Administrator determines may present adverse effects to human health
or the environment, where the Administrator has identified an
alternative to such replacement that--
(1) reduces the overall risk to human health and the
environment; and
(2) is currently or potentially available.
Thus, EPA must compare the risks to human health and the
environment of a substitute to the risks associated with other
substitutes that are currently or potentially available. In addition,
EPA also considers whether the substitute for class I and class II ODSs
``reduces the overall risk to human health and the environment''
compared to the ODSs being replaced, consistent with the safe
alternatives policy of Sec. 612.
In our evaluation, we considered the substitutes available within a
given end use. In other words, we compared nPB as a metal cleaning
solvent against other metal cleaning alternatives, and we compared nPB
as a carrier solvent in adhesives to other adhesive alternatives.
Because of the large amount of overlap in the alternatives available in
the different end uses, the discussion below will mention alternatives
from multiple end uses where nPB is used.
Although EPA does not judge the effectiveness of alternatives, this
factor is an additional one that we consider when determining what
alternatives are available in a particular application within an end
use. For example, aqueous cleaners are the substitute of choice for
many in the metal cleaning end use and many electronics applications
now use the ``no clean'' technology. However, some types of soils are
especially difficult to remove and some applications require a high
degree of cleanliness; thus, in some applications, particularly in
precision cleaning, there may still be a need for organic solvents for
cleaning. Depending on the particular application, it may be necessary
to use an aggressive cleaning solvent such as nPB.
nPB has an ODP of 0.013 to 0.018 at the latitudes of the
continental U.S. Thus, nPB reduces risk compared to CFC-113, methyl
chloroform, and HCFC-141b, the ODSs it replaces, which have ODPs of
0.8, 0.1, and 0.11, respectively. HCFC-225ca/cb has an ODP of
approximately 0.03. HCFC-225ca/cb is acceptable in metals cleaning and
aerosol solvents, and acceptable subject to use conditions in precision
cleaning and electronics cleaning. Although HCFC-141b has been phased
out of production in the U.S., its use is currently acceptable in
aerosol solvents; HCFC-141b has a higher ODP than nPB. HCFC-123 has an
ODP of 0.0124, which is comparable to that of nPB. HCFC-123 is
acceptable in precision cleaning. There are other acceptable cleaners
that essentially have no ODP (aqueous cleaners, hydrofluoroethers
(HFEs), hydrofluorocarbon (HFC)-4310mee, HFC-365mfc, HFC-245fa,
hydrocarbons, volatile methyl siloxanes (VMSs), methylene chloride,
trichloroethylene (TCE), perchloroethylene (PERC), and
parachlorobenzotrifluoride (PCBTF).
nPB has a GWP of only 0.31, which is lower than or comparable to
that of the lowest GWP solvents. Acceptable HCFC, HFC and HFE solvents
all have GWPs that are two to four orders of magnitude higher than that
of nPB (55 to 1700 on a 100 year time horizon compared to
CO2).
nPB is a volatile organic compound for purposes of EPA regulations,
although there are petitions with EPA requesting its exemption. Thus,
nPB currently is subject to regulations for ground-level ozone and
local air quality. nPB is not currently regulated as a hazardous air
pollutant and is not listed as a hazardous waste under RCRA.
nPB is less flammable than many acceptable substitutes, such as
ketones, alcohols, terpenes, and hydrocarbons. nPB is comparable in its
low flammability to chlorinated solvents, HCFCs, HFEs, HFC-245fa, HFC-
4310mee, and aqueous cleaners.
EPA used an acceptable exposure limit of 25 ppm as the basis for
comparison with measured exposure levels in the workplace to determine
whether nPB could be used safely, and thus, to determine the
acceptability of nPB. EPA found that nPB could be used as safely at 25
ppm as other acceptable solvents when they are used at their AELs or
other relevant occupational exposure limits, such as OSHA PELs or ACGIH
TLVs.\15\ Based on the
[[Page 33305]]
assumption that most users will attain exposure levels at or below the
AEL of 25 ppm, EPA finds nPB acceptable in terms of its human health
risks. As discussed in section IV.A.4, ``What limit is EPA proposing on
isopropyl bromide contamination of nPB as a condition of acceptability,
and why?'' iPB is a contaminant in nPB formulations that is
considerably more toxic than nPB. Therefore, in order for nPB
formulations to ``reduce overall risk to human health and the
environment,'' EPA finds it necessary for users to use nPB formulations
that have minimal levels of iPB. Hence, the Agency's proposed decision
of acceptability depends on the condition that users use nPB
formulations that limit the amount of iPB. EPA's proposes that this
limit be 0.05% before other chemicals are added.
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\15\ The recommended AEL for nPB is lower than that for many
acceptable solvents (HFEs, ketones, HFCs, HCFC-225ca/cb,
hydrocarbons), but is higher or comparable to the AEL for some
acceptable solvents (d-limonene, VMSs, dichlorobenzotrifluoride,
HCFC-123, methylene chloride, PCBTF). However, a direct comparison
between two compounds with different AELs does not necessarily mean
that using a compound with a higher AEL is more risky. Actual
exposure levels will vary based upon factors other than the AEL,
such as emission controls in place, work practices, ventilation,
rate of spraying, and vapor pressure of the solvent.
---------------------------------------------------------------------------
Balancing these different factors, it is not clear that nPB poses
greater risks than other substitutes in the same end uses, so long as
nPB is used consistent with the use condition and recommended AEL.
Further, it appears that nPB reduces overall risk compared to the ozone
depleting substances being replaced. Thus, EPA proposes to find that
nPB is acceptable, subject to a use condition.
V. What Other Factors Did EPA Consider That Are Unique to nPB?
A. Review of nPB by Other Federal and International Programs
In proposing to find nPB acceptable in solvents cleaning, and as a
solvent in adhesive and aerosol applications, we have sought to avoid
overlap with other existing regulatory authorities. EPA's mandate under
the CAA is to list agents that ``reduce overall risk to human health
and the environment'' for ``specific uses.'' In light of this
authorization, EPA is recommending an occupational exposure limit
which, if adhered to, would result in the safe use of nPB in the
workplace. This is an interim measure until OSHA issues a PEL for nPB.
EPA defers to OSHA on workplace safety standards, and is not in any way
assuming that agency's responsibility for regulating workplace safety.
As stated in a footnote in today's proposed rule language at the
end of this document, ``In accordance with the limitations provided in
section 310(a) of the Clean Air Act (42 U.S.C. 7610(a)), nothing in
this [rule] shall affect the Occupational Safety and Health
Administration's authority to enforce standards and other requirements
under the Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et
seq.).'' EPA's recommended workplace exposure guidelines, which are not
regulatory, and use requirements, which are not expressly related to
use in the workplace, will not bar OSHA from regulating under authority
of the Occupational Safety and Health Act.
As mentioned above in section IV.E, nPB is a VOC. Two companies
have petitioned EPA to exempt nPB from VOC regulations. To date, EPA
has not received sufficient information on photochemical reactivity of
nPB and thus, has no plans to exempt it. In contrast to other solvents,
nPB is not controlled as a hazardous air pollutant under the CAA and
generates wastes that are not considered hazardous under regulations
implementing the Resource, Conservation and Recovery Act (RCRA).
Several commenters on the ANPRM argued that because no U.S.
environmental authorities regulate nPB use, EPA's SNAP program has all
the more obligation to establish an acceptable exposure limit for the
workplace, even if it is recommended rather than mandated (IRTA, 1999).
With today's proposed rule, EPA is recommending a workplace exposure
limit to protect workers exposed to nPB in the absence of OSHA
regulations.
While the Montreal Protocol currently does not control the
production and distribution of nPB worldwide, nPB may be controlled by
the Protocol in the future. At the Thirteenth Meeting of the Parties to
the Montreal Protocol in Colombo, Sri Lanka, the Parties made a
decision regarding nPB. Decision XIII/7 states:
Noting the Technology and Economic Assessment Panel's report
that n-propyl bromide (nPB) is being marketed aggressively and that
nPB use and emissions in 2010 currently projected to be around
40,000 metric tonnes,
A. To request Parties to inform industry and users about the
concerns surrounding the use and emissions of nPB and the potential
threat that these might pose to the ozone layer;
B. To request Parties to urge industry and users to consider
limiting the use of nPB to applications where more economically
feasible and environmentally friendly alternatives are not
available, and to urge them also to take care to minimize exposure
and emissions during use and disposal;
C. To request the Technology and Economic Assessment Panel to
report annually on nPB use and emissions.
B. Potential Market for nPB
There are varying estimates of the total market for nPB. The
Brominated Solvents Consortium, which consists of producers of nPB,
estimated in 2001 that approximately 9.2 million pounds of nPB were
sold worldwide in 2000, with that number expected to rise to 15 million
pounds in 2002 (Biles, 2001). In contrast, the Technology and Economic
Assessment Panel (TEAP) of the United Nations Environment Programme
(UNEP) estimated that the ``most likely'' amount of nPB use in 2010
would be between 44 million and 132 million pounds worldwide, pending
the result of toxicity testing and price trends of various solvents
(UNEP, 2001). EPA believes that the actual market size in 2010 may be
lower than the 44-132 million pounds cited by the TEAP report. Further,
since the TEAP report was published, some manufacturers and blenders of
nPB have withdrawn their products from the market.
EPA notes that the TEAP report based its estimates of how much nPB
would be used by assuming that nPB will displace significant amounts of
chlorinated solvents and HCFCs in the marketplace. The report states,
``If occupational exposure limits for nPB were 2-4 times higher than
exposure limits of methylene chloride, nPB would replace a substantial
portion of methylene chloride solvent use even if nPB had a
significantly higher price. High rates of market penetration will
require U.S. EPA SNAP listing, a favorable AEL, and market confidence''
(UNEP, 2001). Given that today's proposal recommends an AEL equivalent
to that for methylene chloride (OSHA PEL) and perchloroethylene (ACGIH
TLV) and slightly lower than that for trichloroethylene (ACGIH TLV = 50
ppm, 8 hour TWA), it is likely that the TEAP's estimates for market
penetration of nPB are too high.
In addition, we note that producers of HCFC-141b, a solvent with
slightly lower cost and similar solvency to nPB, never sold more than
36 million pounds per year as a solvent, even at the height of its
usage (AFEAS, 2002). HCFC-141b has recently been phased out of
production in the U.S. and the Agency expects nPB to be only one of
several alternative solvents that will substitute for it. Further,
experience with the growth of the market for HCFC-141b suggests that
the growth in the market for nPB is unlikely to continue at its current
pace for more than a few years. The most recent information from
suppliers of nPB indicates that in 2001, sales were approximately 9
million pounds, similar to the level in 2000 (Biles, 2002).
[[Page 33306]]
C. Estimated Economic Impacts on Businesses
As part of our rulemaking process, EPA estimated potential economic
impacts of today's proposed regulation. In our analysis, we assumed
that capital costs are annualized over 10 years and that the discount
rate for determining net present value is 7.0%. We found the following
impacts from the regulatory use condition on the iPB content in nPB
formulations:
[sbull] In general, users in the solvent cleaning sector and
aerosol solvent end use are already using nPB formulations containing
less than 0.05% iPB by weight, and will experience little or no rise in
prices. Most of the costs of compliance would fall upon adhesives
users, since some of them currently use nPB formulations containing as
much as 1% iPB.
[sbull] If today's proposed rule were to become final, the cost of
the regulatory condition to the user community would be in the range of
$2 to $3 million per year.
EPA also considered potential costs end users could incur if they
implemented the recommended acceptable exposure limit. Qualitatively,
EPA found that those users using nPB-based solvents in a vapor
degreaser would save money by reducing solvent losses, and that the
savings would recover the costs of emissions controls (e.g., secondary
cooling coils, automated lifts or hoists) within a year of
installation. Based on evidence from solvent suppliers, EPA believes
that some of those users would have chosen to use nPB in order to avoid
meeting requirements of the national emission standard for halogenated
solvents cleaning and that they would only become aware of the
potential savings due to reduced solvent usage as a result of today's
proposal (Ultronix, 2001; Albemarle, 2003). Based on the experience of
companies that assist their customers in meeting an exposure limit of
25 ppm for nPB, we assumed that 75% to 90% of nPB users in the non-
aerosol solvent cleaning sector already have exposure levels of 25 ppm
or less. Of those nPB users with exposure levels above 25 ppm, we
examined the cost associated with reducing emissions by 50% to 75%. EPA
also found:
[sbull] Balancing the savings due to reduced solvent loss and the
cost of emission controls on vapor degreaser, the range of costs for
solvent cleaning ranged from a net savings of $83,900 to a cost of
$2000 per user.
[sbull] Installing ventilation equipment was a minor expense for
aerosol solvent users ($124 to $1230 annualized cost per user).
[sbull] The more extensive ventilation equipment necessary for
adhesive users was more expensive ($24,000 to $39,000 annualized cost
per user).
[sbull] EPA estimated that full implementation of the recommended
workplace exposure guideline across all nPB users in all three
industrial sectors would range in cost from a potential net savings up
to $1.9 million to a cost of $5.5 million dollars per year. The value
will depend on the number of users that attempt to meet the recommended
exposure guideline, the initial exposure level of cleaning solvent
users, the price of nPB, and the amount of emission control equipment
or ventilation equipment installed. The high end of the range likely
would be an overestimate of actual impacts because, among other things,
it does not consider that some users may choose to switch to other
alternatives.
[sbull] When the potential costs of compliance with the regulatory
use condition and implementation of the recommended acceptable exposure
limit are considered together, EPA found the total cost to range from a
savings of $0.1 million to a cost of $8.1 million.
For purposes of comparison with these costs numbers, average values
of shipments as a proxy for revenues for different types of businesses
are as follows:
Table 3.--Examples of nPB Users by NAICS Code or Subsector and Average Annual Value of Shipments
----------------------------------------------------------------------------------------------------------------
Average annual
value of
shipments by each
NAICS code for subsector code NAICS description Example Uses of nPB company in
subsector
(million)
----------------------------------------------------------------------------------------------------------------
326150.......................... Urethane and other foam Carrier solvent in adhesivs to 10.1
product (except stick together foam pieces in
polystyrene) foam fabrication.
manufacturing.
332............................. Fabricated Metal Product Metals cleaning to remove oil, 3.9
Manufacturing. grease, and wax from metal parts.
333............................. Machinery Manufacturing. Metals cleaning to remove oil, 8.9
grease, and wax from metal parts.
334............................. Computer and Electronic Electronics cleaning, and aerosol 25.2
Product Manufacturing. solvent use to remove solder
flux from circuit boards.
336............................. Transportation Equipment Aerosol solvent use for cleaning 44.6
Manufacturing. aerospace equipment; carrier
solvent in adhesives for
aircraft seating.
337............................. Furniture and Related Carrier solvent in adhesives for 3.1
Product Manufacturing. cushions or kitchen countertops;
metals cleaning to remove grease
from metal furniture parts.
----------------------------------------------------------------------------------------------------------------
For more detailed information, see section X.C. below and EPA's
analysis in the docket (US EPA, 2003).
VI. How is EPA Responding to Comments on the Advance Notice of Proposed
Rulemaking (ANPRM) and December 18, 2000 Notice of Data Availability?
EPA received 66 comments on the February 18, 1999, Advance Notice
of Proposed Rulemaking (64 FR 8043) from 61 commenters. Forty-eight
commenters advocated listing nPB as an acceptable substitute for CFC-
113 and methyl chloroform under SNAP; ten commenters opposed listing
nPB as acceptable; and three commenters responded to the information
requests contained in the ANPRM without taking a position on the
acceptability of nPB. Close to one-third of the commenters were
manufacturers of products that require solvent cleaning. Other
commenters included chemical manufacturers, solvent and lubricant
distributors, consultants, academicians, adhesive manufacturers,
product repair companies, vapor degreaser manufacturers, an aerosol
manufacturer, an adhesive distributor, a machinery distributor, the
U.S. Army, the U.S. Department of Energy, a solvent
[[Page 33307]]
blender, a printed circuit board repair facility, and a labor union.
Almost all of the comments focused on the use of nPB in solvent
cleaning, although the Agency did receive a few comments on the use of
nPB in adhesives and aerosols applications. No commenter suggested
using nPB in coatings or inks.
Many of the commenters described the complex task of searching for
an optimal substitute for CFC-113 or methyl chloroform. Factors they
have considered include maintaining superior performance, minimizing
contamination, maintaining cost-effective and efficient processes,
complying with local and other national regulatory requirements,
assuring employee safety, and meeting exacting customer standards.
These commenters often described their specific experiences using nPB,
and compared nPB with other solvents and with other cleaning processes
such as aqueous cleaning. Proponents of nPB listed as its chief
advantages its lower cost compared to some alternatives (e.g., HFCs,
HFEs), lack of corrosiveness, potency as a solvent, low conductivity,
minimal residues, and quick drying time. They also noted its ODP, short
atmospheric lifetime and low GWP.
One commenter stated that because of its expense, users may use nPB
more efficiently than they would use other, less expensive solvents.
The commenter, a manufacturer of precision electromagnetic relays,
formerly used about 5,000 pounds of methyl chloroform each year, and
now uses about 1,500 pounds of nPB. Another commenter noted that nPB's
bad odor provides users with an incentive to minimize evaporative
losses. Commenters who oppose listing nPB as an acceptable substitute
cited its instability, reactivity, and toxicity. Several commenters
argued that nPB should not be used in solvent cleaning because it is
largely uncontrolled and relatively little is known about its health
effects.
In response to the Agency's December 18, 2000, SNAP notice and
update on nPB (65 FR 78977), one commenter expressed concern about the
use of nPB in cleaning and adhesive applications because of data
showing that nPB is a reproductive toxin. The commenter also noted that
the chemical sold as nPB contains fairly high quantities of iPB, a
potent reproductive toxin. In addition, the commenter expressed concern
that one manufacturer of nPB had recently left the market, and asked
EPA to seek input on setting the proper exposure level from NIOSH,
OSHA, and toxicologists who are not from industry or EPA.
Our proposal today reflects the Agency's agreement with those
commenters who stated that there are some cleaning operations for which
only nPB (and presumably, the CFC-113 or methyl chloroform that it
replaced) meets all of the criteria necessary for the success of those
operations. However, we also agree that some, but not all, cleaning
operations that formerly relied on CFC-113 or methyl chloroform can use
alternative cleaning agents, or alternative processes such as aqueous
or semi-aqueous cleaning. EPA has discussed the results of the 2-
generation reproductive study (WIL, 2001) and the recommended exposure
limit with NIOSH as well as outside toxicologists not involved with the
solvent industry or EPA, as one commenter suggested. We agree that the
quantity of iPB in nPB is of concern. In response, we are proposing
today to limit the iPB content in nPB to 0.05% by weight. We also are
recommending an acceptable exposure limit for nPB of 25 ppm as an
eight-hour time-weighted average, and recommending that users employ
controls to minimize worker exposure to nPB to the lowest levels
reasonably possible. The Agency believes that today's proposed rule
takes into account environmental and workplace safety concerns
associated with nPB, and that adhering to the recommended AEL of 25 ppm
will protect against adverse health effects.
VII. What Should I Include in My Comments on EPA's Proposal?
In your comments, please explain what you think EPA should do in
this rulemaking and why you think your suggested approach is
appropriate. You may find the following suggestions helpful for
preparing your comments:
1. Explain your views as clearly as possible.
2. Describe any assumptions that you used.
3. Provide any technical information and/or data you used that
support your views.
4. If you estimate potential burden or costs, explain how you
arrived at your estimate.
5. Provide specific examples to illustrate your concerns.
6. Offer alternatives.
7. Make sure to submit your comments by the comment period deadline
identified.
8. To ensure proper receipt by EPA, identify the appropriate docket
identification number, OAR-2002-0064 in the subject line on the first
page of your response. It would also be helpful if you provided the
name, date, and Federal Register citation related to your comments.
EPA invites comment on all aspects of today's proposed rule. A
number of specific issues are raised throughout the SUPPLEMENTARY
INFORMATION section of today's preamble. We request your comments on
the following issues in particular:
(1) Is it appropriate for EPA to find nPB acceptable for use in the
solvents metals, electronics and precision cleaning, aerosol solvents,
and adhesives, coatings, and inks sectors? Why or why not? Should EPA
have different decisions for different sectors or end uses? In
particular, given that the CERHR Expert Panel expressed concern about
``poorly controlled spray adhesive applications,'' should EPA find nPB
acceptable, subject to use conditions, for use in spray adhesives?
Should the Agency find nPB acceptable, subject to use conditions, for
use in aerosol solvents, or should nPB's use be limited to certain
applications in this end use? (See section III of today's notice and
CERHR, 2002a, p. 50.)
(2) What is an appropriate and achievable limit on the content of
isopropyl bromide (iPB) in unstabilized nPB? Should this impurity limit
be 0.1%, 0.05%, or 0.025% iPB by weight? Why? How much does each of
these purity levels add to the cost of cleaning solvents or adhesives
made using nPB, in terms of $/drum and as a percentage of the current
cost? (See section IV.A.4. of today's notice.)
(3) What is an appropriate acceptable exposure limit for EPA to
recommend, and why? If you disagree with the proposed recommended
exposure limit of 25 ppm, why do you disagree? Should EPA consider risk
management principles in developing a recommended AEL? Please cite
specific points of concern (e.g., studies considered, endpoints
considered in BMD analysis, uncertainty factors applied). (See sections
IV.A.1.a through d. of today's notice.)
(4) Should nPB be listed acceptable with a skin notation? (See
section IV.A.1.b of today's notice.)
EPA also invites commenters to submit any new, relevant data
pertaining to nPB and iPB beyond what is discussed in today's notice.
Under EPA guidelines, there is a preference for peer reviewed data
because of the potential to improve the quality and credibility of the
product. Peer-reviewed data are studies/analyses that have been
reviewed by qualified individuals (or organizations) who are
independent of those who performed the work, but who are collectively
equivalent in technical expertise (i.e., peers) to those who
[[Page 33308]]
performed the original work. A peer review is an in-depth assessment of
the assumptions, calculations, extrapolations, alternate
interpretations, methodology, acceptance criteria, and conclusions
pertaining to the specific major scientific and/or technical work
products and of the documentation that supports them (US EPA, 2000b).
To ensure that we have time to consider your comments, please
submit them to EPA's Air Docket by the date in the DATES section at the
beginning of this document. You may submit them via e-mail to [email protected]. Comments may be submitted electronically, by mail, by
facsimile, or through hand delivery/courier. Follow the detailed
instructions provided in sections I.B through I.D. To give us more time
to consider your comments, please also send a copy via e-mail to our
staff directly at [email protected]. EPA's responses to
comments, whether the comments are written or electronic, will be in a
final rule published in the Federal Register or in a response-to-
comments document placed in the rulemaking docket. We will not reply to
respondents electronically other than to seek clarification of
electronic comments that may be disrupted in transmission or during
conversion to paper form.
VIII. What Is the Federal Government Doing To Help Businesses Use nPB
Safely?
EPA is concerned that careless use of nPB will place those exposed
at risk of serious adverse health effects. We are also concerned that
some users perceive nPB as a ``path of less resistance'' because it has
similar properties to methyl chloroform, but, unlike methyl chloroform,
OSHA has not issued a permissible exposure limit (PEL) for nPB. In
particular, the adhesives industry widely used methyl chloroform and
then methylene chloride as carrier solvents. Since the introduction of
OSHA workplace regulations for methylene chloride, some companies
appear to prefer nPB-based adhesives because nPB is not yet regulated,
and because nPB is not flammable under normal conditions. Because of
these concerns, EPA is working with NIOSH to develop outreach materials
to share with facilities that use, or could use, nPB to inform them of
good workplace practices.
Further, EPA recommends that users contact OSHA's consultation
service. OSHA funds confidential consultation services to users through
state government staff. Employers can find out about potential hazards
at their worksites, improve their occupational safety and health
management systems, and even qualify for a one-year exemption from
routine OSHA inspections. The consultation service is separate from
inspections and enforcement. To request a consultation, telephone or
write to the appropriate state consultation service, listed on the web
at http://www.osha.gov/oshdir/consult.html. For example, if you have a
facility in North Carolina, call the North Carolina Department of Labor
at (919) 807-2899. See OSHA's web site at http://www.osha.gov/html/consultation.html for further information on consultation services.
IX. How Can I Use nPB as Safely as Possible?
As discussed above in section IV.A.1.e, EPA believes that the AEL
of 25 ppm can be met in all the industrial sectors being reviewed
today, including solvent cleaning applications, adhesives applications,
and aerosol solvents applications, as long as appropriate controls are
put in place. However, EPA also realizes that this exposure guideline
is relatively low and that in many cases, users will have to implement
additional emissions control measures to reach this level. Below are
actions that will help nPB users meet the exposure guideline
recommended in today's proposed rule:
[sbull] All users of nPB should wear appropriate personal
protective equipment, including chemical goggles, flexible laminate
protective gloves and chemical-resistant clothing. Special care should
be taken to avoid contact with the skin since nPB, like many
halogenated solvents, can be absorbed through the skin.
[sbull] Follow guidelines in the National Emission Standard for
Hazardous Air Pollutants (NESHAP) for halogenated solvents cleaning if
you are using nPB for non-aerosol solvent cleaning. The equipment and
procedural changes described in the halogenated solvents NESHAP can
reduce emissions, reduce solvent losses and lower the cost of cleaning
with organic solvents. For more information on the halogenated solvents
NESHAP, visit http://www.epa.gov/ttn/atw/eparules.html and http://www.epa.gov/ttn/atw/degrea/halopg.html.
[sbull] Use the employee exposure monitoring programs and product
stewardship programs where offered by manufacturers and formulators of
nPB-based solvents and adhesives.
[sbull] Follow all recommended safety precautions specified in the
manufacturer's Material Safety Data Sheets (MSDSs).
[sbull] Use sufficient ventilation and emissions controls to meet
the 25 ppm AEL in adhesives or aerosol applications (or, once
developed, the applicable OSHA PEL). Examples of ventilation equipment
for aerosol uses include ventilation hoods and fans. Adhesive appliers
can use spray booths, ventilation hoods or ducts, and fans to reduce
exposure.
[sbull] Request a confidential consultation from your State
government. You can contact the appropriate state agency that
participates in OSHA's consultation program. These contacts are on
OSHA's Web site at http://www.osha.gov/oshdir/consult.html. For further
information on OSHA's confidential consultancy program, visit OSHA's
web page at http://www.osha.gov/html/consultation.html.
[sbull] If the manufacturer or formulator of your nPB-based product
does not have an exposure monitoring program, we recommend that you
start your own exposure monitoring program, and/or request a
confidential consultation from your State government.
[sbull] A medical monitoring program should be established for the
early detection and prevention of acute and chronic effects of exposure
to nPB. The workers' physician(s) should be given information about the
adverse health effects of exposure to nPB and the workers' potential
for exposure.
[sbull] Workers should receive safety training and education that
includes potential health effects of exposure to nPB, covering
information included on the appropriate material data safety sheets, as
required by OSHA's Hazard Communication Standard (29 CFR 1910.1200).
We note that these steps are useful for reducing exposure to any
industrial solvent, and not just nPB.
X. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
Under Executive Order 12866, (58 FR 51735; October 4, 1993) the
Agency must determine whether the regulatory action is ``significant''
and therefore subject to the Office of Management and Budget (OMB)
review and the requirements of the Executive Order. The Order defines
``significant regulatory action'' as one that is likely to result in a
rule that may: (1) Have an annual effect on the economy of $100 million
or more or adversely affect in a material way the economy, a sector of
the economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or tribal
[[Page 33309]]
governments or communities; (2) create a serious inconsistency or
otherwise interfere with an action taken or planned by another agency;
(3) materially alter the budgetary impact of entitlement, grants, user
fees, or loan programs or the rights and obligations of recipients
thereof; or (4) raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
Pursuant to the terms of Executive Order 12866, OMB notified EPA
that it considers this action a ``significant regulatory action''
within the meaning of the Executive Order, and EPA submitted this
action to OMB for review. Changes made in response to OMB suggestions
or recommendations have been documented in the public record.
B. Paperwork Reduction Act
This action does not impose any new information collection burden.
Today's proposal is an Agency determination. It contains no new
requirements for reporting. The only new recordkeeping requirement
involves customary business practice. The Office of Management and
Budget (OMB) has previously approved the information collection
requirements contained in the existing regulations in subpart G of 40
CFR part 82 under the provisions of the Paperwork Reduction Act, 44
U.S.C. 3501 et seq. and has assigned OMB control numbers 2060-0226 (EPA
ICR No. 1596.05). This ICR included five types of respondent reporting
and record-keeping activities pursuant to SNAP regulations: submission
of a SNAP petition, filing a SNAP/TSCA Addendum, notification for test
marketing activity, record-keeping for substitutes acceptable subject
to use restrictions, and record-keeping for small volume uses. Today's
proposed rule, if finalized, would require minimal record-keeping for
two years from the date of creation of the record to demonstrate that
the nPB contains no more than 0.05% iPB. Because it is customary
business practice that chemical companies provide certificates of
analysis to their customers, we believe this requirement will not
impose an additional paperwork burden.
Copies of the ICR document(s) may be obtained from Sandy Farmer, by
mail at the Office of Environmental Information, Collection Strategies
Division; U.S. Environmental Protection Agency (2822); 1200
Pennsylvania Ave., NW., Washington, DC 20460, by e-mail at
[email protected], or by calling (202) 566-1676. A copy may also be
downloaded off the Internet at http://www.epa.gov/icr. Include the ICR
and/or OMB number in any correspondence.
Burden means the total time, effort, or financial resources
expended by persons to generate, maintain, retain, or disclose or
provide information to or for a Federal agency. This includes the time
needed to review instructions; develop, acquire, install, and utilize
technology and systems for the purposes of collecting, validating, and
verifying information, processing and maintaining information, and
disclosing and providing information; adjust the existing ways to
comply with any previously applicable instructions and requirements;
train personnel to be able to respond to a collection of information;
search data sources; complete and review the collection of information;
and transmit or otherwise disclose the information.
An Agency may not conduct or sponsor, and a person is not required
to respond to, a collection of information unless it displays a
currently valid OMB control number. The OMB control numbers for EPA's
regulations are listed in 40 CFR part 9 and 48 CFR chapter 15.
C. Regulatory Flexibility Act (RFA)
The RFA generally requires an agency to prepare a regulatory
flexibility analysis of any rule subject to notice and comment
rulemaking requirements under the Administrative Procedure Act or any
other statute unless the agency certifies that the rule will not have a
significant economic impact on a substantial number of small entities.
Small entities include small businesses, small organizations, and small
governmental jurisdictions. For purposes of assessing the impacts of
today's rule on small entities, small entity is defined as: (1) A small
business that has fewer than 500 employees; (2) a small governmental
jurisdiction that is a government of a city, county, town, school
district or special district with a population of less than 50,000; and
(3) a small organization that is any not-for-profit enterprise which is
independently owned and operated and is not dominant in its field. EPA
has consulted with the Small Business Administration's Office of
Advocacy on the alternate small business definition of 500 employees.
For today's rule, we chose to use 500 employees, rather than use the
individual size standards for the numerous NAICS subsectors and codes
to simplify the economic analysis. Furthermore, this size standard was
set by SBA for all NAICS codes for businesses using nPB-based
adhesives, which is the end use that could experience the greatest cost
impacts under today's rule. We solicit comments on the choice of this
alternate definition for this analysis.
After considering the economic impacts of today's proposed rule on
small entities, I certify that this action will not have a significant
economic impact on a substantial number of small entities.
Types of businesses that would be subject to today's proposed rule,
if it became final, would include:
[sbull] Manufacturers of computers and electronic equipment that
clean with nPB cleaning solvents (NAICS subsector 334).
[sbull] Manufacturers of fabricated metal parts, including plating,
ball and roller bearings, machined parts, and other metal parts that
require oil and grease to be cleaned off (NAICS subsectors 332 and
333).
[sbull] Manufacturers of transportation equipment, such as
aerospace equipment that requires cleaning either in a tank or with
aerosols, and aircraft seating, which is assembled using adhesives
containing nPB as a carrier solvent (NAICS subsector 336).
[sbull] Manufacturers of furniture, including various kinds of
furniture with cushions and countertops assembled using adhesives
containing nPB as a carrier solvent (NAICS subsector 337).
[sbull] Foam fabricators, who assemble foam cushions using
adhesives containing nPB as a carrier solvent (NAICS code 326150).
EPA estimates that up to 7330 small industrial end users currently
use nPB and thus could be subject to this rule. This number includes
approximately 500 to 2300 users of nPB industrial cleaning solvents
(e.g., cleaning with vapor degreasers), 900 to 4750 users of nPB-based
aerosol solvents, and 40 to 280 users of nPB-based adhesives.
In order to consider the resources that affected small businesses
have available to operate and to respond to regulatory requirements,
EPA compared the cost of meeting regulatory requirements to small
businesses' annual sales. In our analysis for today's proposal, we used
the average value of shipments for the products manufactured by the end
user as a proxy for sales or revenues, since these data are readily
available from the U.S. Department of Commerce. The following tables
display the average value of shipments for different sizes of business
and different NAICS subsectors or codes in the affected industrial
sectors. EPA then used data from these sources to determine the
potential economic impacts on small businesses of today's proposed
rule.
[[Page 33310]]
Table 4.--Average Value of Shipments in NAICS Subsectors Performing Solvent Cleaning \1\, by Number of Employees
at Business
----------------------------------------------------------------------------------------------------------------
Average value of shipments per company ($) by NAICS subsector code
-------------------------------------------------------------------------------
Number of employees at business 332, 334, Computer 336, 337, Furniture
Fabricated 333, Machinery and electronic Transportation and related
metal products products equipment products
----------------------------------------------------------------------------------------------------------------
1-4............................. 174,832 230,806 279,683 d \2\ 141,654
5-9............................. d \2\ 766,045 903,756 d \2\ 501,193
10-19........................... 1,393,019 d \2\ 1,925,077 1,897,347 1,102,104
20-49........................... 3,596,222 d \2\ 4,270,554 4,190,678 2,744,633
50-99........................... 9,283,654 10,429,360 10,440,847 10,140,871 6,908,332
100-249......................... 24,566,631 25,781,244 d \2\ 27,861,502 17,898,851
250-499......................... 55,392,738 64,822,617 d \2\ 69,529,351 d \2\
-----------------
Average--All Small Businesses in 3.2 million 4.2 million 2.4 million 8.9 million 1.7 million
Subsector......................
-----------------
Average--All Businesses in 3.9 million 8.9 million 25.2 million 44.6 million 3.1 million
Subsector......................
----------------------------------------------------------------------------------------------------------------
\1\ Aerosol solvents are used in NAICS subsectors 334 and 336. Non-aerosol solvents are used in all five NAICS
subsectors.
\2\ ``d'' designates ``Data withheld to avoid disclosing data of individual companies; data are included in
higher level totals.'' The average value of shipments for small businesses does not include those values
marked with ``d,'' and thus may be overestimated or underestimated.
Table 5.--Average Value of Shipments in NAICS Categories Using nPB as a Carrier Solvent in Adhesives, by Number
of Employees at Business
----------------------------------------------------------------------------------------------------------------
Average Value of Shipments per Small Company ($) by NAICS Code
-------------------------------------------------------------------------------
326150,
337121, 337110, Wood Urethane and 336360, Motor
Number of employees at business Upholstered kitchen other foam vehicle 337124, Metal
household cabinet and products seating and household
furniture counter tops (except interior trim furniture
polystyrene)
----------------------------------------------------------------------------------------------------------------
1-4............................. 135,545 135,046 287,744 174,500 170,820
5-9............................. 428,646 457,310 1,211,200 532,875 582,725
10-19........................... 913,225 1,015,967 2,537,028 2,490,455 1,299,671
20-49........................... 2,582,340 2,326,857 5,892,653 3,901,979 3,730,479
50-99........................... 5,680,148 5,655,585 11,608,984 8,981,786 7,522,129
100-249......................... 14,832,151 16,139,988 26,480,552 44,153,730 16,911,474
250-499......................... d 47,943,433 59,104,111 100,579,000 33,330,714
-----------------
Average--All Small Businesses in 3.3 million 0.9 million 9.4 million 18.3 million 4.1 million
NAICS Code.....................
-----------------
Average--All Businesses in NAICS 4.9 million 1.1 million 10.1 million 29.1 million 6.0 million
Code...........................
----------------------------------------------------------------------------------------------------------------
Today's proposed rule would require that users use nPB that
contains no more than 0.05% iPB by weight. Most chemical manufacturers
and solvent formulators already make products that meet this
requirement. Some users of adhesives containing nPB use formulations
that do not meet the proposed limit on iPB content. These users may
need to purchase a more expensive grade of nPB-based adhesives that
contains less iPB. Many users of adhesives containing nPB are small
businesses that fabricate foam to be used in cushions for furniture.
If the requirements of today's proposed rule were to be finalized,
we estimate that between 0 and 13 small businesses using nPB-based
adhesives, or less than 5% of the 280 or so small businesses that use
nPB-based adhesives, would experience a cost increase (i.e., an impact)
of greater than 1.0% of annual sales. Because solvent and aerosol
solvent formulations of nPB already contain less than 0.05% iPB by
weight, there were no impacts on end users in the non-aerosol solvent
cleaning sector and aerosol solvents end use; only the 0 to 13 adhesive
end users experienced a significant impact. An even smaller percentage
of all 7330 or so small businesses choosing to use nPB would experience
an impact of greater than 1.0% of annual sales. In addition, we
estimate that no small businesses would experience an impact of greater
than 3.0% of annual sales. We conclude that no small business subject
to today's rule would go out of business as a result of the rule's
requirements, if they were to become final. Because of the small total
number and small percentage of affected businesses that would
experience an impact of greater than either 1.0% or 3.0% of annual
sales, EPA does not consider this rule to have a significant impact on
a substantial number of small businesses.
The recommended acceptable exposure limit is only a recommendation
and not an enforceable requirement of today's rule, and thus, EPA is
not required to analyze the cost associated with implementing the
recommended exposure limit. Nevertheless, the Agency did analyze the
cost impacts of the combination of implementing the exposure limit and
complying with the regulatory use condition in order to provide
additional information about potential effects on small businesses. We
found that, when the costs to comply with the regulatory use condition
and to implement the recommended acceptable exposure limit are
considered together, at most 47 small businesses choosing to use nPB
would experience an impact of greater
[[Page 33311]]
than 1.0% of annual sales, and none would experience an impact of
greater than 3.0% of annual sales. All of the small businesses that
would experience significant impacts are users of nPB-based adhesives.
Thus, slightly less than 17% of the 280 or so small businesses choosing
to use nPB-based adhesives would experience significant impacts, and
less than 1% of all 7330 or so small businesses choosing to use nPB
would experience significant impacts. Based on the relatively small
number and percentage of small businesses that would experience
significant impacts, EPA concludes that even if costs of implementing
the recommended exposure limit were considered together with costs of
complying with the regulatory use condition, today's rule would not
have a significant impact on a substantial number of small entities.
Although this proposed rule will not have a significant economic
impact on a substantial number of small entities, EPA nonetheless has
tried to reduce the impact of this rule on small entities. Before
selecting the regulatory options proposed today, we considered a number
of regulatory options that would have had greater impacts on small
businesses, such as:
[sbull] Finding nPB unacceptable for use in adhesives. This
approach would require hundreds of small businesses to use other types
of adhesives, with no option to improve ventilation to reduce worker
exposure. Although small businesses could potentially save money by
using a less expensive adhesive, such as a flammable adhesive, the
capital costs of fire-proofing currently discourage small businesses
from using inexpensive flammable adhesives. In addition, requirements
of the Federal Aviation Administration for aircraft seating cushions
effectively require either using nPB-based or methylene chloride-based
adhesive or receiving a special waiver from the Administration. Recent
regulations for hazardous air pollutants disallow use of methylene
chloride in foam fabrication facilities. Thus, it is useful for
adhesive users to have the option of nPB-based adhesives.
[sbull] Placing a narrowed use limit on the use of nPB in adhesives
that would allow its use only in those cases where alternatives are
technically infeasible due to performance or safety issues.
[sbull] Requiring that users clean metal, electronics, or other
parts with nPB in vapor degreasing equipment that meets the
requirements of the national emission standards for halogenated solvent
cleaning.
In developing our regulatory options, we considered information we
learned from contacting small businesses using or selling nPB. EPA
staff visited the site of a small business using nPB for cleaning
electronics. We contacted several fabricators of foam cushions that
have used adhesives containing nPB. We participated in meetings with a
number of adhesive manufacturers and users of adhesives in furniture
construction. We have developed a fact sheet and have updated our
program web site to inform small businesses about this proposed rule
and to request their comments. We continue to be interested in the
potential impacts of the proposed rule on small entities and request
comments on issues related to such impacts.
D. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public
Law 104-4, establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and tribal
governments and the private sector. Under section 202 of the UMRA, EPA
generally must prepare a written statement, including a cost-benefit
analysis, for proposed and final rules with ``Federal mandates'' that
may result in expenditures to State, local, and tribal governments, in
the aggregate, or to the private sector, of $100 million or more in any
one year. Before promulgating an EPA rule for which a written statement
is needed, section 205 of the UMRA generally requires EPA to identify
and consider a reasonable number of regulatory alternatives and adopt
the least costly, most cost-effective or least burdensome alternative
that achieves the objectives of the rule. The provisions of section 205
do not apply when they are inconsistent with applicable law. Moreover,
section 205 allows EPA to adopt an alternative other than the least
costly, most cost-effective or least burdensome alternative if the
Administrator publishes with the final rule an explanation why that
alternative was not adopted. Before EPA establishes any regulatory
requirements that may significantly or uniquely affect small
governments, including tribal governments, it must have developed under
section 203 of the UMRA a small government agency plan. The plan must
provide for notifying potentially affected small governments, enabling
officials of affected small governments to have meaningful and timely
input in the development of EPA regulatory proposals with significant
Federal intergovernmental mandates, and informing, educating, and
advising small governments on compliance with the regulatory
requirements. EPA has determined that this rule does not contain a
Federal mandate that may result in expenditures of $100 million or more
for State, local, and tribal governments, in the aggregate, or the
private sector in any one year. Today's proposed rule does not affect
State, local, or tribal governments. The enforceable requirements of
the rule for the private sector affect only a small number of
manufacturers and importers of nPB in the United States, and most of
them already claim to meet the proposed standard prior to regulation.
Therefore, the impact of this rule on the private sector is less than
$100 million per year. Thus, today's rule is not subject to the
requirements of sections 202 and 205 of the UMRA. EPA has determined
that this rule contains no regulatory requirements that might
significantly or uniquely affect small governments. This regulation
applies directly to facilities that use these substances and not to
governmental entities.
E. Executive Order 13132: Federalism
Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August
10, 1999), requires EPA to develop an accountable process to ensure
``meaningful and timely input by State and local officials in the
development of regulatory policies that have federalism implications.''
``Policies that have federalism implications'' is defined in the
Executive Order to include regulations that have ``substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government.''
This proposed rule does not have federalism implications. It will
not have substantial direct effects on the States, on the relationship
between the national government and the States, or on the distribution
of power and responsibilities among the various levels of government,
as specified in Executive Order 13132. This regulation applies directly
to facilities that use these substances and not to governmental
entities. Thus, Executive Order 13132 does not apply to this rule.
F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
Executive Order 13175, entitled ``Consultation and Coordination
with Indian Tribal Governments'' (65 FR 67249, November 6, 2000),
requires EPA to develop an accountable process to ensure ``meaningful
and timely input by tribal officials in the development of regulatory
policies that have tribal implications.'' ``Policies that have tribal
[[Page 33312]]
implications'' is defined in the Executive Order to include regulations
that have ``substantial direct effects on one or more Indian tribes, on
the relationship between the Federal government and the Indian tribes,
or on the distribution of power and responsibilities between the
Federal government and Indian tribes.''
This proposed rule does not have tribal implications. It will not
have substantial direct effects on tribal governments, on the
relationship between the Federal government and Indian tribes, or on
the distribution of power and responsibilities between the Federal
government and Indian tribes, as specified in Executive Order 13175.
Today's proposed rule does not significantly or uniquely affect the
communities of Indian tribal governments, because this regulation
applies directly to facilities that use these substances and not to
governmental entities. Thus, Executive Order 13175 does not apply to
this proposed rule.
G. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks
Executive Order 13045: ``Protection of Children from Environmental
Health Risks and Safety Risks'' (62 FR 19885, April 23, 1997) applies
to any rule that: (1) Is determined to be ``economically significant''
as defined under Executive Order 12866, and (2) concerns an
environmental health or safety risk that EPA has reason to believe may
have a disproportionate effect on children. If the regulatory action
meets both criteria, the Agency must evaluate the environmental health
or safety effects of the planned rule on children, and explain why the
planned regulation is preferable to other potentially effective and
reasonably feasible alternatives considered by the Agency.
This proposed rule is not subject to the Executive Order because it
is not economically significant as defined in Executive Order 12866,
and because the Agency does not have reason to believe the
environmental health or safety risks addressed by this action present a
disproportionate risk to children. The exposure limits and
acceptability listings in this proposed rule apply to the workplace.
These are areas where we expect adults are more likely to be present
than children, and thus, the agents do not put children at risk
disproportionately.
Further, today's proposed rule provides both regulatory
restrictions and recommended exposure guidelines based upon
toxicological studies in order to reduce risk of exposure to
reproductive toxins, both iPB and nPB. This rule is not subject to
Executive Order 13045 because it is not economically significant as
defined in Executive Order 12866 and because the Agency does not have
reason to believe the environmental health or safety risks addressed by
this action present a disproportionate risk to children. The public is
invited to submit or identify peer-reviewed studies and data, of which
the agency may not be aware, that assessed results of early life
exposure to nPB or iPB.
H. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution, or Use
This proposed rule is not a ``significant energy action'' as
defined in Executive Order 13211, ``Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use'' (66 FR 28355
(May 22, 2001)) because it is not likely to have a significant adverse
effect on the supply, distribution, or use of energy. This action would
impact manufacturing of various metal, electronic, medical, and optical
products cleaned with solvents containing nPB and products made with
adhesives containing nPB. Further, we have concluded that this rule is
not likely to have any adverse energy effects.
I. National Technology Transfer and Advancement Act
Section 12(d) of the National Technology Transfer and Advancement
Act of 1995 (``NTTAA''), Public Law 104-113, Section 12(d) (15 U.S.C.
272 note) directs EPA to use voluntary consensus standards in
regulatory activities unless to do so would be inconsistent with
applicable law or otherwise impractical. Voluntary consensus standards
are technical standards (e.g., materials specifications, test methods,
sampling procedures, and business practices) that are developed or
adopted by voluntary consensus standards bodies. The NTTAA directs EPA
to provide Congress, through OMB, explanations when the Agency decides
not to use available and applicable voluntary consensus standards. This
proposed rulemaking involves technical standards since EPA is proposing
to limit the amount of iPB as a contaminant of nPB formulations to
0.05%, which is lower than the 0.1% limit set by the ASTM standard for
vapor degreasing grade and general grade nPB. Based on the relatively
potent toxicity of iPB (see discussion in section IV.A.4 of the
preamble), EPA believes it is prudent to reduce the level of iPB to
0.05% to protect worker health. EPA has consulted with producers and
formulators of nPB products, and all have stated that an iPB limit of
0.05% is achievable. EPA requests comment on this aspect of the
proposed rulemaking and, specifically, invites the public to comment on
the level of iPB contamination that EPA should set, and to explain why
such limits should be set in this regulation.
XI. References
The documents below are referenced in the preamble. All documents
are located in the Air Docket at the address listed in section I.B.1 at
the beginning of this document. Unless specified otherwise, all
documents are available in hard copy in docket number A-2001-07 (legacy
docket number for Docket ID No. OAR-2002-0064). Numbers listed after
the reference indicate the item number within the docket.
Flammability
UNEP, 1999. 1998 Report of the United Nations Environment Programme
Ozone Secretariat, Solvents, Coatings and Adhesives Technical Options
Committee, April, 1999. (II-A-22)
Ozone-Depletion Potential and Global Warming Potential
Atmospheric and Environmental Research, Inc., 1995: Estimates of the
Atmospheric Lifetime, Global Warming Potential and Ozone Depletion
Potential of n-Propyl Bromide. Independent study prepared for Albemarle
Corporation. (II-D-17)
WMO (World Meteorological Organization), 1999: Scientific Assessment of
Ozone Depletion: 1998, Global Ozone Research and Monitoring Project--
Report No. 44, Geneva, 1998. (II-A-20)
Wuebbles, D. J., R. Kotamarthi, and K. O. Patten, 1999: ``Updated
evaluation of Ozone Depletion Potentials for Chlorobromomethane and 1-
bromo-propane.'' Atmospheric Environment, Vol. 33, p. 1641-1643. (A-91-
42, IX-A-62)
Wuebbles, D. J., K. O. Patten, and M. T. Johnson, 2000: ``Effects of n-
propyl bromide and other short-lived chemicals on stratospheric
ozone.'' Proceedings, Symposium on Atmospheric Chemistry Issues in the
21st Century, American Meteorological Society, Boston. (II-A-4)
Wuebbles, Donald J., Patten, Kenneth O., Johnson, Matthew T.,
Kotamarthi, Rao, 2001: ``New methodology for Ozone Depletion Potentials
of short-lived compounds: n-propyl bromide as an example.'' Journal of
[[Page 33313]]
Geophysical Research, Vol. 106, No. D13, p. 14,551. (II-A-3)
Wuebbles, Donald J. 2002. ``The Effect of Short Atmospheric Lifetimes
on Stratospheric Ozone.'' Written for Enviro Tech International, Inc.
Department of Atmospheric Sciences, University of Illinois-Urbana. (II-
D-29)
Toxicity
Albemarle, 1997. Attachment 5 to August 7, 1997 submission to EPA, Air
Monitoring Data. (Docket A-91-42, item VI-D-114)
Albemarle, 2001. November 16, 2001 e-mail from Mick Kassem, Albemarle
Corporation, concerning exposure levels using nPB in various
applications. (II-A-19)
Amity UK Ltd, 2001. Amity Product Information Bulletin Sheet Ref. No.
00-003: Vapor Degreasing Good Practice. 5 June 2001. (II-A-18)
Barber E.D., Donish W., Mueller K. 1981. A procedure for the
quantitative measurement of the mutagenicity of volatile liquids in the
Ames Salmonella/microsome assay. Mutat Res 90:31-48. (II-A-9)
Barber E., Donish W. 1982. An exposure system for quantitative
measurements of the microbial mutagenicity of volatile liquids in
genotoxic effects of airborne agents. Environ Sci Res 25:3-18. (II-A-
29)
Brock, W. 2002. Letter to Jeff Cohen, EPA re: Comments on Acceptable
Exposure Limit Derivation for n-Propyl Bromide (II-D-57)
Biles, 2002. Personal communication between Jeff Cohen, EPA and Blake
Biles, Arnold & Porter, counsel to the Brominated Solvents Consortium
(II-B-18)
CCPCT (The Center for Clean Products and Clean Technologies) August
2001. Alternative Adhesive Technologies in the Foam Furniture and
Bedding Industries: A Cleaner Technologies Substitutes Assessment.
Volume 2: Risk Screening and Comparison. The University of Tennessee
Center for Clean Products and Clean Technologies. (II-D-70)
CERHR, 2002a. NTP-Center for the Evaluation of Risks to Human
Reproduction Expert Panel Report on the Reproductive and Developmental
Toxicity of 1-Bromopropane [nPB]. March 2002. (II-A-11)
CERHR, 2002b. NTP-Center for the Evaluation of Risks to Human
Reproduction Expert Panel Report on the Reproductive and Developmental
Toxicity of 2-Bromopropane [iPB]. March 2002. (II-A-12)
Charm, 2001. Letter to Dov Shellef, President, Poly Systems USA, Inc.
from Joel Charm CIH, Charm HS&E International Inc. re: n-Propyl Bromide
(II-D-16).
ClinTrials, 1997a. A 28-Day Inhalation Study of a Vapor-Formulation of
ALBTA1 in the Albino Rat. Report No. 91189. Prepared by ClinTrials
BioResearch Laboratories, Ltd., Senneville, Quebec, Canada. May 15,
1997. Sponsored by Albemarle Corporation, Baton Rouge, LA. (A-91-42, X-
A-4)
ClinTrials, 1997b. ALBTA1: A 13-Week Inhalation Study of a Vapor
Formulation of ALBTA1 in the Albino Rat. Report No. 91190. Prepared by
ClinTrials BioResearch Laboratories, Ltd., Senneville, Quebec, Canada.
February 28, 1997. Sponsored by Albemarle Corporation, Baton Rouge, LA.
(A-91-42, X-A-5)
Crump, K.S. 1984. A new method for determining allowable daily intakes.
Fundam. Appl. Toxicol. 4:854-871. (II-A-30)
Dodd, D. 2002. Letter to Jeff Cohen, EPA re: Comments on Acceptable
Exposure Limit Derivation for n-Propyl Bromide (II-D-56)
Elf Atochem, 1995. Micronucleus Test by Intraperitoneal Route in Mice.
n-Propyl Bromide. Study No. 12122 MAS. Study Director, Brigitte
Molinier. Study performed by Centre International de Toxoicologie,
Misery, France, September 6, 1995. (A-91-42, X-A-9)
Fiala ES, Sodum RS, Hussain NS, Rivenson A, Dolan L. 1995. Secondary
nitroalkanes: induction of DNA repair in rat hepatocytes, activation by
aryl sulfotransferase and hepatocarcinogenicity of 2-nitrobutane and 3-
nitropentane in male F344 rats. Toxicology May 5; 99(1-2):89-97. (A-91-
42, X-A-16)
Griffin, E., Wilson D. Disorders of the Testes. In: Isselbacher K,
Baunwald E, Wilson J, Martin B., et al. eds. Harrison's Principles of
Internal Medicine. 13th ed. New York, McGraw Hill; 1994: 2006-2017.
(II-A-35)
HESIS, 2002. Comments on ICF's proposed AEL for 1-Bromopropane from Dr.
Julia Quint, California Department of Health Services, Hazard
Evaluation System & Information Service (II-D-62)
Huntingdon Life Sciences, August 23, 2001. A Developmental Toxicity
Study in Rat Via Whole Body Inhalation Exposure. (II-D-27)
HSIA (Halogenated Solvents Industry Alliance), 2001. Minutes of EPA
meeting with Halogenated Solvents Industry Alliance, 10/17/2001. (II-B-
6)
IARC (International Agency for Research on Cancer), 1992. Monographs on
the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Some
Industrial Chemicals and Dyestuffs, Vol. 29, pages 331-343. (II-A-34)
ICF, Inc., 2001. ``Brief Discussion of the BMD Approach: Overview of
its Purpose, Methods, Advantages, and Disadvantages.'' Prepared for
U.S. EPA. (II-A-52)
ICF, Inc., 2002a. ``Risk Screen for Use of N Propyl Bromide.'' Prepared
for U.S. EPA, May, 2002. (II-A-13)
ICF, Inc. 2002c. ``Response to California HESIS comments on AEL for
nPB'' (II-A-55)
Ichihara G., Asaeda N., Kumazawa T., et al. 1997. Testicular and
hematopoietic toxicity of 2-bromopropane, a substitute for ozone layer-
depleting chlorofluorocarbons. J Occup Health 39:57-63. (A-91-42, X-A-
32)
Ichihara M., Takeuchi Y., Shibata E., Kitoh J., et al. 1998.
Neurotoxicity of 1-Bromopropane. Translated by Albemarle Corporation.
(A-91-42, X-A-33)
Ichihara G., Jong X., Onizuka J., et al. 1999. Histopathological
changes of nervous system and reproductive organ and blood biochemical
findings in rats exposed to 1-bromopropane. (Abstract only) Abstracts
of the 72nd Annual Meeting of Japan Society for Occupational Health.
May 1999. Tokyo. (II-A-15)
Ichihara G., Yu X., Kitoh J., et al. 2000a. Reproductive toxicity of 1-
bromopropane, a newly introduced alternative to ozone layer depleting
solvents, in male rats. Toxicol Sciences 54:416-423. (II-A-7)
Ichihara G., Kitoh J., Yu, X., et al. 2000b. 1-Bromopropane, an
alternative to ozone layer depleting solvents, is dose-dependently
neurotoxic to rats in long-term inhalation exposure. Toxicol Sciences
55:116-123. (II-A-8)
Ichihara G. et al., 2002a. Neurological Disorders in Three Workers
Exposed to 1-Bromopropane. J Occu. Health 44:1-7. (II-D-64)
Ichihara G. et al., 2002b. Poster presentation titled: ``Neurological
abnormality in workers of 1-bromopropane factory,'' Presented at the
Society of Toxicology Meeting, Wednesday, March 20, 2002. Poster
ID:1236. (II-D-35)
Kamijima M., Ichihara G., Kitoh J., et al. 1997a. Disruption in ovarian
cyclicity due to 2-bromopropane in the rat. J Occu. Health 39:3-4. (A-
91-42, X-A-35)
Kamijima M., Ichihara G., Kitoh J. et al. 1997b. Disruption in ovarian
cyclicity due to 2-bromopropane in the rat. J
[[Page 33314]]
Occu. Health 39:3-4. (A-91-42, X-A-35)
Kamijima M., Ichihara G., Kitoh J., et al. 1997b. Ovarian toxicity of
2-bromopropane in the nonpregnant female rat. J Occu. Health 39:144-
149. (A-91-42, X-A-36)
Kim Y., Jung K., Hwang T., Jung G., Kim H., Park J., Kim J., Park J.,
Park D., Park S., Choi K., Moon Y. 1996. Hematopoietic and reproductive
hazards of Korean electronic workers exposed to solvents containing 2-
bromopropane. Scand J Work Environ Health 22:387-391. (A-91-42, X-A-39)
Kim H.-Y., Chung Y.-H., Jeong J.-H., Lee Y.-M., Sur G.-S., Kang J.-K.
1999. Acute and repeated inhalation toxicity of 1-bromopropane in SD
rats. J Occup Health 41:121-128. (II-D-23)
Kimmel, C. and Gaylor, D. 1988. Issue in qualitative and quantitative
risk analysis for developmental toxicology. Risk Anal 8:15-21. (II-A-
28)
Kleinfelter, G. and Darney, S. 2002. Memorandum from EPA's Office of
Research and Development, Reproductive Toxicology Division, to J.
Cohen, Office of Air and Radiation, Comments on Acceptable Exposure
Limit for n-Propyl Bromide (II-C-1)
Maeng S.H., Yu I.J. 1997. Mutagenicity of 2-bromopropane. Ind Health
35:87-95. (A-91-42, X-A-47)
NIOSH, 1999. U.S. Dept. of Health and Human Services, Letter to Custom
Products Inc., December 1, 1999. Re: results of Dec. 1998 survey of
workplace exposure to nPB at Custom Products. (HHE Report 98-0153) (II-
D-6)
NIOSH, 2000a. U.S. Dept. of Health and Human Services, Letter to Marx
Industries, Inc., February 1, 2000. Re: results of nPB exposure
assessment survey conducted Nov. 16-17, 1999. (II-D-7)
NIOSH, 2000b. NIOSH Health Hazard Evaluation Report of nPB exposure
from cold vapor degreasers at Trilithic, Inc. (HHE Report 2000-0233-
2845) (II-D-11)
NIOSH, 2000c. U.S. Dept. of Health and Human Services, Letter to Custom
Products Inc., December 21, 2000. Re: results of nPB exposure
assessment survey conducted Nov. 16, 2000. (HHE Report 98-0153) (II-D-
8)
NIOSH, 2001. U.S. Dept. of Health and Human Services, Letter to STN
Cushion Company, March 7, 2001. Re: Results of nPB exposure assessment
survey conducted November 14, 2000. (II-D-9)
NIOSH, 2002. NIOSH Health Hazard Evaluation Report of nPB exposure from
spray adhesives at STN Cushion Company. August, 2002. (HHE Report 2000-
0410-2891) (II-A-31)
NIOSH, 2003. Comments of the National Institute for Occupational Safety
and Health of the draft Environmental Protection Agency Federal
Register Notice Protection of Stratospheric Ozone: Listing of
Substitutes for Ozone-Depleting Substances--n-Propyl Bromide (III-C-6)
Park, Jung-Sun et. al. 1997. ``An Outbreak of Hematopoietic and
Reproductive Disorders Due to Solvents Containing 2-Bromopropane in an
Electronic Factory, South Korea: Epidemiological Survey.'' J Occu.
Health 1997; 39: 138-143. (II-A-1)
Purvis K., Christiansen E., 1992, Male infertility: current concepts.
Ann Med 1992; 24:258-272. (II-A-36)
Rozman K. and Doull J., 2002. ``Derivation of an Occupational Exposure
Limit for n-Propyl Bromide Using an Improved Methodology'' App Occu.
Env. Hyg. 17: 711-716 (II-D-63)
Saito-Suzuki R., Teramoto S., Shirasu Y. 1982. Dominant lethal studies
in rats with 1,2-dibromo-3-chloropropane and its structurally related
compounds. Mutat Res 101:321-327. (A-91-42, X-A-55)
Sclar, 1999. Sclar, Gary, ``Case Report: Encephalomyeloradicu lo-
neuropathy following exposure to an industrial solvent'' Clinical
Neurology and Neurosurgery Vol. 01(1999) 99-202. (II-D-34)
Sekiguchi S., Suda M., Zhai Y.L., Honma T., ``Effects of 1-
bromopropane, 2-bromopropane, and 1,2-dichloropropane on the estrous
cycle and ovulation in F344 rats.'' Toxicol Lett 2002 Jan 5;126(1):41-9
(II-D-39)
SLR International Corp, 2001a. Human in vitro bioassays conducted by
EnviroMed Laboratories (II-D-2)
SLR International Corp., 2001b. ``Inhalation Occupational Exposure
Limit for n-Propyl Bromide.'' Prepared for Enviro Tech International,
Inc. 2001. (II-D-15)
US EPA, 1991a. Toxicity summary for 2-nitropropane. U.S. Environmental
Protection Agency. Integrated Risk Information System. Last updated 1
March 1991. (II-A-10)
US EPA, 1991b. Guidelines for Developmental Toxicity Risk Assessment.
U.S. Environmental Protection Agency. (II-A-51)
US EPA, 1994. U.S. Environmental Protection Agency (USEPA). 1994.
Methods for derivation of inhalation reference concentrations and
application of inhalation dosimetry. EPA/600/8-90/066F. Office of
Health and Environmental Assessment, Washington, DC. 1994. (II-A-16)
US EPA, 1995a. SCREEN3 air dispersion model. (II-A-53)
US EPA, 1995b. The Use of the Benchmark Dose Approach in Health Risk
Assessment. EPA/630-R-94-007. Risk Assessment Forum, Washington, DC.
(II-A-17)
US EPA, 2000b. Science Policy Council Handbook: Peer Review, 2nd
Edition. EPA Report 100-B-00-001, Office of Science Policy, Office of
Research and Development. December 2000. (II-A-46)
US EPA, 2002. E. Birgfeld, EPA, Letter transmitting comments on the
Expert Panel report of the Center for Evaluation of Risks to Human
Reproduction on 1-bromopropane and 2-bromopropane. May 9, 2002. (II-A-
14)
US EPA, 2003. EPA staff report, ``Economic Impacts: Options for SNAP
Decision on n-Propyl Bromide.'' (III-A-3)
Wang H., Ichihara G., Yamada T. 1999. Subacute effects of 1-
bromopropane on reproductive organs and the nervous system. Abstracts
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reproductive toxicity study of 1-bromopropane in rats.'' Sponsored by
the Brominated Solvent Consortium. May 24, 2001. (II-D-10)
Yamada T. et al., 2003. Exposure to 1-Bromopropane Causes Ovarian
Dysfunction in Rats. Toxicol Sci 71:96-103 (II-A-32)
Yu X, Ichihara G, Kitoh J, Xie Z, Shibata E, Kamijima M, Takeuchi Y.
2001. Neurotoxicity of 2-bromopropane and 1-bromopropane, alternative
solvents for chlorofluorocarbons. Environ Res 85(1):48-52. (II-D-20)
Potential Market, Lack of Regulatory Controls, and Economic Impacts
AFEAS (Alternative Fluorocarbon Environmental Acceptability Study),
2002. Data from the Web Site of the Alternative Fluorocarbon
Environmental Acceptability Study. 2002. (II-A-27)
Biles, 2001. Email from Blake Biles to Jeff Cohen on behalf of the
Brominated Solvents Consortium (BSOC). Contains the BSOC estimates of
world-wide nPB sales for the calendar years 2000, 2001, 2002. (II-D-18)
Institute for Research and Technical Assistance (IRTA), April 29, 1999.
Re: comments on nPB. (Docket A-91-42, item X-B-58)
[[Page 33315]]
Kassem, 2003. January 10, 2003 Letter from O. M. Kassem, Albemarle
Corporation to K. Bromberg, Small Business Administration Re: n propyl
bromine SNAP. (II-D-78)
UNEP (United Nations Environmental Programme), 2001: Geographic Market
Potential and Estimated Emissions of n-Propyl Bromide. Report by the
Technology and Economic Assessment Panel (TEAP) Task Force of the
Solvents, Coatings and Adhesives Technical Options Committee (STOC).
April, 2001. (II-A-21)
US EPA, 2003. EPA staff report, ``Economic Impacts: Options for SNAP
Decision on n-Propyl Bromide.'' (III-A-3)
Wolf, 2001. July 9, 2001, Letter from C. Wolf, Ultronix to M. Sheppard,
EPA (II-D-85)
List of Subjects in 40 CFR Part 82
Environmental protection, Administrative practice and procedure,
Air pollution control, Reporting and recordkeeping requirements.
Dated: May 21, 2003.
Christine Todd Whitman,
Administrator.
For the reasons set out in the preamble, 40 CFR part 82 is proposed
to be amended as follows:
PART 82--PROTECTION OF STRATOSPHERIC OZONE
1. The authority citation for part 82 continues to read as follows:
Authority: 42 U.S.C. 7414, 7601, 7671-7671q.
2. Subpart G is amended by adding the following appendix M to read
as follows:
Subpart G--Significant New Alternatives Policy Program
* * * * *
Appendix M to Subpart G--Substitutes Subject to Use Restrictions and
Unacceptable Substitutes Listed in the [publication date of final rule]
final rule
Solvent Cleaning Substitutes That are Acceptable Subject to Use Conditions
----------------------------------------------------------------------------------------------------------------
End use Substitute Decision Use condition Further information
----------------------------------------------------------------------------------------------------------------
Metals cleaning............... n-propyl bromide Acceptable nPB in this end use EPA expects that all
(nPB) as a subject to use shall not contain users of nPB will
substitute for conditions. more than 0.05% adhere to a
CFC-113 and isopropyl bromide by voluntary acceptable
methyl weight before adding exposure limit of 25
chloroform. stabilizers or other ppm on an 8-hour
chemicals. End users time-weighted
must keep records average. nPB is
documenting Number 106-94-5 in
compliance with this the CAS Registry.
condition for up to
two years from the
date on the
documentation.
Electronics cleaning.......... nPB as a Acceptable nPB in this end use EPA expects that all
substitute for subject to use shall not contain users of nPB will
CFC-113 and conditions more than 0.05% adhere to a
methyl isopropyl bromide by voluntary acceptable
chloroform. weight before adding exposure limit of 25
stabilizers or other ppm on an 8-hour
chemicals. End users time-weighted
must keep records average. nPB is
documenting Number 106-94-5 in
compliance with this the CAS Registry.
condition for up to
two years from the
date on the
documentation.
Precision cleaning............ nPB as a Acceptable nPB in this end use EPA expects that all
substitute for subject to use shall not contain users of nPB will
CFC-113 and conditions. more than 0.05% adhere to a
methyl isopropyl bromide by voluntary acceptable
chloroform. weight before adding exposure limit of 25
stabilizers or other ppm on an 8-hour
chemicals. End users time-weighted
must keep records average. nPB is
documenting Number 106-94-5 in
compliance with this the CAS Registry.
condition for up to
two years from the
date on the
documentation.
----------------------------------------------------------------------------------------------------------------
Note: In accordance with the limitations provided in section 310(a) of the Clean Air Act (42 U.S.C. 7610(a)),
nothing in this appendix shall affect the Occupational Safety and Health Administration's authority to enforce
standards and other requirements under the Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)
Aerosols Substitutes That Are Acceptable Subject to Use Conditions
----------------------------------------------------------------------------------------------------------------
End use Substitute Decision Use condition Further information
----------------------------------------------------------------------------------------------------------------
Aerosol solvents.............. n-propyl bromide Acceptable nPB in this end shall EPA expects that all
(nPB) as a subject to use not contain more users of nPB will
substitute for conditions. than 0.05% isopropyl adhere to a
CFC-113, HCFC- bromide by weight voluntary acceptable
141b, and before adding exposure limit of 25
methyl stabilizers or other ppm on an 8-hour
chloroform. chemicals. End users time-weighted
must keep records average. nPB is
documenting Number 106-94-5 in
compliance with this the CAS Registry.
condition for up to
two years from the
date on the
documentation.
----------------------------------------------------------------------------------------------------------------
Note: In accordance with the limitations provided in section 310(a) of the Clean Air Act (42 U.S.C. 7610(a)),
nothing in this appendix shall affect the Occupational Safety and Health Administration's authority to enforce
standards and other requirements under the Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)
[[Page 33316]]
Adhesives, Coatings, and Inks Substitutes That Are Acceptable Subject to Use Conditions
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End use Substitute Decision Use Condition Further information
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Adhesives..................... n-propyl bromide Acceptable nPB in this end use EPA expects that all
(nPB) as a subject to use shall not contain users of nPB will
substitute for conditions. more than 0.05% adhere to a
CFC-113, HCFC- isopropyl bromide by voluntary acceptable
141b, and weight before adding exposure limit of 25
methyl stabilizers or other ppm on an 8-hour
chloroform. chemicals. End users time-weighted
must keep records average. nPB is
documenting Number 106-94-5 in
compliance with this the CAS Registry.
condition for up to
two years from the
date on the
documentation.
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Note: In accordance with the limitations provided in section 310(a) of the Clean Air Act (42 U.S.C. 7610(a)),
nothing in this appendix shall affect the Occupational Safety and Health Administration's authority to enforce
standards and other requirements under the Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)
[FR Doc. 03-13254 Filed 6-2-03; 8:45 am]
BILLING CODE 6560-50-P