§ 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 (µg/m ), 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 µg/m , as determined in accordance with appendix K to this part, is equal to or less than one.