[Code of Federal Regulations]
[Title 40, Volume 2]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR50.6]

[Page 7]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 50--NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS--Table 
of Contents
 
Sec. 50.6   National primary and secondary ambient air quality standards for 
PM10.

    (a) The level of the national primary and secondary 24-hour ambient 
air quality standards for particulate matter is 150 micrograms per cubic 
meter ([mu]g/m\3\), 24-hour average concentration. The standards are 
attained when the expected number of days per calendar year with a 24-
hour average concentration above 150 [mu]g/m\3\, as determined in 
accordance with appendix K to this part, is equal to or less than one.
    (b) The level of the national primary and secondary annual standards 
for particulate matter is 50 micrograms per cubic meter ([mu]g/m\3\), 
annual arithmetic mean. The standards are attained when the expected 
annual arithmetic mean concentration, as determined in accordance with 
appendix K to this part, is less than or equal to 50 [mu]g/m\3\.
    (c) For the purpose of determining attainment of the primary and 
secondary standards, particulate matter shall be measured in the ambient 
air as PM10 (particles with an aerodynamic diameter less than 
or equal to a nominal 10 micrometers) by:
    (1) A reference method based on appendix J and designated in 
accordance with part 53 of this chapter, or
    (2) An equivalent method designated in accordance with part 53 of 
this chapter.

[52 FR 24663, July 1, 1987, as amended at 62 FR 38711, July 18, 1997; 65 
FR 80779, Dec. 22, 2000]