The primary and secondary ambient air quality standards for particulate matter (PM) shall be as follows:

1. (a) For PM measured in the ambient air as particles having an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM10), the primary and secondary ambient air quality standards each shall be 150 micrograms per cubic meter (μg/m3), 24-hour average concentration; and

2. (b) For PM measured in the ambient air as particles having an aerodynamic diameter less than or equal to a nominal 2.5 micrometers in diameter or smaller (PM2.5):

   1. (1) The annual primary ambient air quality standards shall be 12.0 μg/m3, annual arithmetic mean concentration;
   2. (2) The annual secondary ambient air quality standards shall be 15.0 μg/m3, annual arithmetic mean concentration; and
   3. (3) The 24-hour primary and secondary ambient air quality standards each shall be 35 μg/m3, 24-hour average concentration.

Source. #120, eff 8-31-73; ss by #461, eff 4-20-74; ss by #1333, eff 4-1-79; ss by #1614, eff 7-30-80; ss by #1717, eff 2-19-81; ss by #2332, eff 4-29-83; ss by #2938, eff 12-27-84; ss by #4601, eff 4-21-89; ss by #5033, eff 12-27-90; ss by #6227, eff 4-25-96; ss by #8054, eff 2-28-04; ss by #10173, eff 9-1-12; ss by #13382, eff 5-25-22