[Code of Federal Regulations]
[Title 29, Volume 6]
[Revised as of July 1, 2006]
From the U.S. Government Printing Office via GPO Access
[CITE: 29CFR1910.1001]
[Page 19-71]
TITLE 29--LABOR
CHAPTER XVII--OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT
OF LABOR
PART 1910_OCCUPATIONAL SAFETY AND HEALTH STANDARDS (CONTINUED)--Table of
Contents
Subpart Z_Toxic and Hazardous Substances
Sec. 1910.1001 Asbestos.
(a) Scope and application. (1) This section applies to all
occupational exposures to asbestos in all industries covered by the
Occupational Safety and Health Act, except as provided in paragraph
(a)(2) and (3) of this section.
(2) This section does not apply to construction work as defined in
29 CFR 1910.12(b). (Exposure to asbestos in construction work is covered
by 29 CFR 1926.1101).
(3) This section does not apply to ship repairing, shipbuilding and
shipbreaking employments and related employments as defined in 29 CFR
1915.4. (Exposure to asbestos in these employments is covered by 29 CFR
1915.1001).
(b) Definitions. Asbestos includes chrysotile, amosite, crocidolite,
tremolite asbestos, anthophyllite asbestos, actinolite asbestos, and any
of these minerals that have been chemically treated and/or altered.
Asbestos-containing material (ACM) means any material containing
more than 1% asbestos.
Assistant Secretary means the Assistant Secretary of Labor for
Occupational Safety and Health, U.S. Department of Labor, or designee.
Authorized person means any person authorized by the employer and
required by work duties to be present in regulated areas.
Building/facility owner is the legal entity, including a lessee,
which exercises control over management and record keeping functions
relating to a building and/or facility in which activities covered by
this standard take place.
Certified industrial hygienist (CIH) means one certified in the
practice of industrial hygiene by the American Board of Industrial
Hygiene.
Director means the Director of the National Institute for
Occupational Safety and Health, U.S. Department of Health and Human
Services, or designee.
Employee exposure means that exposure to airborne asbestos that
would occur if the employee were not using respiratory protective
equipment.
Fiber means a particulate form of asbestos 5 micrometers or
longer,with a
[[Page 20]]
length-to-diameter ratio of at least 3 to 1.
High-efficiency particulate air (HEPA) filter means a filter capable
of trapping and retaining at least 99.97 percent of 0.3 micrometer
diameter mono-disperse particles.
Homogeneous area means an area of surfacing material or thermal
system insulation that is uniform in color and texture.
Industrial hygienist means a professional qualified by education,
training, and experience to anticipate, recognize, evaluate and develop
controls for occupational health hazards.
PACM means ``presumed asbestos containing material.''
Presumed asbestos containing material means thermal system
insulation and surfacing material found in buildings constructed no
later than 1980. The designation of a material as ``PACM'' may be
rebutted pursuant to paragraph (j)(8) of this section.
Regulated area means an area established by the employer to
demarcate areas where airborne concentrations of asbestos exceed, or
there is a reasonable possibility they may exceed, the permissible
exposure limits.
Surfacing ACM means surfacing material which contains more than 1%
asbestos.
Surfacing material means material that is sprayed, troweled-on or
otherwise applied to surfaces (such as acoustical plaster on ceilings
and fireproofing materials on structural members, or other materials on
surfaces for acoustical, fireproofing, and other purposes).
Thermal System Insulation (TSI) means ACM applied to pipes,
fittings, boilers, breeching, tanks, ducts or other structural
components to prevent heat loss or gain.
Thermal System Insulation ACM means thermal system insulation which
contains more than 1% asbestos.
(c) Permissible exposure limit (PELS)--(1) Time-weighted average
limit (TWA). The employer shall ensure that no employee is exposed to an
airborne concentration of asbestos in excess of 0.1 fiber per cubic
centimeter of air as an eight (8)-hour time-weighted average (TWA) as
determined by the method prescribed in Appendix A to this section, or by
an equivalent method.
(2) Excursion limit. The employer shall ensure that no employee is
exposed to an airborne concentration of asbestos in excess of 1.0 fiber
per cubic centimeter of air (1 f/cc) as averaged over a sampling period
of thirty (30) minutes as determined by the method prescribed in
Appendix A to this section, or by an equivalent method.
(d) Exposure monitoring--(1) General. (i) Determinations of employee
exposure shall be made from breathing zone air samples that are
representative of the 8-hour TWA and 30-minute short-term exposures of
each employee.
(ii) Representative 8-hour TWA employee exposures shall be
determined on the basis of one or more samples representing full-shift
exposures for each shift for each employee in each job classification in
each work area. Representative 30-minute short-term employee exposures
shall be determined on the basis of one or more samples representing 30
minute exposures associated with operations that are most likely to
produce exposures above the excursion limit for each shift for each job
classification in each work area.
(2) Initial monitoring. (i) Each employer who has a workplace or
work operation covered by this standard, except as provided for in
paragraphs (d)(2)(ii) and (d)(2)(iii) of this section, shall perform
initial monitoring of employees who are, or may reasonably be expected
to be exposed to airborne concentrations at or above the TWA permissible
exposure limit and/or excursion limit.
(ii) Where the employer has monitored after March 31, 1992, for the
TWA permissible exposure limit and/or the excursion limit, and the
monitoring satisfies all other requirements of this section, the
employer may rely on such earlier monitoring results to satisfy the
requirements of paragraph (d)(2)(i) of this section.
(iii) Where the employer has relied upon objective data that
demonstrate that asbestos is not capable of being released in airborne
concentrations at or above the TWA permissible exposure limit and/or
excursion limit under the expected conditions of processing, use,
[[Page 21]]
or handling, then no initial monitoring is required.
(3) Monitoring frequency (periodic monitoring) and patterns. After
the initial determinations required by paragraph (d)(2)(i) of this
section, samples shall be of such frequency and pattern as to represent
with reasonable accuracy the levels of exposure of the employees. In no
case shall sampling be at intervals greater than six months for
employees whose exposures may reasonably be foreseen to exceed the TWA
permissible exposure limit and/or excursion limit.
(4) Changes in monitoring frequency. If either the initial or the
periodic monitoring required by paragraphs (d)(2) and (d)(3) of this
section statistically indicates that employee exposures are below the
TWA permissible exposure limit and/or excursion limit, the employer may
discontinue the monitoring for those employees whose exposures are
represented by such monitoring.
(5) Additional monitoring. Notwithstanding the provisions of
paragraphs (d)(2)(ii) and (d)(4) of this section, the employer shall
institute the exposure monitoring required under paragraphs (d)(2)(i)
and (d)(3) of this section whenever there has been a change in the
production, process, control equipment, personnel or work practices that
may result in new or additional exposures above the TWA permissible
exposure limit and/or excursion limit or when the employer has any
reason to suspect that a change may result in new or additional
exposures above the PEL and/or excursion limit.
(6) Method of monitoring. (i) All samples taken to satisfy the
monitoring requirements of paragraph (d) of this section shall be
personal samples collected following the procedures specified in
Appendix A.
(ii) All samples taken to satisfy the monitoring requirements of
paragraph (d) of this section shall be evaluated using the OSHA
Reference Method (ORM) specified in Appendix A of this section, or an
equivalent counting method.
(iii) If an equivalent method to the ORM is used, the employer shall
ensure that the method meets the following criteria:
(A) Replicate exposure data used to establish equivalency are
collected in side-by-side field and laboratory comparisons; and
(B) The comparison indicates that 90% of the samples collected in
the range 0.5 to 2.0 times the permissible limit have an accuracy range
of plus or minus 25 percent of the ORM results at a 95% confidence level
as demonstrated by a statistically valid protocol; and
(C) The equivalent method is documented and the results of the
comparison testing are maintained.
(iv) To satisfy the monitoring requirements of paragraph (d) of this
section, employers must use the results of monitoring analysis performed
by laboratories which have instituted quality assurance programs that
include the elements as prescribed in Appendix A of this section.
(7) Employee notification of monitoring results. (i) The employer
must, within 15 working days after the receipt of the results of any
monitoring performed under this sections, notify each affected employee
of these results either individually in writing or by posting the
results in an appropriate location that is accessible to affected
employees.
(ii) The written notification required by paragraph (d)(7)(i) of
this section shall contain the corrective action being taken by the
employer to reduce employee exposure to or below the TWA and/or
excursion limit, wherever monitoring results indicated that the TWA and/
or excursion limit had been exceeded.
(e) Regulated Areas--(1) Establishment. The employer shall establish
regulated areas wherever airborne concentrations of asbestos and/or PACM
are in excess of the TWA and/or excursion limit prescribed in paragraph
(c) of this section.
(2) Demarcation. Regulated areas shall be demarcated from the rest
of the workplace in any manner that minimizes the number of persons who
will be exposed to asbestos.
(3) Access. Access to regulated areas shall be limited to authorized
persons or to persons authorized by the Act or regulations issued
pursuant thereto.
(4) Provision of respirators. Each person entering a regulated area
shall be
[[Page 22]]
supplied with and required to use a respirator, selected in accordance
with paragraph (g)(2) of this section.
(5) Prohibited activities. The employer shall ensure that employees
do not eat, drink, smoke, chew tobacco or gum, or apply cosmetics in the
regulated areas.
(f) Methods of compliance--(1) Engineering controls and work
practices. (i) The employer shall institute engineering controls and
work practices to reduce and maintain employee exposure to or below the
TWA and/or excursion limit prescribed in paragraph (c) of this section,
except to the extent that such controls are not feasible.
(ii) Wherever the feasible engineering controls and work practices
that can be instituted are not sufficient to reduce employee exposure to
or below the TWA and/or excursion limit prescribed in paragraph (c) of
this section, the employer shall use them to reduce employee exposure to
the lowest levels achievable by these controls and shall supplement them
by the use of respiratory protection that complies with the requirements
of paragraph (g) of this section.
(iii) For the following operations, wherever feasible engineering
controls and work practices that can be instituted are not sufficient to
reduce the employee exposure to or below the TWA and/or excursion limit
prescribed in paragraph (c) of this section, the employer shall use them
to reduce employee exposure to or below 0.5 fiber per cubic centimeter
of air (as an eight-hour time-weighted average) or 2.5 fibers/cc for 30
minutes (short-term exposure) and shall supplement them by the use of
any combination of respiratory protection that complies with the
requirements of paragraph (g) of this section, work practices and
feasible engineering controls that will reduce employee exposure to or
below the TWA and to or below the excursion limit permissible prescribed
in paragraph (c) of this section: Coupling cutoff in primary asbestos
cement pipe manufacturing; sanding in primary and secondary asbestos
cement sheet manufacturing; grinding in primary and secondary friction
product manufacturing; carding and spinning in dry textile processes;
and grinding and sanding in primary plastics manufacturing.
(iv) Local exhaust ventilation. Local exhaust ventilation and dust
collection systems shall be designed, constructed, installed, and
maintained in accordance with good practices such as those found in the
American National Standard Fundamentals Governing the Design and
Operation of Local Exhaust Systems, ANSI Z9.2-1979.
(v) Particular tools. All hand-operated and power-operated tools
which would produce or release fibers of asbestos, such as, but not
limited to, saws, scorers, abrasive wheels, and drills, shall be
provided with local exhaust ventilation systems which comply with
paragraph (f)(1)(iv) of this section.
(vi) Wet methods. Insofar as practicable, asbestos shall be handled,
mixed, applied, removed, cut, scored, or otherwise worked in a wet state
sufficient to prevent the emission of airborne fibers so as to expose
employees to levels in excess of the TWA and/or excursion limit,
prescribed in paragraph (c) of this section, unless the usefulness of
the product would be diminished thereby.
(vii) [Reserved]
(viii) Particular products and operations. No asbestos cement,
mortar, coating, grout, plaster, or similar material containing
asbestos, shall be removed from bags, cartons, or other containers in
which they are shipped, without being either wetted, or enclosed, or
ventilated so as to prevent effectively the release of airborne fibers.
(ix) Compressed air. Compressed air shall not be used to remove
asbestos or materials containing asbestos unless the compressed air is
used in conjunction with a ventilation system which effectively captures
the dust cloud created by the compressed air.
(x) Flooring. Sanding of asbestos-containing flooring material is
prohibited.
(2) Compliance program. (i) Where the TWA and/or excursion limit is
exceeded, the employer shall establish and implement a written program
to reduce employee exposure to or below the TWA and to or below the
excursion limit by means of engineering and work practice controls as
required by paragraph (f)(1) of this section, and by the use of
respiratory protection where
[[Page 23]]
required or permitted under this section.
(ii) Such programs shall be reviewed and updated as necessary to
reflect significant changes in the status of the employer's compliance
program.
(iii) Written programs shall be submitted upon request for
examination and copying to the Assistant Secretary, the Director,
affected employees and designated employee representatives.
(iv) The employer shall not use employee rotation as a means of
compliance with the TWA and/or excursion limit.
(3) Specific compliance methods for brake and clutch repair:
(i) Engineering controls and work practices for brake and clutch
repair and service. During automotive brake and clutch inspection,
disassembly, repair and assembly operations, the employer shall
institute engineering controls and work practices to reduce employee
exposure to materials containing asbestos using a negative pressure
enclosure/HEPA vacuum system method or low pressure/wet cleaning method,
which meets the detailed requirements set out in Appendix F to this
section. The employer may also comply using an equivalent method which
follows written procedures which the employer demonstrates can achieve
results equivalent to Method A in Appendix F to this section. For
facilities in which no more than 5 pair of brakes or 5 clutches are
inspected, disassembled, repaired, or assembled per week, the method set
forth in paragraph [D] of Appendix F to this section may be used.
(ii) The employer may also comply by using an equivalent method
which follows written procedures, which the employer demonstrates can
achieve equivalent exposure reductions as do the two ``preferred
methods.'' Such demonstration must include monitoring data conducted
under workplace conditions closely resembling the process, type of
asbestos containing materials, control method, work practices and
environmental conditions which the equivalent method will be used, or
objective data, which document that under all reasonably foreseeable
conditions of brake and clutch repair applications, the method results
in exposures which are equivalent to the methods set out in Appendix F
to this section.
(g) Respiratory protection--(1) General. For employees who use
respirators required by this section, the employer must provide
respirators that comply with the requirements of this paragraph.
Respirators must be used during:
(i) Periods necessary to install or implement feasible engineering
and work-practice controls.
(ii) Work operations, such as maintenance and repair activities, for
which engineering and work-practice controls are not feasible.
(iii) Work operations for which feasible engineering and work-
practice controls are not yet sufficient to reduce employee exposure to
or below the TWA and/or excursion limit.
(iv) Emergencies.
(2) Respirator program. (i) The employer must implement a
respiratory protection program in accordance with 29 CFR 1910.134 (b)
through (d) (except (d)(1)(iii)), and (f) through (m).
(ii) The employer must provide a tight-fitting, powered, air-
purifying respirator instead of any negative-pressure respirator
specified in Table 1 of this section when an employee chooses to use
this type of respirator and the respirator provides adequate protection
to the employee.
(iii) No employee must be assigned to tasks requiring the use of
respirators if, based on their most recent medical examination, the
examining physician determines that the employee will be unable to
function normally using a respirator, or that the safety or health of
the employee or other employees will be impaired by the use of a
respirator. Such employees must be assigned to another job or given the
opportunity to transfer to a different position, the duties of which
they can perform. If such a transfer position is available, the position
must be with the same employer, in the same geographical area, and with
the same seniority, status, and rate of pay the employee had just prior
to such transfer.
[[Page 24]]
(3) Respirator selection. The employer must select and provide the
appropriate respirator from Table 1 of this section.
Table 1--Respiratory Protection for Asbestos Fibers
------------------------------------------------------------------------
Airborne concentration of
asbestos or conditions of use Required respirator
------------------------------------------------------------------------
Not in excess of 1 f/cc (10 X Half-mask air purifying respirator other
PEL). than a disposable respirator, equipped
with high efficiency filters.
Not in excess of 5 f/cc (50 X Full facepiece air-purifying respirator
PEL). equipped with high efficiency filters.
Not in excess of 10 f/cc (100 Any powered air-purifying respirator
X PEL). equipped with high efficiency filters or
any supplied air respirator operated in
continuous flow mode.
Not in excess of 100 f/cc Full facepiece supplied air respirator
(1,000 X PEL). operated in pressure demand mode.
Greater than 100 f/cc (1,000 Full facepiece supplied air respirator
X PEL) or unknown operated in pressure demand mode,
concentration. equipped with an auxiliary positive
pressure self-contained breathing
apparatus.
------------------------------------------------------------------------
Note: a. Respirators assigned for high environmental concentrations may
be used at lower concentrations, or when required respirator use is
independent of concentration.
b. A high efficiency filter means a filter that is at least 99.97
percent efficient against mono-dispersed particles of 0.3 micrometers
in diameter or larger.
(h) Protective work clothing and equipment--(1) Provision and use.
If an employee is exposed to asbestos above the TWA and/or excursion
limit, or where the possibility of eye irritation exists, the employer
shall provide at no cost to the employee and ensure that the employee
uses appropriate protective work clothing and equipment such as, but not
limited to:
(i) Coveralls or similar full-body work clothing;
(ii) Gloves, head coverings, and foot coverings; and
(iii) Face shields, vented goggles, or other appropriate protective
equipment which complies with 1910.133 of this Part.
(2) Removal and storage. (i) The employer shall ensure that
employees remove work clothing contaminated with asbestos only in change
rooms provided in accordance with paragraph (i)(1) of this section.
(ii) The employer shall ensure that no employee takes contaminated
work clothing out of the change room, except those employees authorized
to do so for the purpose of laundering, maintenance, or disposal.
(iii) Contaminated work clothing shall be placed and stored in
closed containers which prevent dispersion of the asbestos outside the
container.
(iv) Containers of contaminated protective devices or work clothing
which are to be taken out of change rooms or the workplace for cleaning,
maintenance or disposal, shall bear labels in accordance with paragraph
(j)(4) of this section.
(3) Cleaning and replacement. (i) The employer shall clean, launder,
repair, or replace protective clothing and equipment required by this
paragraph to maintain their effectiveness. The employer shall provide
clean protective clothing and equipment at least weekly to each affected
employee.
(ii) The employer shall prohibit the removal of asbestos from
protective clothing and equipment by blowing or shaking. (iii)
Laundering of contaminated clothing shall be done so as to prevent the
release of airborne fibers of asbestos in excess of the permissible
exposure limits prescribed in paragraph (c) of this section.
(iv) Any employer who gives contaminated clothing to another person
for laundering shall inform such person of the requirement in paragraph
(h)(3)(iii) of this section to effectively prevent the release of
airborne fibers of asbestos in excess of the permissible exposure
limits.
(v) The employer shall inform any person who launders or cleans
protective clothing or equipment contaminated with asbestos of the
potentially harmful effects of exposure to asbestos.
(vi) Contaminated clothing shall be transported in sealed
impermeable bags, or other closed, impermeable containers, and labeled
in accordance with paragraph (j) of this section.
(i) Hygiene facilities and practices--(1) Change rooms. (i) The
employer shall provide clean change rooms for employees who work in
areas where their airborne exposure to asbestos is above the TWA and/or
excursion limit.
[[Page 25]]
(ii) The employer shall ensure that change rooms are in accordance
with 1910.141(e) of this part, and are equipped with two separate
lockers or storage facilities, so separated as to prevent contamination
of the employee's street clothes from his protective work clothing and
equipment.
(2) Showers. (i) The employer shall ensure that employees who work
in areas where their airborne exposure is above the TWA and/or excursion
limit, shower at the end of the work shift.
(ii) The employer shall provide shower facilities which comply with
1910.141(d)(3) of this part.
(iii) The employer shall ensure that employees who are required to
shower pursuant to paragraph (i)(2)(i) of this section do not leave the
workplace wearing any clothing or equipment worn during the work shift.
(3) Lunchrooms. (i) The employer shall provide lunchroom facilities
for employees who work in areas where their airborne exposure is above
the TWA and/or excursion limit.
(ii) The employer shall ensure that lunchroom facilities have a
positive pressure, filtered air supply, and are readily accessible to
employees.
(iii) The employer shall ensure that employees who work in areas
where their airborne exposure is above the PEL and/or excursion limit
wash their hands and faces prior to eating, drinking or smoking.
(iv) The employer shall ensure that employees do not enter lunchroom
facilities with protective work clothing or equipment unless surface
asbestos fibers have been removed from the clothing or equipment by
vacuuming or other method that removes dust without causing the asbestos
to become airborne.
(4) Smoking in work areas. The employer shall ensure that employees
do not smoke in work areas where they are occupationally exposed to
asbestos because of activities in that work area.
(j) Communication of hazards to employees--Introduction. This
section applies to the communication of information concerning asbestos
hazards in general industry to facilitate compliance with this standard.
Asbestos exposure in general industry occurs in a wide variety of
industrial and commercial settings. Employees who manufacture asbestos-
containing products may be exposed to asbestos fibers. Employees who
repair and replace automotive brakes and clutches may be exposed to
asbestos fibers. In addition, employees engaged in housekeeping
activities in industrial facilities with asbestos product manufacturing
operations, and in public and commercial buildings with installed
asbestos containing materials may be exposed to asbestos fibers. Most of
these workers are covered by this general industry standard, with the
exception of state or local governmental employees in non-state plan
states. It should be noted that employees who perform housekeeping
activities during and after construction activities are covered by the
asbestos construction standard, 29 CFR 1926.1101, formerly 1926.58.
However, housekeeping employees, regardless of industry designation,
should know whether building components they maintain may expose them to
asbestos. The same hazard communication provisions will protect
employees who perform housekeeping operations in all three asbestos
standards; general industry, construction, and shipyard employment. As
noted in the construction standard, building owners are often the only
and/or best source of information concerning the presence of previously
installed asbestos containing building materials. Therefore they, along
with employers of potentially exposed employees, are assigned specific
information conveying and retention duties under this section.
(1) Installed Asbestos Containing Material. Employers and building
owners are required to treat installed TSI and sprayed on and troweled-
on surfacing materials as ACM in buildings constructed no later than
1980 for purposes of this standard. These materials are designated
``presumed ACM or PACM'', and are defined in paragraph (b) of this
section. Asphalt and vinyl flooring material installed no later than
1980 also must be treated as asbestos-containing. The employer or
building owner may demonstrate that PACM and flooring material do not
contain asbestos by complying with paragraph (j)(8)(iii) of this
section.
[[Page 26]]
(2) Duties of employers and building and facility owners. (i)
Building and facility owners shall determine the presence, location, and
quantity of ACM and/or PACM at the work site. Employers and building and
facility owners shall exercise due diligence in complying with these
requirements to inform employers and employees about the presence and
location of ACM and PACM.
(ii) Building and facility owners shall maintain records of all
information required to be provided pursuant to this section and/or
otherwise known to the building owner concerning the presence, location
and quantity of ACM and PACM in the building/facility. Such records
shall be kept for the duration of ownership and shall be transferred to
successive owners.
(iii) Building and facility owners shall inform employers of
employees, and employers shall inform employees who will perform
housekeeping activities in areas which contain ACM and/or PACM of the
presence and location of ACM and/or PACM in such areas which may be
contacted during such activities.
(3) Warning signs--(i) Posting. Warning signs shall be provided and
displayed at each regulated area. In addition, warning signs shall be
posted at all approaches to regulated areas so that an employee may read
the signs and take necessary protective steps before entering the area.
(ii) Sign specifications. (A) The warning signs required by
paragraph (j)(3) of this section shall bear the following information:
DANGER
ASBESTOS
CANCER AND LUNG DISEASE HAZARD
AUTHORIZED PERSONNEL ONLY
(B) In addition, where the use of respirators and protective
clothing is required in the regulated area under this section, the
warning signs shall include the following:
RESPIRATORS AND PROTECTIVE CLOTHING
ARE REQUIRED IN THIS AREA
(iii) [Reserved]
(iv) The employer shall ensure that employees working in and
contiguous to regulated areas comprehend the warning signs required to
be posted by paragraph (j)(3)(i) of this section. Means to ensure
employee comprehension may include the use of foreign languages,
pictographs and graphics.
(v) At the entrance to mechanical rooms/areas in which employees
reasonably can be expected to enter and which contain ACM and/or PACM,
the building owner shall post signs which identify the material which is
present, its location, and appropriate work practices which, if
followed, will ensure that ACM and/or PACM will not be disturbed. The
employer shall ensure, to the extent feasible, that employees who come
in contact with these signs can comprehend them. Means to ensure
employee comprehension may include the use of foreign languages,
pictographs, graphics, and awareness training.
(4) Warning labels--(i) Labeling. Warning labels shall be affixed to
all raw materials, mixtures, scrap, waste, debris, and other products
containing asbestos fibers, or to their containers.When a building owner
or employer identifies previously installed ACM and/or PACM, labels or
signs shall be affixed or posted so that employees will be notified of
what materials contain ACM and/or PACM. The employer shall attach such
labels in areas where they will clearly be noticed by employees who are
likely to be exposed, such as at the entrance to mechanical room/areas.
Signs required by paragraph (j)(3) of this section may be posted in lieu
of labels so long as they contain information required for labelling.
(ii) Label specifications. The labels shall comply with the
requirements of 29 CFR 1910.1200(f) of OSHA's Hazard Communication
standard, and shall include the following information:
DANGER
CONTAINS ASBESTOS FIBERS
AVOID CREATING DUST
CANCER AND LUNG DISEASE HAZARD
(5) Material safety data sheets. Employers who are manufacturers or
importers of asbestos or asbestos products shall comply with the
requirements regarding development of material safety data sheets as
specified in 29 CFR 1910.1200(g) of OSHA's Hazard Communication
standard, except as provided by paragraph (j)(6) of this section.
[[Page 27]]
(6) The provisions for labels required by paragraph (j)(4) of this
section or for material safety data sheets required by paragraph (j)(5)
of this section do not apply where:
(i) Asbestos fibers have been modified by a bonding agent, coating,
binder, or other material provided that the manufacturer can demonstrate
that during any reasonably foreseeable use, handling, storage, disposal,
processing, or transportation, no airborne concentrations of fibers of
asbestos in excess of the TWA permissible exposure level and/or
excursion limit will be released or
(ii) Asbestos is present in a product in concentrations less than
1.0%.
(7) Employee information and training. (i) The employer shall
institute a training program for all employees who are exposed to
airborne concentrations of asbestos at or above the PEL and/or excursion
limit and ensure their participation in the program.
(ii) Training shall be provided prior to or at the time of initial
assignment and at least annually thereafter.
(iii) The training program shall be conducted in a manner which the
employee is able to understand. The employer shall ensure that each
employee is informed of the following:
(A) The health effects associated with asbestos exposure;
(B) The relationship between smoking and exposure to asbestos
producing lung cancer:
(C) The quantity, location, manner of use, release, and storage of
asbestos, and the specific nature of operations which could result in
exposure to asbestos;
(D) The engineering controls and work practices associated with the
employee's job assignment;
(E) The specific procedures implemented to protect employees from
exposure to asbestos, such as appropriate work practices, emergency and
clean-up procedures, and personal protective equipment to be used;
(F) The purpose, proper use, and limitations of respirators and
protective clothing, if appropriate;
(G) The purpose and a description of the medical surveillance
program required by paragraph (l) of this section;
(H) The content of this standard, including appendices.
(I) The names, addresses and phone numbers of public health
organizations which provide information, materials, and/or conduct
programs concerning smoking cessation. The employer may distribute the
list of such organizations contained in Appendix I to this section, to
comply with this requirement.
(J) The requirements for posting signs and affixing labels and the
meaning of the required legends for such signs and labels.
(iv) The employer shall also provide, at no cost to employees who
perform housekeeping operations in an area which contains ACM or PACM,
an asbestos awareness training course, which shall at a minimum contain
the following elements: health effects of asbestos, locations of ACM and
PACM in the building/facility, recognition of ACM and PACM damage and
deterioration, requirements in this standard relating to housekeeping,
and proper response to fiber release episodes, to all employees who
perform housekeeping work in areas where ACM and/or PACM is present.
Each such employee shall be so trained at least once a year.
(v) Access to information and training materials.
(A) The employer shall make a copy of this standard and its
appendices readily available without cost to all affected employees.
(B) The employer shall provide, upon request, all materials relating
to the employee information and training program to the Assistant
Secretary and the training program to the Assistant Secretary and the
Director.
(C) The employer shall inform all employees concerning the
availability of self-help smoking cessation program material. Upon
employee request, the employer shall distribute such material,
consisting of NIH Publication No. 89-1647, or equivalent self-help
material, which is approved or published by a public health organization
listed in Appendix I to this section.
(8) Criteria to rebut the designation of installed material as PACM.
(i) At any time, an employer and/or building owner may demonstrate, for
purposes of this standard, that PACM does not
[[Page 28]]
contain asbestos. Building owners and/or employers are not required to
communicate information about the presence of building material for
which such a demonstration pursuant to the requirements of paragraph
(j)(8)(ii) of this section has been made. However, in all such cases,
the information, data and analysis supporting the determination that
PACM does not contain asbestos, shall be retained pursuant to paragraph
(m) of this section.
(ii) An employer or owner may demonstrate that PACM does not contain
asbestos by the following:
(A) Having a completed inspection conducted pursuant to the
requirements of AHERA (40 CFR 763, Subpart E) which demonstrates that no
ACM is present in the material; or
(B) Performing tests of the material containing PACM which
demonstrate that no ACM is present in the material. Such tests shall
include analysis of bulk samples collected in the manner described in 40
CFR 763.86. The tests, evaluation and sample collection shall be
conducted by an accredited inspector or by a CIH. Analysis of samples
shall be performed by persons or laboratories with proficiency
demonstrated by current successful participation in a nationally
recognized testing program such as the National Voluntary Laboratory
Accreditation Program (NVLAP) or the National Institute for Standards
and Technology (NIST) or the Round Robin for bulk samples administered
by the American Industrial Hygiene Association (AIHA) or an equivalent
nationally-recognized round robin testing program.
(iii) The employer and/or building owner may demonstrate that
flooring material including associated mastic and backing does not
contain asbestos, by a determination of an industrial hygienist based
upon recognized analytical techniques showing that the material is not
ACM.
(k) Housekeeping. (1) All surfaces shall be maintained as free as
practicable of ACM waste and debris and accompanying dust.
(2) All spills and sudden releases of material containing asbestos
shall be cleaned up as soon as possible.
(3) Surfaces contaminated with asbestos may not be cleaned by the
use of compressed air.
(4) Vacuuming. HEPA-filtered vacuuming equipment shall be used for
vacuuming asbestos containing waste and debris. The equipment shall be
used and emptied in a manner which minimizes the reentry of asbestos
into the workplace.
(5) Shoveling, dry sweeping and dry clean-up of asbestos may be used
only where vacuuming and/or wet cleaning are not feasible.
(6) Waste disposal. Waste, scrap, debris, bags, containers,
equipment, and clothing contaminated with asbestos consigned for
disposal, shall be collected, recycled and disposed of in sealed
impermeable bags, or other closed, impermeable containers.
(7) Care of asbestos-containing flooring material.
(i) Sanding of asbestos-containing floor material is prohibited.
(ii) Stripping of finishes shall be conducted using low abrasion
pads at speeds lower than 300 rpm and wet methods.
(iii) Burnishing or dry buffing may be performed only on asbestos-
containing flooring which has sufficient finish so that the pad cannot
contact the asbestos-containing material.
(8) Waste and debris and accompanying dust in an area containing
accessible ACM and/or PACM or visibly deteriorated ACM, shall not be
dusted or swept dry, or vacuumed without using a HEPA filter.
(l) Medical surveillance--(1) General--(i) Employees covered. The
employer shall institute a medical surveillance program for all
employees who are or will be exposed to airborne concentrations of
fibers of asbestos at or above the TWA and/or excursion limit.
(ii) Examination by a physician. (A) The employer shall ensure that
all medical examinations and procedures are performed by or under the
supervision of a licensed physician, and shall be provided without cost
to the employee and at a reasonable time and place.
(B) Persons other than licensed physicians, who administer the
pulmonary function testing required by this section, shall complete a
training course
[[Page 29]]
in spirometry sponsored by an appropriate academic or professional
institution.
(2) Pre-placement examinations. (i) Before an employee is assigned
to an occupation exposed to airborne concentrations of asbestos fibers
at or above the TWA and/or excursion limit, a pre-placement medical
examination shall be provided or made available by the employer.
(ii) Such examination shall include, as a minimum, a medical and
work history; a complete physical examination of all systems with
emphasis on the respiratory system, the cardiovascular system and
digestive tract; completion of the respiratory disease standardized
questionnaire in Appendix D to this section, Part 1; a chest
roentgenogram (posterior-anterior 14x17 inches); pulmonary function
tests to include forced vital capacity (FVC) and forced expiratory
volume at 1 second (FEV(1.0)); and any additional tests deemed
appropriate by the examining physician. Interpretation and
classification of chest roentgenogram shall be conducted in accordance
with Appendix E to this section.
(3) Periodic examinations. (i) Periodic medical examinations shall
be made available annually.
(ii) The scope of the medical examination shall be in conformance
with the protocol established in paragraph (l)(2)(ii) of this section,
except that the frequency of chest roentgenogram shall be conducted in
accordance with Table 2, and the abbreviated standardized questionnaire
contained in, Part 2 of Appendix D to this section shall be administered
to the employee.
Table 2--Frequency of Chest Roentgenogram
----------------------------------------------------------------------------------------------------------------
Age of employee
Years since first exposure --------------------------------------------------------------------------------
15 to 35 35+ to 45 45+
----------------------------------------------------------------------------------------------------------------
0 to 10........................ Every 5 years.............. Every 5 years............. Every 5 years.
10+............................ Every 5 years.............. Every 2 years............. Every 1 year.
----------------------------------------------------------------------------------------------------------------
(4) Termination of employment examinations. (i) The employer shall
provide, or make available, a termination of employment medical
examination for any employee who has been exposed to airborne
concentrations of fibers of asbestos at or above the TWA and/or
excursion limit.
(ii) The medical examination shall be in accordance with the
requirements of the periodic examinations stipulated in paragraph (l)(3)
of this section, and shall be given within 30 calendar days before or
after the date of termination of employment.
(5) Recent examinations. No medical examination is required of any
employee, if adequate records show that the employee has been examined
in accordance with any of paragraphs ((l)(2) through (l)(4)) of this
section within the past 1 year period. A pre- employment medical
examination which was required as a condition of employment by the
employer, may not be used by that employer to meet the requirements of
this paragraph, unless the cost of such examination is borne by the
employer.
(6) Information provided to the physician. The employer shall
provide the following information to the examining physician:
(i) A copy of this standard and Appendices D and E.
(ii) A description of the affected employee's duties as they relate
to the employee's exposure.
(iii) The employee's representative exposure level or anticipated
exposure level.
(iv) A description of any personal protective and respiratory
equipment used or to be used.
(v) Information from previous medical examinations of the affected
employee that is not otherwise available to the examining physician.
(7) Physician's written opinion. (i) The employer shall obtain a
written opinion from the examining physician. This written opinion shall
contain the results of the medical examination and shall include:
[[Page 30]]
(A) The physician's opinion as to whether the employee has any
detected medical conditions that would place the employee at an
increased risk of material health impairment from exposure to asbestos;
(B) Any recommended limitations on the employee or upon the use of
personal protective equipment such as clothing or respirators;
(C) A statement that the employee has been informed by the physician
of the results of the medical examination and of any medical conditions
resulting from asbestos exposure that require further explanation or
treatment; and
(D) A statement that the employee has been informed by the physician
of the increased risk of lung cancer attributable to the combined effect
of smoking and asbestos exposure.
(ii) The employer shall instruct the physician not to reveal in the
written opinion given to the employer specific findings or diagnoses
unrelated to occupational exposure to asbestos.
(iii) The employer shall provide a copy of the physician's written
opinion to the affected employee within 30 days from its receipt.
(m) Recordkeeping--(1) Exposure measurements.
Note: The employer may utilize the services of competent
organizations such as industry trade associations and employee
associations to maintain the records required by this section.
(i) The employer shall keep an accurate record of all measurements
taken to monitor employee exposure to asbestos as prescribed in
paragraph (d) of this section.
(ii) This record shall include at least the following information:
(A) The date of measurement;
(B) The operation involving exposure to asbestos which is being
monitored;
(C) Sampling and analytical methods used and evidence of their
accuracy;
(D) Number, duration, and results of samples taken;
(E) Type of respiratory protective devices worn, if any; and
(F) Name, social security number and exposure of the employees whose
exposure are represented.
(iii) The employer shall maintain this record for at least thirty
(30) years, in accordance with 29 CFR 1910.20.
(2) Objective data for exempted operations. (i) Where the
processing, use, or handling of products made from or containing
asbestos is exempted from other requirements of this section under
paragraph (d)(2)(iii) of this section, the employer shall establish and
maintain an accurate record of objective data reasonably relied upon in
support of the exemption.
(ii) The record shall include at least the following:
(A) The product qualifying for exemption;
(B) The source of the objective data;
(C) The testing protocol, results of testing, and/or analysis of the
material for the release of asbestos;
(D) A description of the operation exempted and how the data support
the exemption; and
(E) Other data relevant to the operations, materials, processing, or
employee exposures covered by the exemption.
(iii) The employer shall maintain this record for the duration of
the employer's reliance upon such objective data.
(3) Medical surveillance. (i) The employer shall establish and
maintain an accurate record for each employee subject to medical
surveillance by paragraph (l)(1)(i) of this section, in accordance with
29 CFR 1910.1020.
(ii) The record shall include at least the following information:
(A) The name and social security number of the employee;
(B) Physician's written opinions;
(C) Any employee medical complaints related to exposure to asbestos;
and
(D) A copy of the information provided to the physician as required
by paragraph (l)(6) of this section.
(iii) The employer shall ensure that this record is maintained for
the duration of employment plus thirty (30) years, in accordance with 29
CFR 1910.1020.
(4) Training. The employer shall maintain all employee training
records for one (1) year beyond the last date of employment of that
employee.
(5) Availability. (i) The employer, upon written request, shall make
all
[[Page 31]]
records required to be maintained by this section available to the
Assistant Secretary and the Director for examination and copying.
(ii) The employer, upon request shall make any exposure records
required by paragraph (m)(1) of this section available for examination
and copying to affected employees, former employees, designated
representatives and the Assistant Secretary, in accordance with 29 CFR
1910.1020 (a) through (e) and (g) through (i).
(iii) The employer, upon request, shall make employee medical
records required by paragraph (m)(3) of this section available for
examination and copying to the subject employee, to anyone having the
specific written consent of the subject employee, and the Assistant
Secretary, in accordance with 29 CFR 1910.1020.
(6) Transfer of records. (i) The employer shall comply with the
requirements concerning transfer of records set forth in 29 CFR
1910.1020(h).
(ii) Whenever the employer ceases to do business and there is no
successor employer to receive and retain the records for the prescribed
period, the employer shall notify the Director at least 90 days prior to
disposal of records and, upon request, transmit them to the Director.
(n) Observation of monitoring--(1) Employee observation. The
employer shall provide affected employees or their designated
representatives an opportunity to observe any monitoring of employee
exposure to asbestos conducted in accordance with paragraph (d) of this
section.
(2) Observation procedures. When observation of the monitoring of
employee exposure to asbestos requires entry into an area where the use
of protective clothing or equipment is required, the observer shall be
provided with and be required to use such clothing and equipment and
shall comply with all other applicable safety and health procedures.
(o) Appendices. (1) Appendices A, C, D, E, and F to this section are
incorporated as part of this section and the contents of these
Appendices are mandatory.
(2) Appendices B, G, H, I, and J to this section are informational
and are not intended to create any additional obligations not otherwise
imposed or to detract from any existing obligations.
Appendix A to Sec. 1910.1001--OSHA Reference Method--Mandatory
This mandatory appendix specifies the procedure for analyzing air
samples for asbestos and specifies quality control procedures that must
be implemented by laboratories performing the analysis. The sampling and
analytical methods described below represent the elements of the
available monitoring methods (such as Appendix B of their regulation,
the most current version of the OSHA method ID-160, or the most current
version of the NIOSH Method 7400). All employers who are required to
conduct air monitoring under paragraph (d) of the standard are required
to utilize analytical laboratories that use this procedure, or an
equivalent method, for collecting and analyzing samples.
Sampling and Analytical Procedure
1. The sampling medium for air samples shall be mixed cellulose
ester filter membranes. These shall be designated by the manufacturer as
suitable for asbestos counting. See below for rejection of blanks.
2. The preferred collection device shall be the 25-mm diameter
cassette with an open-faced 50-mm electrically conductive extension
cowl. The 37-mm cassette may be used if necessary but only if written
justification for the need to use the 37-mm filter cassette accompanies
the sample results in the employee's exposure monitoring record. Do not
reuse or reload cassettes for asbestos sample collection.
3. An air flow rate between 0.5 liter/min and 2.5 liters/min shall
be selected for the 25-mm cassette. If the 37-mm cassette is used, an
air flow rate between 1 liter/min and 2.5 liters/min shall be selected.
4. Where possible, a sufficient air volume for each air sample shall
be collected to yield between 100 and 1,300 fibers per square millimeter
on the membrane filter. If a filter darkens in appearance or if loose
dust is seen on the filter, a second sample shall be started.
5. Ship the samples in a rigid container with sufficient packing
material to prevent dislodging the collected fibers. Packing material
that has a high electrostatic charge on its surface (e.g., expanded
polystyrene) cannot be used because such material can cause loss of
fibers to the sides of the cassette.
6. Calibrate each personal sampling pump before and after use with a
representative filter cassette installed between the pump and the
calibration devices.
[[Page 32]]
7. Personal samples shall be taken in the ``breathing zone'' of the
employee (i.e., attached to or near the collar or lapel near the
worker's face).
8. Fiber counts shall be made by positive phase contrast using a
microscope with an 8 to 10 X eyepiece and a 40 to 45 X objective for a
total magnification of approximately 400 X and a numerical aperture of
0.65 to 0.75. The microscope shall also be fitted with a green or blue
filter.
9. The microscope shall be fitted with a Walton-Beckett eyepiece
graticule calibrated for a field diameter of 100 micrometers (2 micrometers).
10. The phase-shift detection limit of the microscope shall be about
3 degrees measured using the HSE phase shift test slide as outlined
below.
a. Place the test slide on the microscope stage and center it under
the phase objective.
b. Bring the blocks of grooved lines into focus.
Note: The slide consists of seven sets of grooved lines (ca. 20
grooves to each block) in descending order of visibility from sets 1 to
7, seven being the least visible. The requirements for asbestos counting
are that the microscope optics must resolve the grooved lines in set 3
completely, although they may appear somewhat faint, and that the
grooved lines in sets 6 and 7 must be invisible. Sets 4 and 5 must be at
least partially visible but may vary slightly in visibility between
microscopes. A microscope that fails to meet these requirements has
either too low or too high a resolution to be used for asbestos
counting.
c. If the image deteriorates, clean and adjust the microscope
optics. If the problem persists, consult the microscope manufacturer.
11. Each set of samples taken will include 10% field blanks or a
minimum of 2 field blanks. These blanks must come from the same lot as
the filters used for sample collection. The field blank results shall be
averaged and subtracted from the analytical results before reporting. A
set consists of any sample or group of samples for which an evaluation
for this standard must be made. Any samples represented by a field blank
having a fiber count in excess of the detection limit of the method
being used shall be rejected.
12. The samples shall be mounted by the acetone/triacetin method or
a method with an equivalent index of refraction and similar clarity.
13. Observe the following counting rules.
a. Count only fibers equal to or longer than 5 micrometers. Measure
the length of curved fibers along the curve.
b. In the absence of other information, count all particles as
asbesto that have a length-to-width ratio (aspect ratio) of 3:1 or
greater.
c. Fibers lying entirely within the boundary of the Walton-Beckett
graticule field shall receive a count of 1. Fibers crossing the boundary
once, having one end within the circle, shall receive the count of one
half (\1/2\). Do not count any fiber that crosses the graticule boundary
more than once. Reject and do not count any other fibers even though
they may be visible outside the graticule area.
d. Count bundles of fibers as one fiber unless individual fibers can
be identified by observing both ends of an individual fiber.
e. Count enough graticule fields to yield 100 fibers. Count a
minimum of 20 fields; stop counting at 100 fields regardless of fiber
count.
14. Blind recounts shall be conducted at the rate of 10 percent.
Quality Control Procedures
1. Intralaboratory program. Each laboratory and/or each company with
more than one microscopist counting slides shall establish a
statistically designed quality assurance program involving blind
recounts and comparisons between microscopists to monitor the
variability of counting by each microscopist and between microscopists.
In a company with more than one laboratory, the program shall include
all laboratories and shall also evaluate the laboratory-to-laboratory
variability.
2.a. Interlaboratory program. Each laboratory analyzing asbestos
samples for compliance determination shall implement an interlaboratory
quality assurance program that as a minimum includes participation of at
least two other independent laboratories. Each laboratory shall
participate in round robin testing at least once every 6 months with at
least all the other laboratories in its interlaboratory quality
assurance group. Each laboratory shall submit slides typical of its own
work load for use in this program. The round robin shall be designed and
results analyzed using appropriate statistical methodology.
2.b. All laboratories should also participate in a national sample
testing scheme such as the Proficiency Analytical Testing Program (PAT),
or the Asbestos Registry sponsored by the American Industrial Hygiene
Association (AIHA).
3. All individuals performing asbestos analysis must have taken the
NIOSH course for sampling and evaluating airborne asbestos dust or an
equalivalent course.
4. When the use of different microscopes contributes to differences
between counters and laboratories, the effect of the different
microscope shall be evaluated and the microscope shall be replaced, as
necessary.
[[Page 33]]
5. Current results of these quality assurance programs shall be
posted in each laboratory to keep the microscopists informed.
Appendix B to Sec. 1910.1001--Detailed Procedures for Asbestos Sampling
and Analysis--Non-mandatory
Matrix Air:
OSHA Permissible Exposure Limits:
Time Weighted Average.............. 0.1 fiber/cc
Excursion Level (30 minutes)....... 1.0 fiber/cc
Collection Procedure:
A known volume of air is drawn through a 25-mm diameter cassette
containing a mixed-cellulose ester filter. The cassette must be equipped
with an electrically conductive 50-mm extension cowl. The sampling time
and rate are chosen to give a fiber density of between 100 to 1,300
fibers/mm\2\ on the filter.
Recommended Sampling Rate.............. 0.5 to 5.0 liters/minute (L/
min)
Recommended Air Volumes:
Minimum............................ 25 L
Maximum............................ 2,400 L
------------------------------------------------------------------------
Analytical Procedure: A portion of the sample filter is cleared and
prepared for asbestos fiber counting by Phase Contrast Microscopy (PCM)
at 400X.
Commercial manufacturers and products mentioned in this method are
for descriptive use only and do not constitute endorsements by USDOL-
OSHA. Similar products from other sources can be substituted.
1. Introduction
This method describes the collection of airborne asbestos fibers
using calibrated sampling pumps with mixed-cellulose ester (MCE) filters
and analysis by phase contrast microscopy (PCM). Some terms used are
unique to this method and are defined below:
Asbestos: A term for naturally occurring fibrous minerals. Asbestos
includes chrysotile, crocidolite, amosite (cummingtonite-grunerite
asbestos), tremolite asbestos, actinolite asbestos, anthophyllite
asbestos, and any of these minerals that have been chemically treated
and/or altered. The precise chemical formulation of each species will
vary with the location from which it was mined. Nominal compositions are
listed:
Chrysotile................................ Mg3 Si2 O5(OH)4
Crocidolite............................... Na2 Fe32+ Fe23 + Si8 O22
(OH)\2\
Amosite................................... (Mg,Fe)7 Si8 O22 (OH)2
Tremolite-actinolite...................... Ca2(Mg,Fe)5 Si8 O22 (OH)2
Anthophyllite............................. (Mg,Fe)7 Si8 O22 (OH)2
Asbestos Fiber: A fiber of asbestos which meets the criteria
specified below for a fiber.
Aspect Ratio: The ratio of the length of a fiber to it's diameter
(e.g. 3:1, 5:1 aspect ratios).
Cleavage Fragments: Mineral particles formed by comminution of
minerals, especially those characterized by parallel sides and a
moderate aspect ratio (usually less than 20:1).
Detection Limit: The number of fibers necessary to be 95% certain
that the result is greater than zero.
Differential Counting: The term applied to the practice of excluding
certain kinds of fibers from the fiber count because they do not appear
to be asbestos.
Fiber: A particle that is 5 [micro]m or longer, with a length-to-
width ratio of 3 to 1 or longer.
Field: The area within the graticule circle that is superimposed on
the microscope image.
Set: The samples which are taken, submitted to the laboratory,
analyzed, and for which, interim or final result reports are generated.
Tremolite, Anthophyllite, and Actinolite: The non-asbestos form of
these minerals which meet the definition of a fiber. It includes any of
these minerals that have been chemically treated and/or altered.
Walton-Beckett Graticule: An eyepiece graticule specifically
designed for asbestos fiber counting. It consists of a circle with a
projected diameter of 100 2 [micro]m (area of about 0.00785 mm\2\) with
a crosshair having tic-marks at 3-[micro]m intervals in one direction
and 5-[micro]m in the orthogonal direction. There are marks around the
periphery of the circle to demonstrate the proper sizes and shapes of
fibers. This design is reproduced in Figure 1. The disk is placed in one
of the microscope eyepieces so that the design is superimposed on the
field of view.
1.1. History
Early surveys to determine asbestos exposures were conducted using
impinger counts of total dust with the counts expressed as million
particles per cubic foot. The British Asbestos Research Council
recommended filter membrane counting in 1969. In July 1969, the Bureau
of Occupational Safety and Health published a filter membrane method for
counting asbestos fibers in the United States. This method was refined
by NIOSH and published as P CAM 239. On May 29, 1971, OSHA specified
filter membrane sampling with phase contrast counting for evaluation of
asbestos exposures at work sites in the United States. The use of this
technique was again required by OSHA in 1986. Phase contrast microscopy
has continued to be the method of choice for the measurement of
occupational exposure to asbestos.
1.2. Principle
Air is drawn through a MCE filter to capture airborne asbestos
fibers. A wedge shaped portion of the filter is removed, placed on a
glass microscope slide and made transparent. A measured area (field) is
viewed by PCM.
[[Page 34]]
All the fibers meeting defined criteria for asbestos are counted and
considered a measure of the airborne asbestos concentration.
1.3. Advantages and Disadvantages
There are four main advantages of PCM over other methods:
(1) The technique is specific for fibers. Phase contrast is a fiber
counting technique which excludes non-fibrous particles from the
analysis.
(2) The technique is inexpensive and does not require specialized
knowledge to carry out the analysis for total fiber counts.
(3) The analysis is quick and can be performed on-site for rapid
determination of air concentrations of asbestos fibers.
(4) The technique has continuity with historical epidemiological
studies so that estimates of expected disease can be inferred from long-
term determinations of asbestos exposures.
The main disadvantage of PCM is that it does not positively identify
asbestos fibers. Other fibers which are not asbestos may be included in
the count unless differential counting is performed. This requires a
great deal of experience to adequately differentiate asbestos from non-
asbestos fibers. Positive identification of asbestos must be performed
by polarized light or electron microscopy techniques. A further
disadvantage of PCM is that the smallest visible fibers are about 0.2
[micro]m in diameter while the finest asbestos fibers may be as small as
0.02 [micro]m in diameter. For some exposures, substantially more fibers
may be present than are actually counted.
1.4. Workplace Exposure
Asbestos is used by the construction industry in such products as
shingles, floor tiles, asbestos cement, roofing felts, insulation and
acoustical products. Non-construction uses include brakes, clutch
facings, paper, paints, plastics, and fabrics. One of the most
significant exposures in the workplace is the removal and encapsulation
of asbestos in schools, public buildings, and homes. Many workers have
the potential to be exposed to asbestos during these operations.
About 95% of the asbestos in commercial use in the United States is
chrysotile. Crocidolite and amosite make up most of the remainder.
Anthophyllite and tremolite or actinolite are likely to be encountered
as contaminants in various industrial products.
1.5. Physical Properties
Asbestos fiber possesses a high tensile strength along its axis, is
chemically inert, non-combustible, and heat resistant. It has a high
electrical resistance and good sound absorbing properties. It can be
weaved into cables, fabrics or other textiles, and also matted into
asbestos papers, felts, or mats.
2. Range and Detection Limit
2.1. The ideal counting range on the filter is 100 to 1,300 fibers/
mm\2\. With a Walton-Beckett graticule this range is equivalent to 0.8
to 10 fibers/field. Using NIOSH counting statistics, a count of 0.8
fibers/field would give an approximate coefficient of variation (CV) of
0.13.
2.2. The detection limit for this method is 4.0 fibers per 100
fields or 5.5 fibers/mm\2\. This was determined using an equation to
estimate the maximum CV possible at a specific concentration (95%
confidence) and a Lower Control Limit of zero. The CV value was then
used to determine a corresponding concentration from historical CV vs
fiber relationships. As an example:
Lower Control Limit (95% Confidence) = AC - 1.645(CV)(AC)
Where:
AC = Estimate of the airborne fiber concentration (fibers/cc) Setting
the Lower Control Limit = 0 and solving for CV:
0 = AC - 1.645(CV)(AC)
CV = 0.61
This value was compared with CV vs. count curves. The count at which
CV = 0.61 for Leidel-Busch counting statistics or for an OSHA Salt Lake
Technical Center (OSHA-SLTC) CV curve (see Appendix A for further
information) was 4.4 fibers or 3.9 fibers per 100 fields, respectively.
Although a lower detection limit of 4 fibers per 100 fields is supported
by the OSHA-SLTC data, both data sets support the 4.5 fibers per 100
fields value.
3. Method Performance--Precision and Accuracy
Precision is dependent upon the total number of fibers counted and
the uniformity of the fiber distribution on the filter. A general rule
is to count at least 20 and not more than 100 fields. The count is
discontinued when 100 fibers are counted, provided that 20 fields have
already been counted. Counting more than 100 fibers results in only a
small gain in precision. As the total count drops below 10 fibers, an
accelerated loss of precision is noted.
At this time, there is no known method to determine the absolute
accuracy of the asbestos analysis. Results of samples prepared through
the Proficiency Analytical Testing (PAT) Program and analyzed by the
OSHA-SLTC showed no significant bias when compared to PAT reference
values. The PAT samples were analyzed from 1987 to 1989 (N=36) and the
concentration range was from 120 to 1,300 fibers/mm\2\.
4. Interferences
Fibrous substances, if present, may interfere with asbestos
analysis.
Some common fibers are:
fiberglass
[[Page 35]]
anhydrite
plant fibers
perlite veins
gypsum
some synthetic fibers
membrane structures
sponge spicules
diatoms
microorganisms
wollastonite
The use of electron microscopy or optical tests such as polarized
light, and dispersion staining may be used to differentiate these
materials from asbestos when necessary.
5. Sampling
5.1. Equipment
5.1.1. Sample assembly (The assembly is shown in Figure 3).
Conductive filter holder consisting of a 25-mm diameter, 3-piece
cassette having a 50-mm long electrically conductive extension cowl.
Backup pad, 25-mm, cellulose. Membrane filter, mixed-cellulose ester
(MCE), 25-mm, plain, white, 0.4 to 1.2-[micro]m pore size.
Notes: (a) Do not re-use cassettes.
(b) Fully conductive cassettes are required to reduce fiber loss to
the sides of the cassette due to electrostatic attraction.
(c) Purchase filters which have been selected by the manufacturer
for asbestos counting or analyze representative filters for fiber
background before use. Discard the filter lot if more than 4 fibers/100
fields are found.
(d) To decrease the possibility of contamination, the sampling
system (filter-backup pad-cassette) for asbestos is usually preassembled
by the manufacturer.
(e) Other cassettes, such as the Bell-mouth, may be used within the
limits of their validation.
5.1.2. Gel bands for sealing cassettes.
5.1.3. Sampling pump.
Each pump must be a battery operated, self-contained unit small
enough to be placed on the monitored employee and not interfere with the
work being performed. The pump must be capable of sampling at the
collection rate for the required sampling time.
5.1.4. Flexible tubing, 6-mm bore.
5.1.5. Pump calibration.
Stopwatch and bubble tube/burette or electronic meter.
5.2. Sampling Procedure
5.2.1. Seal the point where the base and cowl of each cassette meet
with a gel band or tape.
5.2.2. Charge the pumps completely before beginning.
5.2.3. Connect each pump to a calibration cassette with an
appropriate length of 6-mm bore plastic tubing. Do not use luer
connectors--the type of cassette specified above has built-in adapters.
5.2.4. Select an appropriate flow rate for the situation being
monitored. The sampling flow rate must be between 0.5 and 5.0 L/min for
personal sampling and is commonly set between 1 and 2 L/min. Always
choose a flow rate that will not produce overloaded filters.
5.2.5. Calibrate each sampling pump before and after sampling with a
calibration cassette in-line (Note: This calibration cassette should be
from the same lot of cassettes used for sampling). Use a primary
standard (e.g. bubble burette) to calibrate each pump. If possible,
calibrate at the sampling site.
Note: If sampling site calibration is not possible, environmental
influences may affect the flow rate. The extent is dependent on the type
of pump used. Consult with the pump manufacturer to determine dependence
on environmental influences. If the pump is affected by temperature and
pressure changes, correct the flow rate using the formula shown in the
section ``Sampling Pump Flow Rate Corrections'' at the end of this
appendix.
5.2.6. Connect each pump to the base of each sampling cassette with
flexible tubing. Remove the end cap of each cassette and take each air
sample open face. Assure that each sample cassette is held open side
down in the employee's breathing zone during sampling. The distance from
the nose/mouth of the employee to the cassette should be about 10 cm.
Secure the cassette on the collar or lapel of the employee using spring
clips or other similar devices.
5.2.7. A suggested minimum air volume when sampling to determine TWA
compliance is 25 L. For Excursion Limit (30 min sampling time)
evaluations, a minimum air volume of 48 L is recommended.
5.2.8. The most significant problem when sampling for asbestos is
overloading the filter with non-asbestos dust. Suggested maximum air
sample volumes for specific environments are:
------------------------------------------------------------------------
Environment Air vol. (L)
------------------------------------------------------------------------
Asbestos removal operations (visible dust).. 100
Asbestos removal operations (little dust)... 240
Office environments......................... 400
to
2,400
------------------------------------------------------------------------
Caution: Do not overload the filter with dust. High levels of non-
fibrous dust particles may obscure fibers on the filter and lower the
count or make counting impossible. If more than about 25 to 30% of the
field area is obscured with dust, the result may be biased low. Smaller
air volumes may be necessary when there is excessive non-asbestos dust
in the air.
While sampling, observe the filter with a small flashlight. If there
is a visible layer of dust on the filter, stop sampling, remove and seal
the cassette, and replace with a new
[[Page 36]]
sampling assembly. The total dust loading should not exceed 1 mg.
5.2.9. Blank samples are used to determine if any contamination has
occurred during sample handling. Prepare two blanks for the first 1 to
20 samples. For sets containing greater than 20 samples, prepare blanks
as 10% of the samples. Handle blank samples in the same manner as air
samples with one exception: Do not draw any air through the blank
samples. Open the blank cassette in the place where the sample cassettes
are mounted on the employee. Hold it open for about 30 seconds. Close
and seal the cassette appropriately. Store blanks for shipment with the
sample cassettes.
5.2.10. Immediately after sampling, close and seal each cassette
with the base and plastic plugs. Do not touch or puncture the filter
membrane as this will invalidate the analysis.
5.2.11 Attach and secure a sample seal around each sample cassette
in such a way as to assure that the end cap and base plugs cannot be
removed without destroying the seal. Tape the ends of the seal together
since the seal is not long enough to be wrapped end-to-end. Also wrap
tape around the cassette at each joint to keep the seal secure.
5.3. Sample Shipment
5.3.1. Send the samples to the laboratory with paperwork requesting
asbestos analysis. List any known fibrous interferences present during
sampling on the paperwork. Also, note the workplace operation(s)
sampled.
5.3.2. Secure and handle the samples in such that they will not
rattle during shipment nor be exposed to static electricity. Do not ship
samples in expanded polystyrene peanuts, vermiculite, paper shreds, or
excelsior. Tape sample cassettes to sheet bubbles and place in a
container that will cushion the samples in such a manner that they will
not rattle.
5.3.3. To avoid the possibility of sample contamination, always ship
bulk samples in separate mailing containers.
6. Analysis
6.1. Safety Precautions
6.1.1. Acetone is extremely flammable and precautions must be taken
not to ignite it. Avoid using large containers or quantities of acetone.
Transfer the solvent in a ventilated laboratory hood. Do not use acetone
near any open flame. For generation of acetone vapor, use a spark free
heat source.
6.1.2. Any asbestos spills should be cleaned up immediately to
prevent dispersal of fibers. Prudence should be exercised to avoid
contamination of laboratory facilities or exposure of personnel to
asbestos. Asbestos spills should be cleaned up with wet methods and/or a
High Efficiency Particulate-Air (HEPA) filtered vacuum.
Caution: Do not use a vacuum without a HEPA filter--It will disperse
fine asbestos fibers in the air.
6.2. Equipment
6.2.1. Phase contrast microscope with binocular or trinocular head.
6.2.2. Widefield or Huygenian 10X eyepieces (Note: The eyepiece
containing the graticule must be a focusing eyepiece. Use a 40X phase
objective with a numerical aperture of 0.65 to 0.75).
6.2.3. Kohler illumination (if possible) with green or blue filter.
6.2.4. Walton-Beckett Graticule, type G-22 with 100 2 [micro]m projected diameter.
6.2.5. Mechanical stage.
A rotating mechanical stage is convenient for use with polarized
light.
6.2.6. Phase telescope.
6.2.7. Stage micrometer with 0.01-mm subdivisions.
6.2.8. Phase-shift test slide, mark II (Available from PTR optics
Ltd., and also McCrone).
6.2.9. Precleaned glass slides, 25 mm x 75 mm. One end can be
frosted for convenience in writing sample numbers, etc., or paste-on
labels can be used.
6.2.10. Cover glass 1 \1/2\.
6.2.11. Scalpel (10, curved blade).
6.2.12. Fine tipped forceps.
6.2.13. Aluminum block for clearing filter (see Appendix D and
Figure 4).
6.2.14. Automatic adjustable pipette, 100- to 500-[micro]L.
6.2.15. Micropipette, 5 [micro]L.
6.3. Reagents
6.3.1. Acetone (HPLC grade).
6.3.2. Triacetin (glycerol triacetate).
6.3.3. Lacquer or nail polish.
6.4. Standard Preparation
A way to prepare standard asbestos samples of known concentration
has not been developed. It is possible to prepare replicate samples of
nearly equal concentration. This has been performed through the PAT
program. These asbestos samples are distributed by the AIHA to
participating laboratories.
Since only about one-fourth of a 25-mm sample membrane is required
for an asbestos count, any PAT sample can serve as a ``standard'' for
replicate counting.
6.5. Sample Mounting
Note: See Safety Precautions in Section 6.1. before proceeding. The
objective is to produce samples with a smooth (non-grainy) background in
a medium with a refractive index of approximately 1.46. The technique
below collapses the filter for easier focusing and produces permanent
mounts which are useful for quality control and interlaboratory
comparison.
[[Page 37]]
An aluminum block or similar device is required for sample
preparation.
6.5.1. Heat the aluminum block to about 70 [deg]C. The hot block
should not be used on any surface that can be damaged by either the heat
or from exposure to acetone.
6.5.2. Ensure that the glass slides and cover glasses are free of
dust and fibers.
6.5.3. Remove the top plug to prevent a vacuum when the cassette is
opened. Clean the outside of the cassette if necessary. Cut the seal
and/or tape on the cassette with a razor blade. Very carefully separate
the base from the extension cowl, leaving the filter and backup pad in
the base.
6.5.4. With a rocking motion cut a triangular wedge from the filter
using the scalpel. This wedge should be one-sixth to one-fourth of the
filter. Grasp the filter wedge with the forceps on the perimeter of the
filter which was clamped between the cassette pieces. DO NOT TOUCH the
filter with your finger. Place the filter on the glass slide sample side
up. Static electricity will usually keep the filter on the slide until
it is cleared.
6.5.5. Place the tip of the micropipette containing about 200
[micro]L acetone into the aluminum block. Insert the glass slide into
the receiving slot in the aluminum block. Inject the acetone into the
block with slow, steady pressure on the plunger while holding the
pipette firmly in place. Wait 3 to 5 seconds for the filter to clear,
then remove the pipette and slide from the aluminum block.
6.5.6. Immediately (less than 30 seconds) place 2.5 to 3.5 [micro]L
of triacetin on the filter (Note: Waiting longer than 30 seconds will
result in increased index of refraction and decreased contrast between
the fibers and the preparation. This may also lead to separation of the
cover slip from the slide).
6.5.7. Lower a cover slip gently onto the filter at a slight angle
to reduce the possibility of forming air bubbles. If more than 30
seconds have elapsed between acetone exposure and triacetin application,
glue the edges of the cover slip to the slide with lacquer or nail
polish.
6.5.8. If clearing is slow, warm the slide for 15 min on a hot plate
having a surface temperature of about 50 [deg]C to hasten clearing. The
top of the hot block can be used if the slide is not heated too long.
6.5.9. Counting may proceed immediately after clearing and mounting
are completed.
6.6. Sample Analysis
Completely align the microscope according to the manufacturer's
instructions. Then, align the microscope using the following general
alignment routine at the beginning of every counting session and more
often if necessary.
6.6.1. Alignment
(1) Clean all optical surfaces. Even a small amount of dirt can
significantly degrade the image.
(2) Rough focus the objective on a sample.
(3) Close down the field iris so that it is visible in the field of
view. Focus the image of the iris with the condenser focus. Center the
image of the iris in the field of view.
(4) Install the phase telescope and focus on the phase rings.
Critically center the rings. Misalignment of the rings results in
astigmatism which will degrade the image.
(5) Place the phase-shift test slide on the microscope stage and
focus on the lines. The analyst must see line set 3 and should see at
least parts of 4 and 5 but, not see line set 6 or 6. A microscope/
microscopist combination which does not pass this test may not be used.
6.6.2. Counting Fibers
(1) Place the prepared sample slide on the mechanical stage of the
microscope. Position the center of the wedge under the objective lens
and focus upon the sample.
(2) Start counting from one end of the wedge and progress along a
radial line to the other end (count in either direction from perimeter
to wedge tip). Select fields randomly, without looking into the
eyepieces, by slightly advancing the slide in one direction with the
mechanical stage control.
(3) Continually scan over a range of focal planes (generally the
upper 10 to 15 [micro]m of the filter surface) with the fine focus
control during each field count. Spend at least 5 to 15 seconds per
field.
(4) Most samples will contain asbestos fibers with fiber diameters
less than 1 [micro]m. Look carefully for faint fiber images. The small
diameter fibers will be very hard to see. However, they are an important
contribution to the total count.
(5) Count only fibers equal to or longer than 5 [micro]m. Measure
the length of curved fibers along the curve.
(6) Count fibers which have a length to width ratio of 3:1 or
greater.
(7) Count all the fibers in at least 20 fields. Continue counting
until either 100 fibers are counted or 100 fields have been viewed;
whichever occurs first. Count all the fibers in the final field.
(8) Fibers lying entirely within the boundary of the Walton-Beckett
graticule field shall receive a count of 1. Fibers crossing the boundary
once, having one end within the circle shall receive a count of \1/2\.
Do not count any fiber that crosses the graticule boundary more than
once. Reject and do not count any other fibers even though they may be
visible outside the graticule area. If a fiber touches the circle, it is
considered to cross the line.
(9) Count bundles of fibers as one fiber unless individual fibers
can be clearly identified and each individual fiber is clearly not
[[Page 38]]
connected to another counted fiber. See Figure 1 for counting
conventions.
(10) Record the number of fibers in each field in a consistent way
such that filter non-uniformity can be assessed.
(11) Regularly check phase ring alignment.
(12) When an agglomerate (mass of material) covers more than 25% of
the field of view, reject the field and select another. Do not include
it in the number of fields counted.
(13) Perform a ``blind recount'' of 1 in every 10 filter wedges
(slides). Re-label the slides using a person other than the original
counter.
6.7. Fiber Identification
As previously mentioned in Section 1.3., PCM does not provide
positive confirmation of asbestos fibers. Alternate differential
counting techniques should be used if discrimination is desirable.
Differential counting may include primary discrimination based on
morphology, polarized light analysis of fibers, or modification of PCM
data by Scanning Electron or Transmission Electron Microscopy.
A great deal of experience is required to routinely and correctly
perform differential counting. It is discouraged unless it is legally
necessary. Then, only if a fiber is obviously not asbestos should it be
excluded from the count. Further discussion of this technique can be
found in reference 8.10.
If there is a question whether a fiber is asbestos or not, follow
the rule:
``WHEN IN DOUBT, COUNT.''
6.8. Analytical Recommendations--Quality Control System
6.8.1. All individuals performing asbestos analysis must have taken
the NIOSH course for sampling and evaluating airborne asbestos or an
equivalent course.
6.8.2. Each laboratory engaged in asbestos counting shall set up a
slide trading arrangement with at least two other laboratories in order
to compare performance and eliminate inbreeding of error. The slide
exchange occurs at least semiannually. The round robin results shall be
posted where all analysts can view individual analyst's results.
6.8.3. Each laboratory engaged in asbestos counting shall
participate in the Proficiency Analytical Testing Program, the Asbestos
Analyst Registry or equivalent.
6.8.4. Each analyst shall select and count prepared slides from a
``slide bank''. These are quality assurance counts. The slide bank shall
be prepared using uniformly distributed samples taken from the workload.
Fiber densities should cover the entire range routinely analyzed by the
laboratory. These slides are counted blind by all counters to establish
an original standard deviation. This historical distribution is compared
with the quality assurance counts. A counter must have 95% of all
quality control samples counted within three standard deviations of the
historical mean. This count is then integrated into a new historical
mean and standard deviation for the slide.
The analyses done by the counters to establish the slide bank may be
used for an interim quality control program if the data are treated in a
proper statistical fashion.
7. Calculations
7.1. Calculate the estimated airborne asbestos fiber concentration
on the filter sample using the following formula:
where:
AC = Airborne fiber concentration
[GRAPHIC] [TIFF OMITTED] TR10AU94.000
FB = Total number of fibers greater than 5 [micro]m counted
FL = Total number of fields counted on the filter
BFB = Total number of fibers greater than 5 [micro]m counted in the
blank
BFL = Total number of fields counted on the blank
ECA = Effective collecting area of filter (385 mm\2\ nominal for a 25-mm
filter.)
FR = Pump flow rate (L/min)
MFA = Microscope count field area (mm\2\). This is 0.00785 mm\2\ for a
Walton-Beckett Graticule.
T = Sample collection time (min)
1,000 = Conversion of L to cc
Note: The collection area of a filter is seldom equal to 385 mm\2\.
It is appropriate for laboratories to routinely monitor the exact
diameter using an inside micrometer. The collection area is calculated
according to the formula:
Area = [pi](d/2)\2\
7.2. Short-cut Calculation
Since a given analyst always has the same interpupillary distance,
the number of fields per filter for a particular analyst will remain
constant for a given size filter. The field size for that analyst is
constant (i.e. the analyst is using an assigned microscope and is not
changing the reticle).
For example, if the exposed area of the filter is always 385 mm\2\
and the size of the field is always 0.00785 mm\2\, the number of fields
per filter will always be 49,000. In addition it is necessary to convert
liters of air to cc. These three constants can then be combined such
that ECA/(1,000 x MFA)=49. The previous equation simplifies to:
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[GRAPHIC] [TIFF OMITTED] TR10AU94.001
7.3. Recount Calculations
As mentioned in step 13 of Section 6.6.2., a ``blind recount'' of
10% of the slides is performed. In all cases, differences will be
observed between the first and second counts of the same filter wedge.
Most of these differences will be due to chance alone, that is, due to
the random variability (precision) of the count method. Statistical
recount criteria enables one to decide whether observed differences can
be explained due to chance alone or are probably due to systematic
differences between analysts, microscopes, or other biasing factors.
The following recount criterion is for a pair of counts that
estimate AC in fibers/cc. The criterion is given at the type-I error
level. That is, there is 5% maximum risk that we will reject a pair of
counts for the reason that one might be biased, when the large observed
difference is really due to chance.
Reject a pair of counts if:
[GRAPHIC] [TIFF OMITTED] TR29JN95.000
Where:
AC1 = lower estimated airborne fiber concentration
AC2 = higher estimated airborne fiber concentration
ACavg = average of the two concentration estimates
CVFB = CV for the average of the two concentration estimates
If a pair of counts are rejected by this criterion then, recount the
rest of the filters in the submitted set. Apply the test and reject any
other pairs failing the test. Rejection shall include a memo to the
industrial hygienist stating that the sample failed a statistical test
for homogeneity and the true air concentration may be significantly
different than the reported value.
7.4. Reporting Results
Report results to the industrial hygienist as fibers/cc. Use two
significant figures. If multiple analyses are performed on a sample, an
average of the results is to be reported unless any of the results can
be rejected for cause.
8. References
8.1. Dreesen, W.C., et al, U.S. Public Health Service: A Study of
Asbestosis in the Asbestos Textile Industry, (Public Health Bulletin No.
241), US Treasury Dept., Washington, DC, 1938.
8.2. Asbestos Research Council: The Measurement of Airborne Asbestos
Dust by the Membrane Filter Method (Technical Note), Asbestos Research
Council, Rockdale, Lancashire, Great Britain, 1969.
8.3. Bayer, S.G., Zumwalde, R.D., Brown, T.A., Equipment and
Procedure for Mounting Millipore Filters and Counting Asbestos Fibers by
Phase Contrast Microscopy, Bureau of Occupational Health, U.S. Dept. of
Health, Education and Welfare, Cincinnati, OH, 1969.
8.4. NIOSH Manual of Analytical Methods, 2nd ed., Vol. 1 (DHEW/NIOSH
Pub. No. 77-157-A). National Institute for Occupational Safety and
Health, Cincinnati, OH, 1977. pp. 239-1-239-21.
8.5. Asbestos, Code of Federal Regulations 29 CFR 1910.1001. 1971.
8.6. Occupational Exposure to Asbestos, Tremolite, Anthophyllite,
and Actinolite. Final Rule, Federal Register 51:119 (20 June 1986).
pp.22612-22790.
8.7. Asbestos, Tremolite, Anthophyllite, and Actinolite, Code of
Federal Regulations 1910.1001. 1988. pp 711-752.
8.8. Criteria for a Recommended Standard--Occupational Exposure to
Asbestos (DHEW/NIOSH Pub. No. HSM 72-10267), National Institute for
Occupational Safety and Health NIOSH, Cincinnati,OH, 1972. pp. III-1-
III-24.
8.9. Leidel, N.A., Bayer,S.G., Zumwalde, R.D.,Busch, K.A., USPHS/
NIOSH Membrane Filter Method for Evaluating Airborne Asbestos Fibers
(DHEW/NIOSH Pub. No. 79-127). National Institute for Occupational Safety
and Health, Cincinnati, OH, 1979.
8.10. Dixon, W.C., Applications of Optical Microscopy in Analysis of
Asbestos and Quartz, Analytical Techniques in Occupational Health
Chemistry, edited by D.D. Dollberg and A.W. Verstuyft. Wash. DC:
American Chemical Society, (ACS Symposium Series 120) 1980. pp. 13-41.
Quality Control
The OSHA asbestos regulations require each laboratory to establish a
quality control program. The following is presented as an example of how
the OSHA-SLTC constructed its internal CV curve as part of meeting this
requirement. Data is from 395 samples collected during OSHA compliance
inspections and analyzed from October 1980 through April 1986.
Each sample was counted by 2 to 5 different counters independently
of one another. The standard deviation and the CV statistic was
calculated for each sample. This data was then plotted on a graph of CV
[[Page 40]]
vs. fibers/mm\2\. A least squares regression was performed using the
following equation:
CV =
antilog110[A(log10(x))\2\+B(log10(x))+C]
where:
x = the number of fibers/mm\2\
Application of least squares gave:
A = 0.182205
B = -0.973343
C = 0.327499
Using these values, the equation becomes:
CV = antilog10 [0.182205(log10 (x))\2\-
0.973343(log10 (x))+0.327499]
Sampling Pump Flow Rate Corrections
This correction is used if a difference greater than 5% in ambient
temperature and/or pressure is noted between calibration and sampling
sites and the pump does not compensate for the differences.
[GRAPHIC] [TIFF OMITTED] TR10AU94.003
Where:
Qact = actual flow rate
Qcal = calibrated flow rate (if a rotameter was used, the
rotameter value)
Pcal = uncorrected air pressure at calibration
Pact = uncorrected air pressure at sampling site
Tact = temperature at sampling site (K)
Tcal = temperature at calibration (K)
Walton-Beckett Graticule
When ordering the Graticule for asbestos counting, specify the exact
disc diameter needed to fit the ocular of the microscope and the
diameter (mm) of the circular counting area. Instructions for measuring
the dimensions necessary are listed:
(1) Insert any available graticule into the focusing eyepiece and
focus so that the graticule lines are sharp and clear.
(2) Align the microscope.
(3) Place a stage micrometer on the microscope object stage and
focus the microscope on the graduated lines.
(4) Measure the magnified grid length, PL ([micro]m), using the
stage micrometer.
(5) Remove the graticule from the microscope and measure its actual
grid length, AL (mm). This can be accomplished by using a mechanical
stage fitted with verniers, or a jeweler's loupe with a direct reading
scale.
(6) Let D=100 [micro]m. Calculate the circle diameter, dc
(mm), for the Walton-Beckett graticule and specify the diameter when
making a purchase:
[GRAPHIC] [TIFF OMITTED] TR10AU94.004
Example: If PL=108 [micro]m, AL=2.93 mm and D=100 [micro]m, then,
[GRAPHIC] [TIFF OMITTED] TR10AU94.005
(7) Each eyepiece-objective-reticle combination on the microscope
must be calibrated. Should any of the three be changed (by zoom
adjustment, disassembly, replacement, etc.), the combination must be
recalibrated. Calibration may change if interpupillary distance is
changed. Measure the field diameter, D (acceptable range: 1002 [micro]m) with a stage micrometer upon receipt of the
graticule from the manufacturer. Determine the field area (mm\2\).
Field Area=[Delta](D/2)\2\
If D=100 [micro]m=0.1 mm, then
Field Area=[Delta](0.1 mm/2)\2\=0.00785 mm\2\
The Graticule is available from: Graticules Ltd., Morley Road,
Tonbridge TN9 IRN, Kent, England (Telephone 011-44-732-359061). Also
available from PTR Optics Ltd., 145 Newton Street, Waltham, MA 02154
[telephone (617) 891-6000] or McCrone Accessories and Components, 2506
S. Michigan Ave., Chicago, IL 60616 [phone (312)-842-7100]. The
graticule is custom made for each microscope.
Counts for the Fibers in the Figure
------------------------------------------------------------------------
Structure No. Count Explanation
------------------------------------------------------------------------
1 to 6...................... 1 Single fibers all contained
within the circle.
7........................... \1/2\ Fiber crosses circle once.
8........................... 0 Fiber too short.
9........................... 2 Two crossing fibers.
10........................... 0 Fiber outside graticule.
11........................... 0 Fiber crosses graticule twice.
12........................... \1/2\ Although split, fiber only
crosses once.
------------------------------------------------------------------------
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Appendix C to Sec. 1910.1001 [Reserved]
Appendix D to Sec. 1910.1001--Medical Questionnaires; Mandatory
This mandatory appendix contains the medical questionnaires that
must be administered to all employees who are exposed to asbestos above
the permissible exposure limit, and who will therefore be included in
their employer's medical surveillance program. Part 1 of the appendix
contains the Initial Medical Questionnaire, which must be obtained for
all new hires who will be covered by the medical surveillance
requirements. Part 2 includes the abbreviated Periodical Medical
Questionnaire, which must be administered to all employees who are
provided periodic medical examinations under the medical surveillance
provisions of the standard.
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Appendix E to Sec. 1910.1001--Interpretation and Classification of
Chest Roentgenograms--Mandatory
(a) Chest roentgenograms shall be interpreted and classified in
accordance with a professionally accepted Classification system and
recorded on an interpretation form following the format of the CDC/NIOSH
(M) 2.8 form. As a minimum, the content within the bold lines of this
form (items 1 though 4) shall be included. This form is not to be
submitted to NIOSH.
(b) Roentgenograms shall be interpreted and classified only by a B-
reader, a board eligible/certified radiologist, or an experienced
physician with known expertise in pneumoconioses.
(c) All interpreters, whenever interpreting chest roentgenograms
made under this section, shall have immediately available for reference
a complete set of the ILO-U/C International Classification of
Radiographs for Pneumoconioses, 1980.
Appendix F to Sec. 1910.1001--Work Practices and Engineering Controls
for Automotive Brake and Clutch Inspection, Disassembly, Repair and
Assembly--Mandatory
This mandatory appendix specifies engineering controls and work
practices that must be implemented by the employer during automotive
brake and clutch inspection, disassembly, repair, and assembly
operations. Proper use of these engineering controls and work practices
by trained employees will reduce employees' asbestos exposure below the
permissible exposure level during clutch and brake inspection,
disassembly, repair, and assembly operations. The employer shall
institute engineering controls and work practices using either the
method set forth in paragraph [A] or paragraph [B] of this appendix, or
any other method which the employer can demonstrate to be equivalent in
terms of reducing employee exposure to asbestos as defined and which
meets the requirements described in paragraph [C] of
[[Page 54]]
this appendix, for those facilities in which no more than 5 pairs of
brakes or 5 clutches are inspected, disassembled, reassembled and/or
repaired per week, the method set forth in paragraph [D] of this
appendix may be used:
[A] Negative Pressure Enclosure/HEPA Vacuum System Method
(1) The brake and clutch inspection, disassembly, repair, and
assembly operations shall be enclosed to cover and contain the clutch or
brake assembly and to prevent the release of asbestos fibers into the
worker's breathing zone.
(2) The enclosure shall be sealed tightly and thoroughly inspected
for leaks before work begins on brake and clutch inspection,
disassembly, repair, and assembly.
(3) The enclosure shall be such that the worker can clearly see the
operation and shall provide impermeable sleeves through which the worker
can handle the brake and clutch inspection, disassembly, repair and
assembly. The integrity of the sleeves and ports shall be examined
before work begins.
(4) A HEPA-filtered vacuum shall be employed to maintain the
enclosure under negative pressure throughout the operation. Compressed-
air may be used to remove asbestos fibers or particles from the
enclosure.
(5) The HEPA vacuum shall be used first to loosen the asbestos
containing residue from the brake and clutch parts and then to evacuate
the loosened asbestos containing material from the enclosure and capture
the material in the vacuum filter.
(6) The vacuum's filter, when full, shall be first wetted with a
fine mist of water, then removed and placed immediately in an
impermeable container, labeled according to paragraph (j)(4) of this
section and disposed of according to paragraph (k) of this section.
(7) Any spills or releases of asbestos containing waste material
from inside of the enclosure or vacuum hose or vacuum filter shall be
immediately cleaned up and disposed of according to paragraph (k) of
this section.
[B] Low Pressure/Wet Cleaning Method
(1) A catch basin shall be placed under the brake assembly,
positioned to avoid splashes and spills.
(2) The reservoir shall contain water containing an organic solvent
or wetting agent. The flow of liquid shall be controlled such that the
brake assembly is gently flooded to prevent the asbestos-containing
brake dust from becoming airborne.
(3) The aqueous solution shall be allowed to flow between the brake
drum and brake support before the drum is removed.
(4) After removing the brake drum, the wheel hub and back of the
brake assembly shall be thoroughly wetted to suppress dust.
(5) The brake support plate, brake shoes and brake components used
to attach the brake shoes shall be thoroughly washed before removing the
old shoes.
(6) In systems using filters, the filters, when full, shall be first
wetted with a fine mist of water, then removed and placed immediately in
an impermeable container, labeled according to paragraph (j)(4) of this
section and disposed of according to paragraph (k) of this section.
(7) Any spills of asbestos-containing aqueous solution or any
asbestos-containing waste material shall be cleaned up immediately and
disposed of according to paragraph (k) of this section.
(8) The use of dry brushing during low pressure/wet cleaning
operations is prohibited.
[C] Equivalent Methods
An equivalent method is one which has sufficient written detail so
that it can be reproduced and has been demonstrated that the exposures
resulting from the equivalent method are equal to or less than the
exposures which would result from the use of the method described in
paragraph [A] of this appendix. For purposes of making this comparison,
the employer shall assume that exposures resulting from the use of the
method described in paragraph [A] of this appendix shall not exceed
0.016 f/cc, as measured by the OSHA reference method and as averaged
over at least 18 personal samples.
[D] Wet Method.
(1) A spray bottle, hose nozzle, or other implement capable of
delivering a fine mist of water or amended water or other delivery
system capable of delivering water at low pressure, shall be used to
first thoroughly wet the brake and clutch parts. Brake and clutch
components shall then be wiped clean with a cloth.
(2) The cloth shall be placed in an impermeable container, labelled
according to paragraph (j)(4) of this section and then disposed of
according to paragraph (k) of this section, or the cloth shall be
laundered in a way to prevent the release of asbestos fibers in excess
of 0.1 fiber per cubic centimeter of air.
(3) Any spills of solvent or any asbestos containing waste material
shall be cleaned up immediately according to paragraph (k) of this
section.
(4) The use of dry brushing during the wet method operations is
prohibited.
Appendix G to Sec. 1910.1001--Substance Technical Information for
Asbestos--Non-Mandatory
I. Substance Identification
A. Substance: ``Asbestos'' is the name of a class of magnesium-
silicate minerals that
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occur in fibrous form. Minerals that are included in this group are
chrysotile, crocidolite, amosite, tremolite asbestos, anthophyllite
asbestos, and actinolite asbestos.
B. Asbestos is used in the manufacture of heat-resistant clothing,
automative brake and clutch linings, and a variety of building materials
including floor tiles, roofing felts, ceiling tiles, asbestos-cement
pipe and sheet, and fire-resistant drywall. Asbestos is also present in
pipe and boiler insulation materials, and in sprayed-on materials
located on beams, in crawlspaces, and between walls.
C. The potential for a product containing asbestos to release
breatheable fibers depends on its degree of friability. Friable means
that the material can be crumbled with hand pressure and is therefore
likely to emit fibers. The fibrous or fluffy sprayed-on materials used
for fireproofing, insulation, or sound proofing are considered to be
friable, and they readily release airborne fibers if disturbed.
Materials such as vinyl-asbestos floor tile or roofing felts are
considered nonfriable and generally do not emit airborne fibers unless
subjected to sanding or sawing operations. Asbestos-cement pipe or sheet
can emit airborne fibers if the materials are cut or sawed, or if they
are broken during demolition operations.
D. Permissible exposure: Exposure to airborne asbestos fibers may
not exceed 0.2 fibers per cubic centimeter of air (0.1 f/cc) averaged
over the 8-hour workday.
II. Health Hazard Data
A. Asbestos can cause disabling respiratory disease and various
types of cancers if the fibers are inhaled. Inhaling or ingesting fibers
from contaminated clothing or skin can also result in these diseases.
The symptoms of these diseases generally do not appear for 20 or more
years after initial exposure.
B. Exposure to asbestos has been shown to cause lung cancer,
mesothelioma, and cancer of the stomach and colon. Mesothelioma is a
rare cancer of the thin membrane lining of the chest and abdomen.
Symptoms of mesothelioma include shortness of breath, pain in the walls
of the chest, and/or abdominal pain.
III. Respirators and Protective Clothing
A. Respirators: You are required to wear a respirator when
performing tasks that result in asbestos exposure that exceeds the
permissible exposure limit (PEL) of 0.1 f/cc. These conditions can occur
while your employer is in the process of installing engineering controls
to reduce asbestos exposure, or where engineering controls are not
feasible to reduce asbestos exposure. Air-purifying respirators equipped
with a high-efficiency particulate air (HEPA) filter can be used where
airborne asbestos fiber concentrations do not exceed 2 f/cc; otherwise,
air-supplied, positive-pressure, full facepiece respirators must be
used. Disposable respirators or dust masks are not permitted to be used
for asbestos work. For effective protection, respirators must fit your
face and head snugly. Your employer is required to conduct fit tests
when you are first assigned a respirator and every 6 months thereafter.
Respirators should not be loosened or removed in work situations where
their use is required.
B. Protective clothing: You are required to wear protective clothing
in work areas where asbestos fiber concentrations exceed the permissible
exposure limit.
IV. Disposal Procedures and Cleanup
A. Wastes that are generated by processes where asbestos is present
include:
1. Empty asbestos shipping containers.
2. Process wastes such as cuttings, trimmings, or reject material.
3. Housekeeping waste from sweeping or vacuuming.
4. Asbestos fireproofing or insulating material that is removed from
buildings.
5. Building products that contain asbestos removed during building
renovation or demolition.
6. Contaminated disposable protective clothing.
B. Empty shipping bags can be flattened under exhaust hoods and
packed into airtight containers for disposal. Empty shipping drums are
difficult to clean and should be sealed.
C. Vacuum bags or disposable paper filters should not be cleaned,
but should be sprayed with a fine water mist and placed into a labeled
waste container.
D. Process waste and housekeeping waste should be wetted with water
or a mixture of water and surfactant prior to packaging in disposable
containers.
E. Material containing asbestos that is removed from buildings must
be disposed of in leak-tight 6-mil thick plastic bags, plastic-lined
cardboard containers, or plastic-lined metal containers. These wastes,
which are removed while wet, should be sealed in containers before they
dry out to minimize the release of asbestos fibers during handling.
V. Access to Information
A. Each year, your employer is required to inform you of the
information contained in this standard and appendices for asbestos. In
addition, your employer must instruct you in the proper work practices
for handling materials containing asbestos, and the correct use of
protective equipment.
B. Your employer is required to determine whether you are being
exposed to asbestos. You or your representative has the right to observe
employee measurements and to
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record the results obtained. Your employer is required to inform you of
your exposure, and, if you are exposed above the permissible limit, he
or she is required to inform you of the actions that are being taken to
reduce your exposure to within the permissible limit.
C. Your employer is required to keep records of your exposures and
medical examinations. These exposure records must be kept for at least
thirty (30) years. Medical records must be kept for the period of your
employment plus thirty (30) years.
D. Your employer is required to release your exposure and medical
records to your physician or designated representative upon your written
request.
Appendix H to Sec. 1910.1001--Medical Surveillance Guidelines for
Asbestos Non-Mandatory
I. Route of Entry Inhalation, Ingestion
II. Toxicology
Clinical evidence of the adverse effects associated with exposure to
asbestos is present in the form of several well-conducted
epidemiological studies of occupationally exposed workers, family
contacts of workers, and persons living near asbestos mines. These
studies have shown a definite association between exposure to asbestos
and an increased incidence of lung cancer, pleural and peritoneal
mesothelioma, gastrointestinal cancer, and asbestosis. The latter is a
disabling fibrotic lung disease that is caused only by exposure to
asbestos. Exposure to asbestos has also been associated with an
increased incidence of esophageal, kidney, laryngeal, pharyngeal, and
buccal cavity cancers. As with other known chronic occupational
diseases, disease associated with asbestos generally appears about 20
years following the first occurrence of exposure: There are no known
acute effects associated with exposure to asbestos.
Epidemiological studies indicate that the risk of lung cancer among
exposed workers who smoke cigarettes is greatly increased over the risk
of lung cancer among non-exposed smokers or exposed nonsmokers. These
studies suggest that cessation of smoking will reduce the risk of lung
cancer for a person exposed to asbestos but will not reduce it to the
same level of risk as that existing for an exposed worker who has never
smoked.
III. Signs and Symptoms of Exposure-Related Disease
The signs and symptoms of lung cancer or gastrointestinal cancer
induced by exposure to asbestos are not unique, except that a chest X-
ray of an exposed patient with lung cancer may show pleural plaques,
pleural calcification, or pleural fibrosis. Symptoms characteristic of
mesothelioma include shortness of breath, pain in the walls of the
chest, or abdominal pain. Mesothelioma has a much longer latency period
compared with lung cancer (40 years versus 15-20 years), and
mesothelioma is therefore more likely to be found among workers who were
first exposed to asbestos at an early age. Mesothelioma is always fatal.
Asbestosis is pulmonary fibrosis caused by the accumulation of
asbestos fibers in the lungs. Symptoms include shortness of breath,
coughing, fatigue, and vague feelings of sickness. When the fibrosis
worsens, shortness of breath occurs even at rest. The diagnosis of
asbestosis is based on a history of exposure to asbestos, the presence
of characteristic radiologic changes, end-inspiratory crackles (rales),
and other clinical features of fibrosing lung disease. Pleural plaques
and thickening are observed on X-rays taken during the early stages of
the disease. Asbestosis is often a progressive disease even in the
absence of continued exposure, although this appears to be a highly
individualized characteristic. In severe cases, death may be caused by
respiratory or cardiac failure.
IV. Surveillance and Preventive Considerations
As noted above, exposure to asbestos has been linked to an increased
risk of lung cancer, mesothelioma, gastrointestinal cancer, and
asbestosis among occupationally exposed workers. Adequate screening
tests to determine an employee's potential for developing serious
chronic diseases, such as cancer, from exposure to asbestos do not
presently exist. However, some tests, particularly chest X-rays and
pulmonary function tests, may indicate that an employee has been
overexposed to asbestos increasing his or her risk of developing
exposure-related chronic diseases. It is important for the physician to
become familiar with the operating conditions in which occupational
exposure to asbestos is likely to occur. This is particularly important
in evaluating medical and work histories and in conducting physical
examinations. When an active employee has been identified as having been
overexposed to asbestos, measures taken by the employer to eliminate or
mitigate further exposure should also lower the risk of serious long-
term consequences.
The employer is required to institute a medical surveillance program
for all employees who are or will be exposed to asbestos at or above the
permissible exposure limit (0.1 fiber per cubic centimeter of air). All
examinations and procedures must be performed by or under the
supervision of a licensed physician, at a reasonable time and place, and
at no cost to the employee.
Although broad latitude is given to the physician in prescribing
specific tests to be
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included in the medical surveillance program, OSHA requires inclusion of
the following elements in the routine examination:
(i) Medical and work histories with special emphasis directed to
symptoms of the respiratory system, cardiovascular system, and digestive
tract.
(ii) Completion of the respiratory disease questionnaire contained
in Appendix D.
(iii) A physical examination including a chest roentgenogram and
pulmonary function test that includes measurement of the employee's
forced vital capacity (FVC) and forced expiratory volume at one second
(FEV1).
(iv) Any laboratory or other test that the examining physician deems
by sound medical practice to be necessary.
The employer is required to make the prescribed tests available at
least annually to those employees covered; more often than specified if
recommended by the examining physician; and upon termination of
employment.
The employer is required to provide the physician with the following
information: A copy of this standard and appendices; a description of
the mployee's duties as they relate to asbestos exposure; the employee's
representative level of exposure to asbestos; a description of any
personal protective and respiratory equipment used; and information from
previous medical examinations of the affected employee that is not
otherwise available to the physician. Making this information available
to the physician will aid in the evaluation of the employee's health in
relation to assigned duties and fitness to wear personal protective
equipment, if required.
The employer is required to obtain a written opinion from the
examining physician containing the results of the medical examination;
the physician's opinion as to whether the employee has any detected
medical conditions that would place the employee at an increased risk of
exposure-related disease; any recommended limitations on the employee or
on the use of personal protective equipment; and a statement that the
employee has been informed by the physician of the results of the
medical examination and of any medical conditions related to asbestos
exposure that require further explanation or treatment. This written
opinion must not reveal specific findings or diagnoses unrelated to
exposure to asbestos, and a copy of the opinion must be provided to the
affected employee.
Appendix I to Sec. 1910.1001--Smoking Cessation Program Information For
Asbestos--Non-Mandatory
The following organizations provide smoking cessation information
and program material.
1. The National Cancer Institute operates a toll-free Cancer
Information Service (CIS) with trained personnel to help you. Call 1-
800-4-CANCER* to reach the CIS office serving your area, or write:
Office of Cancer Communications, National Cancer Institute, National
Institutes of Health, Building 31, Room 10A24, Bethesda, Maryland 20892.
2. American Cancer Society, 3340 Peachtree Road, NE., Atlanta,
Georgia 30062, (404) 320-3333.
The American Cancer Society (ACS) is a voluntary organization
composed of 58 divisions and 3,100 local units. Through ``The Great
American Smokeout'' in November, the annual Cancer Crusade in April, and
numerous educational materials, ACS helps people learn about the health
hazards of smoking and become successful ex-smokers.
3. American Heart Association, 7320 Greenville Avenue, Dallas, Texas
75231, (214) 750-5300.
The American Heart Association (AHA) is a voluntary organization
with 130,000 members (physicians, scientists, and laypersons) in 55
state and regional groups. AHA produces a variety of publications and
audiovisual materials about the effects of smoking on the heart. AHA
also has developed a guidebook for incorporating a weight-control
component into smoking cessation programs.
4. American Lung Association, 1740 Broadway, New York, New York
10019, (212) 245-8000.
A voluntary organization of 7,500 members (physicians, nurses, and
laypersons), the American Lung Association (ALA) conducts numerous
public information programs about the health effect of smoking. ALA has
59 state and 85 local units. The organization actively supports
legislation and information campaigns for non-smokers' rights and
provides help for smokers who want to quit, for example, through
``Freedom From Smoking,'' a self-help smoking cessation program.
5. Office on Smoking and Health, U.S. Department of Health and,
Human Services, 5600 Fishers Lane, Park Building, Room 110, Rockville,
Maryland 20857.
The Office on Smoking and Health (OSH) is the Department of Health
and Human Services' lead agency in smoking control. OSH has sponsored
distribution of publications on smoking-realted topics, such as free
flyers on relapse after initial quitting, helping a friend or family
member quit smoking, the health hazards of smoking, and the effects of
parental smoking on teenagers.
*In Hawaii, on Oahu call 524-1234 (call collect from neighboring
islands),
Spanish-speaking staff members are available during daytime hours to
callers from the following areas: California, Florida, Georgia,
Illinois, New Jersey (area code 210), New York, and Texas. Consult your
local
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telephone directory for listings of local chapters.
Appendix J to Sec. 1910.1001--Polarized Light Microscopy of Asbestos--
Non-Mandatory
Method number: ID-191
Matrix: Bulk
Collection Procedure
Collect approximately 1 to 2 grams of each type of material and
place into separate 20 mL scintillation vials.
Analytical Procedure
A portion of each separate phase is analyzed by gross examination,
phase-polar examination, and central stop dispersion microscopy.
Commercial manufacturers and products mentioned in this method are
for descriptive use only and do not constitute endorsements by USDOL-
OSHA. Similar products from other sources may be substituted.
1. Introduction
This method describes the collection and analysis of asbestos bulk
materials by light microscopy techniques including phase- polar
illumination and central-stop dispersion microscopy. Some terms unique
to asbestos analysis are defined below:
Amphibole: A family of minerals whose crystals are formed by long,
thin units which have two thin ribbons of double chain silicate with a
brucite ribbon in between. The shape of each unit is similar to an ``I
beam''. Minerals important in asbestos analysis include cummingtonite-
grunerite, crocidolite, tremolite-actinolite and anthophyllite.
Asbestos: A term for naturally occurring fibrous minerals. Asbestos
includes chrysotile, cummingtonite-grunerite asbestos (amosite),
anthophyllite asbestos, tremolite asbestos, crocidolite, actinolite
asbestos and any of these minerals which have been chemically treated or
altered. The precise chemical formulation of each species varies with
the location from which it was mined. Nominal compositions are listed:
Chrysotile...............................Mg3 Si2
O5(OH)4
Crocidolite (Riebeckite asbestos)........Na2
Fe3\2+\ Fe2\3+\ Si8
O22(OH)2
Cummingtonite-Grunerite asbestos (Amosite)..........(Mg,Fe)7
Si8 O22(OH)2
Tremolite-Actinolite asbestos................Ca2
(Mg,Fe)5 Si8
O22(OH)2
Anthophyllite asbestos.............(Mg,Fe)7 Si8
O22(OH)2
Asbestos Fiber: A fiber of asbestos meeting the criteria for a
fiber. (See section 3.5.)
Aspect Ratio: The ratio of the length of a fiber to its diameter
usually defined as ``length : width'', e.g. 3:1.
Brucite: A sheet mineral with the composition Mg(OH)2.
Central Stop Dispersion Staining (microscope): This is a dark field
microscope technique that images particles using only light refracted by
the particle, excluding light that travels through the particle
unrefracted. This is usually accomplished with a McCrone objective or
other arrangement which places a circular stop with apparent aperture
equal to the objective aperture in the back focal plane of the
microscope.
Cleavage Fragments: Mineral particles formed by the comminution of
minerals, especially those characterized by relatively parallel sides
and moderate aspect ratio.
Differential Counting: The term applied to the practice of excluding
certain kinds of fibers from a phase contrast asbestos count because
they are not asbestos.
Fiber: A particle longer than or equal to 5 [micro]m with a length
to width ratio greater than or equal to 3:1. This may include cleavage
fragments. (see section 3.5 of this appendix).
Phase Contrast: Contrast obtained in the microscope by causing light
scattered by small particles to destructively interfere with unscattered
light, thereby enhancing the visibility of very small particles and
particles with very low intrinsic contrast.
Phase Contrast Microscope: A microscope configured with a phase mask
pair to create phase contrast. The technique which uses this is called
Phase Contrast Microscopy (PCM).
Phase-Polar Analysis: This is the use of polarized light in a phase
contrast microscope. It is used to see the same size fibers that are
visible in air filter analysis. Although fibers finer than 1 [micro]m
are visible, analysis of these is inferred from analysis of larger
bundles that are usually present.
Phase-Polar Microscope: The phase-polar microscope is a phase
contrast microscope which has an analyzer, a polarizer, a first order
red plate and a rotating phase condenser all in place so that the
polarized light image is enhanced by phase contrast.
Sealing Encapsulant: This is a product which can be applied,
preferably by spraying, onto an asbestos surface which will seal the
surface so that fibers cannot be released.
Serpentine: A mineral family consisting of minerals with the general
composition Mg3(Si2O5(OH)4 having the
magnesium in brucite layer over a silicate layer. Minerals important in
asbestos analysis included in this family are chrysotile, lizardite,
antigorite.
1.1. History
Light microscopy has been used for well over 100 years for the
determination of mineral species. This analysis is carried out using
specialized polarizing microscopes as well as bright field microscopes.
The identification of minerals is an on-going process with many new
minerals described each year. The first recorded use of asbestos was
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in Finland about 2500 B.C. where the material was used in the mud wattle
for the wooden huts the people lived in as well as strengthening for
pottery. Adverse health aspects of the mineral were noted nearly 2000
years ago when Pliny the Younger wrote about the poor health of slaves
in the asbestos mines. Although known to be injurious for centuries, the
first modern references to its toxicity were by the British Labor
Inspectorate when it banned asbestos dust from the workplace in 1898.
Asbestosis cases were described in the literature after the turn of the
century. Cancer was first suspected in the mid 1930's and a causal link
to mesothelioma was made in 1965. Because of the public concern for
worker and public safety with the use of this material, several
different types of analysis were applied to the determination of
asbestos content. Light microscopy requires a great deal of experience
and craft. Attempts were made to apply less subjective methods to the
analysis. X-ray diffraction was partially successful in determining the
mineral types but was unable to separate out the fibrous portions from
the non-fibrous portions. Also, the minimum detection limit for asbestos
analysis by X-ray diffraction (XRD) is about 1%. Differential Thermal
Analysis (DTA) was no more successful. These provide useful
corroborating information when the presence of asbestos has been shown
by microscopy; however, neither can determine the difference between
fibrous and non-fibrous minerals when both habits are present. The same
is true of Infrared Absorption (IR).
When electron microscopy was applied to asbestos analysis, hundreds
of fibers were discovered present too small to be visible in any light
microscope. There are two different types of electron microscope used
for asbestos analysis: Scanning Electron Microscope (SEM) and
Transmission Electron Microscope (TEM). Scanning Electron Microscopy is
useful in identifying minerals. The SEM can provide two of the three
pieces of information required to identify fibers by electron
microscopy: morphology and chemistry. The third is structure as
determined by Selected Area Electron Diffraction--SAED which is
performed in the TEM. Although the resolution of the SEM is sufficient
for very fine fibers to be seen, accuracy of chemical analysis that can
be performed on the fibers varies with fiber diameter in fibers of less
than 0.2 [micro]m diameter. The TEM is a powerful tool to identify
fibers too small to be resolved by light microscopy and should be used
in conjunction with this method when necessary. The TEM can provide all
three pieces of information required for fiber identification. Most
fibers thicker than 1 [micro]m can adequately be defined in the light
microscope. The light microscope remains as the best instrument for the
determination of mineral type. This is because the minerals under
investigation were first described analytically with the light
microscope. It is inexpensive and gives positive identification for most
samples analyzed. Further, when optical techniques are inadequate, there
is ample indication that alternative techniques should be used for
complete identification of the sample.
1.2. Principle
Minerals consist of atoms that may be arranged in random order or in
a regular arrangement. Amorphous materials have atoms in random order
while crystalline materials have long range order. Many materials are
transparent to light, at least for small particles or for thin sections.
The properties of these materials can be investigated by the effect that
the material has on light passing through it. The six asbestos minerals
are all crystalline with particular properties that have been identified
and cataloged. These six minerals are anisotropic. They have a regular
array of atoms, but the arrangement is not the same in all directions.
Each major direction of the crystal presents a different regularity.
Light photons travelling in each of these main directions will encounter
different electrical neighborhoods, affecting the path and time of
travel. The techniques outlined in this method use the fact that light
traveling through fibers or crystals in different directions will behave
differently, but predictably. The behavior of the light as it travels
through a crystal can be measured and compared with known or determined
values to identify the mineral species. Usually, Polarized Light
Microscopy (PLM) is performed with strain-free objectives on a bright-
field microscope platform. This would limit the resolution of the
microscope to about 0.4 [micro]m. Because OSHA requires the counting and
identification of fibers visible in phase contrast, the phase contrast
platform is used to visualize the fibers with the polarizing elements
added into the light path. Polarized light methods cannot identify
fibers finer than about 1 [micro]m in diameter even though they are
visible. The finest fibers are usually identified by inference from the
presence of larger, identifiable fiber bundles. When fibers are present,
but not identifiable by light microscopy, use either SEM or TEM to
determine the fiber identity.
1.3. Advantages and Disadvantages
The advantages of light microcopy are:
(a) Basic identification of the materials was first performed by
light microscopy and gross analysis. This provides a large base of
published information against which to check analysis and analytical
technique.
(b) The analysis is specific to fibers. The minerals present can
exist in asbestiform, fibrous, prismatic, or massive varieties all at
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the same time. Therefore, bulk methods of analysis such as X-ray
diffraction, IR analysis, DTA, etc. are inappropriate where the material
is not known to be fibrous.
(c) The analysis is quick, requires little preparation time, and can
be performed on-site if a suitably equipped microscope is available.
The disadvantages are:
(a) Even using phase-polar illumination, not all the fibers present
may be seen. This is a problem for very low asbestos concentrations
where agglomerations or large bundles of fibers may not be present to
allow identification by inference.
(b) The method requires a great degree of sophistication on the part
of the microscopist. An analyst is only as useful as his mental catalog
of images. Therefore, a microscopist's accuracy is enhanced by
experience. The mineralogical training of the analyst is very important.
It is the basis on which subjective decisions are made.
(c) The method uses only a tiny amount of material for analysis.
This may lead to sampling bias and false results (high or low). This is
especially true if the sample is severely inhomogeneous.
(d) Fibers may be bound in a matrix and not distinguishable as
fibers so identification cannot be made.
1.4. Method Performance
1.4.1. This method can be used for determination of asbestos content
from 0 to 100% asbestos. The detection limit has not been adequately
determined, although for selected samples, the limit is very low,
depending on the number of particles examined. For mostly homogeneous,
finely divided samples, with no difficult fibrous interferences, the
detection limit is below 1%. For inhomogeneous samples (most samples),
the detection limit remains undefined. NIST has conducted proficiency
testing of laboratories on a national scale. Although each round is
reported statistically with an average, control limits, etc., the
results indicate a difficulty in establishing precision especially in
the low concentration range. It is suspected that there is significant
bias in the low range especially near 1%. EPA tried to remedy this by
requiring a mandatory point counting scheme for samples less than 10%.
The point counting procedure is tedious, and may introduce significant
biases of its own. It has not been incorporated into this method.
1.4.2. The precision and accuracy of the quantitation tests
performed in this method are unknown. Concentrations are easier to
determine in commercial products where asbestos was deliberately added
because the amount is usually more than a few percent. An analyst's
results can be ``calibrated'' against the known amounts added by the
manufacturer. For geological samples, the degree of homogeneity affects
the precision.
1.4.3. The performance of the method is analyst dependent. The
analyst must choose carefully and not necessarily randomly the portions
for analysis to assure that detection of asbestos occurs when it is
present. For this reason, the analyst must have adequate training in
sample preparation, and experience in the location and identification of
asbestos in samples. This is usually accomplished through substantial
on-the-job training as well as formal education in mineralogy and
microscopy.
1.5. Interferences
Any material which is long, thin, and small enough to be viewed
under the microscope can be considered an interference for asbestos.
There are literally hundreds of interferences in workplaces. The
techniques described in this method are normally sufficient to eliminate
the interferences. An analyst's success in eliminating the interferences
depends on proper training.
Asbestos minerals belong to two mineral families: the serpentines
and the amphiboles. In the serpentine family, the only common fibrous
mineral is chrysotile. Occasionally, the mineral antigorite occurs in a
fibril habit with morphology similar to the amphiboles. The amphibole
minerals consist of a score of different minerals of which only five are
regulated by federal standard: amosite, crocidolite, anthophyllite
asbestos, tremolite asbestos and actinolite asbestos. These are the only
amphibole minerals that have been commercially exploited for their
fibrous properties; however, the rest can and do occur occasionally in
asbestiform habit.
In addition to the related mineral interferences, other minerals
common in building material may present a problem for some
microscopists: gypsum, anhydrite, brucite, quartz fibers, talc fibers or
ribbons, wollastonite, perlite, attapulgite, etc. Other fibrous
materials commonly present in workplaces are: fiberglass, mineral wool,
ceramic wool, refractory ceramic fibers, kevlar, nomex, synthetic
fibers, graphite or carbon fibers, cellulose (paper or wood) fibers,
metal fibers, etc.
Matrix embedding material can sometimes be a negative interference.
The analyst may not be able to easily extract the fibers from the matrix
in order to use the method. Where possible, remove the matrix before the
analysis, taking careful note of the loss of weight. Some common matrix
materials are: vinyl, rubber, tar, paint, plant fiber, cement, and
epoxy. A further negative interference is that the asbestos fibers
themselves may be either too small to be seen in Phase contrast
Microscopy (PCM) or of a very low fibrous quality, having the appearance
of plant fibers. The analyst's ability to deal with these materials
increases with experience.
[[Page 61]]
1.6. Uses and Occupational Exposure
Asbestos is ubiquitous in the environment. More than 40% of the land
area of the United States is composed of minerals which may contain
asbestos. Fortunately, the actual formation of great amounts of asbestos
is relatively rare. Nonetheless, there are locations in which
environmental exposure can be severe such as in the Serpentine Hills of
California.
There are thousands of uses for asbestos in industry and the home.
Asbestos abatement workers are the most current segment of the
population to have occupational exposure to great amounts of asbestos.
If the material is undisturbed, there is no exposure. Exposure occurs
when the asbestos-containing material is abraded or otherwise disturbed
during maintenance operations or some other activity. Approximately 95%
of the asbestos in place in the United States is chrysotile.
Amosite and crocidolite make up nearly all the difference. Tremolite
and anthophyllite make up a very small percentage. Tremolite is found in
extremely small amounts in certain chrysotile deposits. Actinolite
exposure is probably greatest from environmental sources, but has been
identified in vermiculite containing, sprayed-on insulating materials
which may have been certified as asbestos-free.
1.7. Physical and Chemical Properties
The nominal chemical compositions for the asbestos minerals were
given in Section 1. Compared to cleavage fragments of the same minerals,
asbestiform fibers possess a high tensile strength along the fiber axis.
They are chemically inert, non- combustible, and heat resistant. Except
for chrysotile, they are insoluble in Hydrochloric acid (HCl).
Chrysotile is slightly soluble in HCl. Asbestos has high electrical
resistance and good sound absorbing characteristics. It can be woven
into cables, fabrics or other textiles, or matted into papers, felts,
and mats.
1.8. Toxicology (This Section is for Information Only and Should Not Be
Taken as OSHA Policy)
Possible physiologic results of respiratory exposure to asbestos are
mesothelioma of the pleura or peritoneum, interstitial fibrosis,
asbestosis, pneumoconiosis, or respiratory cancer. The possible
consequences of asbestos exposure are detailed in the NIOSH Criteria
Document or in the OSHA Asbestos Standards 29 CFR 1910.1001 and 29 CFR
1926.1101 and 29 CFR 1915.1001.
2. Sampling Procedure
2.1. Equipment for Sampling
(a) Tube or cork borer sampling device
(b) Knife
(c) 20 mL scintillation vial or similar vial
(d) Sealing encapsulant
2.2. Safety Precautions
Asbestos is a known carcinogen. Take care when sampling. While in an
asbestos-containing atmosphere, a properly selected and fit-tested
respirator should be worn. Take samples in a manner to cause the least
amount of dust. Follow these general guidelines:
(a) Do not make unnecessary dust.
(b) Take only a small amount (1 to 2 g).
(c) Tightly close the sample container.
(d) Use encapsulant to seal the spot where the sample was taken, if
necessary.
2.3. Sampling Procedure
Samples of any suspect material should be taken from an
inconspicuous place. Where the material is to remain, seal the sampling
wound with an encapsulant to eliminate the potential for exposure from
the sample site. Microscopy requires only a few milligrams of material.
The amount that will fill a 20 mL scintillation vial is more than
adequate. Be sure to collect samples from all layers and phases of
material. If possible, make separate samples of each different phase of
the material. This will aid in determining the actual hazard. DO NOT USE
ENVELOPES, PLASTIC OR PAPER BAGS OF ANY KIND TO COLLECT SAMPLES. The use
of plastic bags presents a contamination hazard to laboratory personnel
and to other samples. When these containers are opened, a bellows effect
blows fibers out of the container onto everything, including the person
opening the container.
If a cork-borer type sampler is available, push the tube through the
material all the way, so that all layers of material are sampled. Some
samplers are intended to be disposable. These should be capped and sent
to the laboratory. If a non-disposable cork borer is used, empty the
contents into a scintillation vial and send to the laboratory.
Vigorously and completely clean the cork borer between samples.
2.4 Shipment
Samples packed in glass vials must not touch or they might break in
shipment.
(a) Seal the samples with a sample seal over the end to guard
against tampering and to identify the sample.
(b) Package the bulk samples in separate packages from the air
samples. They may cross-contaminate each other and will invalidate the
results of the air samples.
(c) Include identifying paperwork with the samples, but not in
contact with the suspected asbestos.
(d) To maintain sample accountability, ship the samples by certified
mail, overnight express, or hand carry them to the laboratory.
[[Page 62]]
3. Analysis
The analysis of asbestos samples can be divided into two major
parts: sample preparation and microscopy. Because of the different
asbestos uses that may be encountered by the analyst, each sample may
need different preparation steps. The choices are outlined below. There
are several different tests that are performed to identify the asbestos
species and determine the percentage. They will be explained below.
3.1. Safety
(a) Do not create unnecessary dust. Handle the samples in HEPA-
filter equipped hoods. If samples are received in bags, envelopes or
other inappropriate container, open them only in a hood having a face
velocity at or greater than 100 fpm. Transfer a small amount to a
scintillation vial and only handle the smaller amount.
(b) Open samples in a hood, never in the open lab area.
(c) Index of refraction oils can be toxic. Take care not to get this
material on the skin. Wash immediately with soap and water if this
happens.
(d) Samples that have been heated in the muffle furnace or the
drying oven may be hot. Handle them with tongs until they are cool
enough to handle.
(e) Some of the solvents used, such as THF (tetrahydrofuran), are
toxic and should only be handled in an appropriate fume hood and
according to instructions given in the Material Safety Data Sheet
(MSDS).
3.2. Equipment
(a) Phase contrast microscope with 10x, 16x and 40x objectives, 10x
wide-field eyepieces, G-22 Walton-Beckett graticule, Whipple disk,
polarizer, analyzer and first order red or gypsum plate, 100 Watt
illuminator, rotating position condenser with oversize phase rings,
central stop dispersion objective, Kohler illumination and a rotating
mechanical stage.
(b) Stereo microscope with reflected light illumination, transmitted
light illumination, polarizer, analyzer and first order red or gypsum
plate, and rotating stage.
(c) Negative pressure hood for the stereo microscope
(d) Muffle furnace capable of 600 [deg]C
(e) Drying oven capable of 50-150 [deg]C
(f) Aluminum specimen pans
(g) Tongs for handling samples in the furnace
(h) High dispersion index of refraction oils (Special for dispersion
staining.)
n = 1.550
n = 1.585
n = 1.590
n = 1.605
n = 1.620
n = 1.670
n = 1.680
n = 1.690
(i) A set of index of refraction oils from about n=1.350 to n=2.000
in n=0.005 increments. (Standard for Becke line analysis.)
(j) Glass slides with painted or frosted ends 1x3 inches 1mm thick,
precleaned.
(k) Cover Slips 22x22 mm, 1\1/2\
(l) Paper clips or dissection needles
(m) Hand grinder
(n) Scalpel with both 10 and 11 blades
(o) 0.1 molar HCl
(p) Decalcifying solution (Baxter Scientific Products)
Ethylenediaminetetraacetic Acid,
Tetrasodium......................................................0.7 g/l
Sodium Potassium Tartrate...................................8.0 mg/liter
Hydrochloric Acid...........................................99.2 g/liter
Sodium Tartrate.............................................0.14 g/liter
(q) Tetrahydrofuran (THF)
(r) Hotplate capable of 60 [deg]C
(s) Balance
(t) Hacksaw blade
(u) Ruby mortar and pestle
3.3. Sample Pre-Preparation
Sample preparation begins with pre-preparation which may include
chemical reduction of the matrix, heating the sample to dryness or
heating in the muffle furnace. The end result is a sample which has been
reduced to a powder that is sufficiently fine to fit under the cover
slip. Analyze different phases of samples separately, e.g., tile and the
tile mastic should be analyzed separately as the mastic may contain
asbestos while the tile may not.
(a) Wet samples
Samples with a high water content will not give the proper
dispersion colors and must be dried prior to sample mounting. Remove the
lid of the scintillation vial, place the bottle in the drying oven and
heat at 100 [deg]C to dryness (usually about 2 h). Samples which are not
submitted to the lab in glass must be removed and placed in glass vials
or aluminum weighing pans before placing them in the drying oven.
(b) Samples With Organic Interference--Muffle Furnace
These may include samples with tar as a matrix, vinyl asbestos tile,
or any other organic that can be reduced by heating. Remove the sample
from the vial and weigh in a balance to determine the weight of the
submitted portion. Place the sample in a muffle furnace at 500 [deg]C
for 1 to 2 h or until all obvious organic material has been removed.
Retrieve, cool and weigh again to determine the weight loss on ignition.
This is necessary to determine the asbestos content of the submitted
sample, because the analyst will be looking at a reduced sample.
[[Page 63]]
Note: Heating above 600 [deg]C will cause the sample to undergo a
structural change which, given sufficient time, will convert the
chrysotile to forsterite. Heating even at lower temperatures for 1 to 2
h may have a measurable effect on the optical properties of the
minerals. If the analyst is unsure of what to expect, a sample of
standard asbestos should be heated to the same temperature for the same
length of time so that it can be examined for the proper interpretation.
(c) Samples With Organic Interference--THF
Vinyl asbestos tile is the most common material treated with this
solvent, although, substances containing tar will sometimes yield to
this treatment. Select a portion of the material and then grind it up if
possible. Weigh the sample and place it in a test tube. Add sufficient
THF to dissolve the organic matrix. This is usually about 4 to 5 mL.
Remember, THF is highly flammable. Filter the remaining material through
a tared silver membrane, dry and weigh to determine how much is left
after the solvent extraction. Further process the sample to remove
carbonate or mount directly.
(d) Samples With Carbonate Interference
Carbonate material is often found on fibers and sometimes must be
removed in order to perform dispersion microscopy. Weigh out a portion
of the material and place it in a test tube. Add a sufficient amount of
0.1 M HCl or decalcifying solution in the tube to react all the
carbonate as evidenced by gas formation; i.e., when the gas bubbles
stop, add a little more solution. If no more gas forms, the reaction is
complete. Filter the material out through a tared silver membrane, dry
and weigh to determine the weight lost.
3.4. Sample Preparation
Samples must be prepared so that accurate determination can be made
of the asbestos type and amount present. The following steps are carried
out in the low-flow hood (a low-flow hood has less than 50 fpm flow):
(1) If the sample has large lumps, is hard, or cannot be made to lie
under a cover slip, the grain size must be reduced. Place a small amount
between two slides and grind the material between them or grind a small
amount in a clean mortar and pestle. The choice of whether to use an
alumina, ruby, or diamond mortar depends on the hardness of the
material. Impact damage can alter the asbestos mineral if too much
mechanical shock occurs. (Freezer mills can completely destroy the
observable crystallinity of asbestos and should not be used). For some
samples, a portion of material can be shaved off with a scalpel, ground
off with a hand grinder or hack saw blade.
The preparation tools should either be disposable or cleaned
thoroughly. Use vigorous scrubbing to loosen the fibers during the
washing. Rinse the implements with copious amounts of water and air-dry
in a dust-free environment.
(2) If the sample is powder or has been reduced as in (1) above, it
is ready to mount. Place a glass slide on a piece of optical tissue and
write the identification on the painted or frosted end. Place two drops
of index of refraction medium n=1.550 on the slide. (The medium n=1.550
is chosen because it is the matching index for chrysotile. Dip the end
of a clean paper-clip or dissecting needle into the droplet of
refraction medium on the slide to moisten it. Then dip the probe into
the powder sample. Transfer what sticks on the probe to the slide. The
material on the end of the probe should have a diameter of about 3 mm
for a good mount. If the material is very fine, less sample may be
appropriate. For non-powder samples such as fiber mats, forceps should
be used to transfer a small amount of material to the slide. Stir the
material in the medium on the slide, spreading it out and making the
preparation as uniform as possible. Place a cover-slip on the
preparation by gently lowering onto the slide and allowing it to fall
``trapdoor'' fashion on the preparation to push out any bubbles. Press
gently on the cover slip to even out the distribution of particulate on
the slide. If there is insufficient mounting oil on the slide, one or
two drops may be placed near the edge of the coverslip on the slide.
Capillary action will draw the necessary amount of liquid into the
preparation. Remove excess oil with the point of a laboratory wiper.
Treat at least two different areas of each phase in this fashion.
Choose representative areas of the sample. It may be useful to select
particular areas or fibers for analysis. This is useful to identify
asbestos in severely inhomogeneous samples.
When it is determined that amphiboles may be present, repeat the
above process using the appropriate high-dispersion oils until an
identification is made or all six asbestos minerals have been ruled out.
Note that percent determination must be done in the index medium 1.550
because amphiboles tend to disappear in their matching mediums.
3.5. Analytical Procedure
Note: This method presumes some knowledge of mineralogy and optical
petrography.
The analysis consists of three parts: The determination of whether
there is asbestos present, what type is present and the determination of
how much is present. The general flow of the analysis is:
(1) Gross examination.
[[Page 64]]
(2) Examination under polarized light on the stereo microscope.
(3) Examination by phase-polar illumination on the compound phase
microscope.
(4) Determination of species by dispersion stain. Examination by
Becke line analysis may also be used; however, this is usually more
cumbersome for asbestos determination.
(5) Difficult samples may need to be analyzed by SEM or TEM, or the
results from those techniques combined with light microscopy for a
definitive identification. Identification of a particle as asbestos
requires that it be asbestiform. Description of particles should follow
the suggestion of Campbell. (Figure 1)
[[Page 65]]
[GRAPHIC] [TIFF OMITTED] TR10AU94.007
For the purpose of regulation, the mineral must be one of the six
minerals covered and must be in the asbestos growth habit. Large
specimen samples of asbestos generally have the gross appearance of
wood. Fibers are easily parted from it. Asbestos fibers are very long
compared with their widths. The fibers have a very high tensile strength
as demonstrated by bending without breaking. Asbestos fibers exist in
bundles that are easily parted, show longitudinal fine structure and may
be tufted at the ends showing ``bundle of sticks'' morphology. In the
microscope
[[Page 66]]
some of these properties may not be observable. Amphiboles do not always
show striations along their length even when they are asbestos. Neither
will they always show tufting. They generally do not show a curved
nature except for very long fibers. Asbestos and asbestiform minerals
are usually characterized in groups by extremely high aspect ratios
(greater than 100:1). While aspect ratio analysis is useful for
characterizing populations of fibers, it cannot be used to identify
individual fibers of intermediate to short aspect ratio. Observation of
many fibers is often necessary to determine whether a sample consists of
``cleavage fragments'' or of asbestos fibers.
Most cleavage fragments of the asbestos minerals are easily
distinguishable from true asbestos fibers. This is because true cleavage
fragments usually have larger diameters than 1 [micro]m. Internal
structure of particles larger than this usually shows them to have no
internal fibrillar structure. In addition, cleavage fragments of the
monoclinic amphiboles show inclined extinction under crossed polars with
no compensator. Asbestos fibers usually show extinction at zero degrees
or ambiguous extinction if any at all. Morphologically, the larger
cleavage fragments are obvious by their blunt or stepped ends showing
prismatic habit. Also, they tend to be acicular rather than filiform.
Where the particles are less than 1 [micro]m in diameter and have an
aspect ratio greater than or equal to 3:1, it is recommended that the
sample be analyzed by SEM or TEM if there is any question whether the
fibers are cleavage fragments or asbestiform particles.
Care must be taken when analyzing by electron microscopy because the
interferences are different from those in light microscopy and may
structurally be very similar to asbestos. The classic interference is
between anthophyllite and biopyribole or intermediate fiber. Use the
same morphological clues for electron microscopy as are used for light
microscopy, e.g. fibril splitting, internal longitudinal striation,
fraying, curvature, etc.
(1) Gross examination:
Examine the sample, preferably in the glass vial. Determine the
presence of any obvious fibrous component. Estimate a percentage based
on previous experience and current observation. Determine whether any
pre- preparation is necessary. Determine the number of phases present.
This step may be carried out or augmented by observation at 6 to 40x
under a stereo microscope.
(2) After performing any necessary pre-preparation, prepare slides
of each phase as described above. Two preparations of the same phase in
the same index medium can be made side-by-side on the same glass for
convenience. Examine with the polarizing stereo microscope. Estimate the
percentage of asbestos based on the amount of birefringent fiber
present.
(3) Examine the slides on the phase-polar microscopes at
magnifications of 160 and 400x. Note the morphology of the fibers. Long,
thin, very straight fibers with little curvature are indicative of
fibers from the amphibole family. Curved, wavy fibers are usually
indicative of chrysotile. Estimate the percentage of asbestos on the
phase-polar microscope under conditions of crossed polars and a gypsum
plate. Fibers smaller than 1.0 [micro]m in thickness must be identified
by inference to the presence of larger, identifiable fibers and
morphology. If no larger fibers are visible, electron microscopy should
be performed. At this point, only a tentative identification can be
made. Full identification must be made with dispersion microscopy.
Details of the tests are included in the appendices.
(4) Once fibers have been determined to be present, they must be
identified. Adjust the microscope for dispersion mode and observe the
fibers. The microscope has a rotating stage, one polarizing element, and
a system for generating dark-field dispersion microscopy (see Section
4.6. of this appendix). Align a fiber with its length parallel to the
polarizer and note the color of the Becke lines. Rotate the stage to
bring the fiber length perpendicular to the polarizer and note the
color. Repeat this process for every fiber or fiber bundle examined. The
colors must be consistent with the colors generated by standard asbestos
reference materials for a positive identification. In n=1.550,
amphiboles will generally show a yellow to straw-yellow color indicating
that the fiber indices of refraction are higher than the liquid. If
long, thin fibers are noted and the colors are yellow, prepare further
slides as above in the suggested matching liquids listed below:
------------------------------------------------------------------------
Type of asbestos Index of refraction
------------------------------------------------------------------------
Chrysotile.......................... n=1.550.
Amosite............................. n=1.670 or 1.680.
Crocidolite......................... n=1.690.
Anthophyllite....................... n=1.605 and 1.620.
Tremolite........................... n=1.605 and 1.620.
Actinolite.......................... n=1.620.
------------------------------------------------------------------------
Where more than one liquid is suggested, the first is preferred;
however, in some cases this liquid will not give good dispersion color.
Take care to avoid interferences in the other liquid; e.g., wollastonite
in n=1.620 will give the same colors as tremolite. In n=1.605
wollastonite will appear yellow in all directions. Wollastonite may be
determined under crossed polars as it will change from blue to yellow as
it is rotated along its fiber axis by tapping on the cover slip.
Asbestos minerals will not change in this way.
Determination of the angle of extinction may, when present, aid in
the determination
[[Page 67]]
of anthophyllite from tremolite. True asbestos fibers usually have
0[deg] extinction or ambiguous extinction, while cleavage fragments have
more definite extinction.
Continue analysis until both preparations have been examined and all
present species of asbestos are identified. If there are no fibers
present, or there is less than 0.1% present, end the analysis with the
minimum number of slides (2).
(5) Some fibers have a coating on them which makes dispersion
microscopy very difficult or impossible. Becke line analysis or electron
microscopy may be performed in those cases. Determine the percentage by
light microscopy. TEM analysis tends to overestimate the actual
percentage present.
(6) Percentage determination is an estimate of occluded area,
tempered by gross observation. Gross observation information is used to
make sure that the high magnification microscopy does not greatly over-
or under- estimate the amount of fiber present. This part of the
analysis requires a great deal of experience. Satisfactory models for
asbestos content analysis have not yet been developed, although some
models based on metallurgical grain-size determination have found some
utility. Estimation is more easily handled in situations where the grain
sizes visible at about 160x are about the same and the sample is
relatively homogeneous.
View all of the area under the cover slip to make the percentage
determination. View the fields while moving the stage, paying attention
to the clumps of material. These are not usually the best areas to
perform dispersion microscopy because of the interference from other
materials. But, they are the areas most likely to represent the accurate
percentage in the sample. Small amounts of asbestos require slower
scanning and more frequent analysis of individual fields.
Report the area occluded by asbestos as the concentration. This
estimate does not generally take into consideration the difference in
density of the different species present in the sample. For most samples
this is adequate. Simulation studies with similar materials must be
carried out to apply microvisual estimation for that purpose and is
beyond the scope of this procedure.
(7) Where successive concentrations have been made by chemical or
physical means, the amount reported is the percentage of the material in
the ``as submitted'' or original state. The percentage determined by
microscopy is multiplied by the fractions remaining after pre-
preparation steps to give the percentage in the original sample. For
example:
Step 1. 60% remains after heating at 550 [deg]C for 1 h.
Step 2. 30% of the residue of step 1 remains after dissolution of
carbonate in 0.1 m HCl.
Step 3. Microvisual estimation determines that 5% of the sample is
chrysotile asbestos.
The reported result is:
R=(Microvisual result in percent)x(Fraction remaining after step
2)x(Fraction remaining of original sample after step 1)
R=(5)x(.30)x(.60)=0.9%
(8) Report the percent and type of asbestos present. For samples
where asbestos was identified, but is less than 1.0%, report ``Asbestos
present, less than 1.0%.'' There must have been at least two observed
fibers or fiber bundles in the two preparations to be reported as
present. For samples where asbestos was not seen, report as ``None
Detected.''
4. Auxiliary Information
Because of the subjective nature of asbestos analysis, certain
concepts and procedures need to be discussed in more depth. This
information will help the analyst understand why some of the procedures
are carried out the way they are.
4.1. Light
Light is electromagnetic energy. It travels from its source in
packets called quanta. It is instructive to consider light as a plane
wave. The light has a direction of travel. Perpendicular to this and
mutually perpendicular to each other, are two vector components. One is
the magnetic vector and the other is the electric vector. We shall only
be concerned with the electric vector. In this description, the
interaction of the vector and the mineral will describe all the
observable phenomena. From a light source such a microscope illuminator,
light travels in all different direction from the filament.
In any given direction away from the filament, the electric vector
is perpendicular to the direction of travel of a light ray. While
perpendicular, its orientation is random about the travel axis. If the
electric vectors from all the light rays were lined up by passing the
light through a filter that would only let light rays with electric
vectors oriented in one direction pass, the light would then be
POLARIZED.
Polarized light interacts with matter in the direction of the
electric vector. This is the polarization direction. Using this property
it is possible to use polarized light to probe different materials and
identify them by how they interact with light.
The speed of light in a vacuum is a constant at about 2.99x10\8\ m/
s. When light travels in different materials such as air, water,
minerals or oil, it does not travel at this speed. It travels slower.
This slowing is a function of both the material through which the light
is traveling and the wavelength or frequency of the light. In general,
the more
[[Page 68]]
dense the material, the slower the light travels. Also, generally, the
higher the frequency, the slower the light will travel. The ratio of the
speed of light in a vacuum to that in a material is called the index of
refraction (n). It is usually measured at 589 nm (the sodium D line). If
white light (light containing all the visible wavelengths) travels
through a material, rays of longer wavelengths will travel faster than
those of shorter wavelengths, this separation is called dispersion.
Dispersion is used as an identifier of materials as described in Section
4.6.
4.2. Material Properties
Materials are either amorphous or crystalline. The difference
between these two descriptions depends on the positions of the atoms in
them. The atoms in amorphous materials are randomly arranged with no
long range order. An example of an amorphous material is glass. The
atoms in crystalline materials, on the other hand, are in regular arrays
and have long range order. Most of the atoms can be found in highly
predictable locations. Examples of crystalline material are salt, gold,
and the asbestos minerals.
It is beyond the scope of this method to describe the different
types of crystalline materials that can be found, or the full
description of the classes into which they can fall. However, some
general crystallography is provided below to give a foundation to the
procedures described.
With the exception of anthophyllite, all the asbestos minerals
belong to the monoclinic crystal type. The unit cell is the basic
repeating unit of the crystal and for monoclinic crystals can be
described as having three unequal sides, two 90[deg] angles and one
angle not equal to 90[deg]. The orthorhombic group, of which
anthophyllite is a member has three unequal sides and three 90[deg]
angles. The unequal sides are a consequence of the complexity of fitting
the different atoms into the unit cell. Although the atoms are in a
regular array, that array is not symmetrical in all directions. There is
long range order in the three major directions of the crystal. However,
the order is different in each of the three directions. This has the
effect that the index of refraction is different in each of the three
directions. Using polarized light, we can investigate the index of
refraction in each of the directions and identify the mineral or
material under investigation. The indices [alpha], [beta], and [gamma]
are used to identify the lowest, middle, and highest index of refraction
respectively. The x direction, associated with [alpha] is called the
fast axis. Conversely, the z direction is associated with [gamma] and is
the slow direction. Crocidolite has [alpha] along the fiber length
making it ``length-fast''. The remainder of the asbestos minerals have
the [gamma] axis along the fiber length. They are called ``length-
slow''. This orientation to fiber length is used to aid in the
identification of asbestos.
4.3. Polarized Light Technique
Polarized light microscopy as described in this section uses the
phase-polar microscope described in Section 3.2. A phase contrast
microscope is fitted with two polarizing elements, one below and one
above the sample. The polarizers have their polarization directions at
right angles to each other. Depending on the tests performed, there may
be a compensator between these two polarizing elements. Light emerging
from a polarizing element has its electric vector pointing in the
polarization direction of the element. The light will not be
subsequently transmitted through a second element set at a right angle
to the first element. Unless the light is altered as it passes from one
element to the other, there is no transmission of light.
4.4. Angle of Extinction
Crystals which have different crystal regularity in two or three
main directions are said to be anisotropic. They have a different index
of refraction in each of the main directions. When such a crystal is
inserted between the crossed polars, the field of view is no longer dark
but shows the crystal in color. The color depends on the properties of
the crystal. The light acts as if it travels through the crystal along
the optical axes. If a crystal optical axis were lined up along one of
the polarizing directions (either the polarizer or the analyzer) the
light would appear to travel only in that direction, and it would blink
out or go dark. The difference in degrees between the fiber direction
and the angle at which it blinks out is called the angle of extinction.
When this angle can be measured, it is useful in identifying the
mineral. The procedure for measuring the angle of extinction is to first
identify the polarization direction in the microscope. A commercial
alignment slide can be used to establish the polarization directions or
use anthophyllite or another suitable mineral. This mineral has a zero
degree angle of extinction and will go dark to extinction as it aligns
with the polarization directions. When a fiber of anthophyllite has gone
to extinction, align the eyepiece reticle or graticule with the fiber so
that there is a visual cue as to the direction of polarization in the
field of view. Tape or otherwise secure the eyepiece in this position so
it will not shift.
After the polarization direction has been identified in the field of
view, move the particle of interest to the center of the field of view
and align it with the polarization direction. For fibers, align the
fiber along this direction. Note the angular reading of the rotating
stage. Looking at the particle, rotate the stage until the fiber goes
dark or ``blinks
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out''. Again note the reading of the stage. The difference in the first
reading and the second is an angle of extinction.
The angle measured may vary as the orientation of the fiber changes
about its long axis. Tables of mineralogical data usually report the
maximum angle of extinction. Asbestos forming minerals, when they
exhibit an angle of extinction, usually do show an angle of extinction
close to the reported maximum, or as appropriate depending on the
substitution chemistry.
4.5. Crossed Polars with Compensator
When the optical axes of a crystal are not lined up along one of the
polarizing directions (either the polarizer or the analyzer) part of the
light travels along one axis and part travels along the other visible
axis. This is characteristic of birefringent materials.
The color depends on the difference of the two visible indices of
refraction and the thickness of the crystal. The maximum difference
available is the difference between the [alpha] and the [gamma] axes.
This maximum difference is usually tabulated as the birefringence of the
crystal.
For this test, align the fiber at 45[deg] to the polarization
directions in order to maximize the contribution to each of the optical
axes. The colors seen are called retardation colors. They arise from the
recombination of light which has traveled through the two separate
directions of the crystal. One of the rays is retarded behind the other
since the light in that direction travels slower. On recombination, some
of the colors which make up white light are enhanced by constructive
interference and some are suppressed by destructive interference. The
result is a color dependent on the difference between the indices and
the thickness of the crystal. The proper colors, thicknesses, and
retardations are shown on a Michel-Levy chart. The three items,
retardation, thickness and birefringence are related by the following
relationship:
R=t(n[gamma]--n[alpha])
R=retardation, t=crystal thickness in [micro]m, and
n[alpha],[gamma]=indices of refraction.
Examination of the equation for asbestos minerals reveals that the
visible colors for almost all common asbestos minerals and fiber sizes
are shades of gray and black. The eye is relatively poor at
discriminating different shades of gray. It is very good at
discriminating different colors. In order to compensate for the low
retardation, a compensator is added to the light train between the
polarization elements. The compensator used for this test is a gypsum
plate of known thickness and birefringence. Such a compensator when
oriented at 45[deg] to the polarizer direction, provides a retardation
of 530 nm of the 530 nm wavelength color. This enhances the red color
and gives the background a characteristic red to red-magenta color. If
this ``full-wave'' compensator is in place when the asbestos preparation
is inserted into the light train, the colors seen on the fibers are
quite different. Gypsum, like asbestos has a fast axis and a slow axis.
When a fiber is aligned with its fast axis in the same direction as the
fast axis of the gypsum plate, the ray vibrating in the slow direction
is retarded by both the asbestos and the gypsum. This results in a
higher retardation than would be present for either of the two minerals.
The color seen is a second order blue. When the fiber is rotated 90[deg]
using the rotating stage, the slow direction of the fiber is now aligned
with the fast direction of the gypsum and the fast direction of the
fiber is aligned with the slow direction of the gypsum. Thus, one ray
vibrates faster in the fast direction of the gypsum, and slower in the
slow direction of the fiber; the other ray will vibrate slower in the
slow direction of the gypsum and faster in the fast direction of the
fiber. In this case, the effect is subtractive and the color seen is a
first order yellow. As long as the fiber thickness does not add
appreciably to the color, the same basic colors will be seen for all
asbestos types except crocidolite. In crocidolite the colors will be
weaker, may be in the opposite directions, and will be altered by the
blue absorption color natural to crocidolite. Hundreds of other
materials will give the same colors as asbestos, and therefore, this
test is not definitive for asbestos. The test is useful in
discriminating against fiberglass or other amorphous fibers such as some
synthetic fibers. Certain synthetic fibers will show retardation colors
different than asbestos; however, there are some forms of polyethylene
and aramid which will show morphology and retardation colors similar to
asbestos minerals. This test must be supplemented with a positive
identification test when birefringent fibers are present which can not
be excluded by morphology. This test is relatively ineffective for use
on fibers less than 1 [micro]m in diameter. For positive confirmation
TEM or SEM should be used if no larger bundles or fibers are visible.
4.6. Dispersion Staining
Dispersion microscopy or dispersion staining is the method of choice
for the identification of asbestos in bulk materials. Becke line
analysis is used by some laboratories and yields the same results as
does dispersion staining for asbestos and can be used in lieu of
dispersion staining. Dispersion staining is performed on the same
platform as the phase-polar analysis with the analyzer and compensator
removed. One polarizing element remains to define the direction of the
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light so that the different indices of refraction of the fibers may be
separately determined. Dispersion microscopy is a dark-field technique
when used for asbestos. Particles are imaged with scattered light. Light
which is unscattered is blocked from reaching the eye either by the back
field image mask in a McCrone objective or a back field image mask in
the phase condenser. The most convenient method is to use the rotating
phase condenser to move an oversized phase ring into place. The ideal
size for this ring is for the central disk to be just larger than the
objective entry aperture as viewed in the back focal plane. The larger
the disk, the less scattered light reaches the eye. This will have the
effect of diminishing the intensity of dispersion color and will shift
the actual color seen. The colors seen vary even on microscopes from the
same manufacturer. This is due to the different bands of wavelength
exclusion by different mask sizes. The mask may either reside in the
condenser or in the objective back focal plane. It is imperative that
the analyst determine by experimentation with asbestos standards what
the appropriate colors should be for each asbestos type. The colors
depend also on the temperature of the preparation and the exact
chemistry of the asbestos. Therefore, some slight differences from the
standards should be allowed. This is not a serious problem for
commercial asbestos uses. This technique is used for identification of
the indices of refraction for fibers by recognition of color. There is
no direct numerical readout of the index of refraction. Correlation of
color to actual index of refraction is possible by referral to published
conversion tables. This is not necessary for the analysis of asbestos.
Recognition of appropriate colors along with the proper morphology are
deemed sufficient to identify the commercial asbestos minerals. Other
techniques including SEM, TEM, and XRD may be required to provide
additional information in order to identify other types of asbestos.
Make a preparation in the suspected matching high dispersion oil,
e.g., n=1.550 for chrysotile. Perform the preliminary tests to determine
whether the fibers are birefringent or not. Take note of the
morphological character. Wavy fibers are indicative of chrysotile while
long, straight, thin, frayed fibers are indicative of amphibole
asbestos. This can aid in the selection of the appropriate matching oil.
The microscope is set up and the polarization direction is noted as in
Section 4.4. Align a fiber with the polarization direction. Note the
color. This is the color parallel to the polarizer. Then rotate the
fiber rotating the stage 90[deg] so that the polarization direction is
across the fiber. This is the perpendicular position. Again note the
color. Both colors must be consistent with standard asbestos minerals in
the correct direction for a positive identification of asbestos. If only
one of the colors is correct while the other is not, the identification
is not positive. If the colors in both directions are bluish-white, the
analyst has chosen a matching index oil which is higher than the correct
matching oil, e.g. the analyst has used n=1.620 where chrysotile is
present. The next lower oil (Section 3.5.) should be used to prepare
another specimen. If the color in both directions is yellow-white to
straw-yellow-white, this indicates that the index of the oil is lower
than the index of the fiber, e.g. the preparation is in n=1.550 while
anthophyllite is present. Select the next higher oil (Section 3.5.) and
prepare another slide. Continue in this fashion until a positive
identification of all asbestos species present has been made or all
possible asbestos species have been ruled out by negative results in
this test. Certain plant fibers can have similar dispersion colors as
asbestos. Take care to note and evaluate the morphology of the fibers or
remove the plant fibers in pre- preparation. Coating material on the
fibers such as carbonate or vinyl may destroy the dispersion color.
Usually, there will be some outcropping of fiber which will show the
colors sufficient for identification. When this is not the case, treat
the sample as described in Section 3.3. and then perform dispersion
staining. Some samples will yield to Becke line analysis if they are
coated or electron microscopy can be used for identification.
5. References
5.1. Crane, D.T., Asbestos in Air, OSHA method ID160, Revised
November 1992.
5.2. Ford, W.E., Dana's Textbook of Mineralogy; Fourth Ed.; John
Wiley and Son, New York, 1950, p. vii.
5.3. Selikoff,.I.J., Lee, D.H.K., Asbestos and Disease, Academic
Press, New York, 1978, pp. 3,20.
5.4. Women Inspectors of Factories. Annual Report for 1898, H.M.
Statistical Office, London, p. 170 (1898).
5.5. Selikoff, I.J., Lee, D.H.K., Asbestos and Disease, Academic
Press, New York, 1978, pp. 26,30.
5.6. Campbell, W.J., et al, Selected Silicate Minerals and Their
Asbestiform Varieties, United States Department of the Interior, Bureau
of Mines, Information Circular 8751, 1977.
5.7. Asbestos, Code of Federal Regulations, 29 CFR 1910.1001 and 29
CFR 1926.58.
5.8. National Emission Standards for Hazardous Air Pollutants;
Asbestos NESHAP Revision, Federal Register, Vol. 55, No. 224, 20
November 1990, p. 48410.
5.9. Ross, M. The Asbestos Minerals: Definitions, Description, Modes
of Formation, Physical and Chemical Properties and Health Risk to the
Mining Community, Nation Bureau of Standards Special Publication,
Washington, DC, 1977.
[[Page 71]]
5.10. Lilis, R., Fibrous Zeolites and Endemic Mesothelioma in
Cappadocia, Turkey, J. Occ Medicine, 1981, 23,(8),548-550.
5.11. Occupational Exposure to Asbestos--1972, U.S. Department of
Health, Education and Welfare, Public Health Service, Center for Disease
Control, National Institute for Occupational Safety and Health, HSM-72-
10267.
5.12. Campbell, W.J., et al, Relationship of Mineral Habit to Size
Characteristics for Tremolite Fragments and Fibers, United States
Department of the Interior, Bureau of Mines, Information Circular 8367,
1979.
5.13. Mefford, D., DCM Laboratory, Denver, private communication,
July 1987.
5.14. Deer, W.A., Howie, R.A., Zussman, J., Rock Forming Minerals,
Longman, Thetford, UK, 1974.
5.15. Kerr, P.F., Optical Mineralogy; Third Ed. McGraw-Hill, New
York, 1959.
5.16. Veblen, D.R. (Ed.), Amphiboles and Other Hydrous Pyriboles--
Mineralogy, Reviews in Mineralogy, Vol 9A, Michigan, 1982, pp 1-102.
5.17. Dixon, W.C., Applications of Optical Microscopy in the
Analysis of Asbestos and Quartz, ACS Symposium Series, No. 120,
Analytical Techniques in Occupational Health Chemistry, 1979.
5.18. Polarized Light Microscopy, McCrone Research Institute,
Chicago, 1976.
5.19. Asbestos Identification, McCrone Research Institute, G & G
printers, Chicago, 1987.
5.20. McCrone, W.C., Calculation of Refractive Indices from
Dispersion Staining Data, The Microscope, No 37, Chicago, 1989.
5.21. Levadie, B. (Ed.), Asbestos and Other Health Related
Silicates, ASTM Technical Publication 834, ASTM, Philadelphia 1982.
5.22. Steel, E. and Wylie, A., Riordan, P.H. (Ed.), Mineralogical
Characteristics of Asbestos, Geology of Asbestos Deposits, pp. 93-101,
SME-AIME, 1981.
5.23. Zussman, J., The Mineralogy of Asbestos, Asbestos: Properties,
Applications and Hazards, pp. 45-67 Wiley, 1979.
[51 FR 22733, June 20, 1986, as amended at 51 FR 37004, Oct. 17, 1986;
52 FR 17754, 17755, May 12, 1987; 53 FR 35625, September 14, 1988; 54 FR
24334, June 7, 1989; 54 FR 29546, July 13, 1989; 54 FR 52027, Dec. 20,
1989, 55 FR 3731, Feb. 5, 1990; 55 FR 34710, Aug. 24, 1990; 57 FR 24330,
June 8, 1992; 59 FR 41057, Aug. 10, 1994; 60 FR 9625, Feb. 21, 1995; 60
FR 33344, June 28, 1995; 60 FR 33984-33987, June 29, 1995; 61 FR 5508,
Feb. 13, 1996; 61 FR 43457, Aug. 23, 1996; 63 FR 1285, Jan. 8, 1998; 70
FR 1141, Jan. 5, 2005; 71 FR 16672, 16673, Apr. 3, 2006]