EPA stiffens particulate matter standards.

The U.S. Environmental Protection Agency (EPA) recently announced changes to the National Ambient Air Quality Standards (NAAQS) that address fine and coarse particulate matter (PM) limits for designating whether a state or regional entity is in compliance with the standards. The final role lowers by nearly half the level of fine particulates, those smaller than 2.5 microns, allowed in a designated area. The new standard allows for 35 micrograms of PM per cubic meter ([micro]g/[m.sup.3]) of air averaged over 24 hours, replacing the previous standard of 65 [micro]g/ [m.sup.3]. The agency also revoked the existing annual standard for coarse particles (those smaller than 10 microns).

The rule does not impact the standard for fine particles averaged on an annual basis, currently set at 15 [micro]g/[m.sup.3]. EPA also did not change the daily standard for coarse particles from the existing 150 [micro]g/[m.sup.3].

The Clean Air Act requires EPA to set NAAQS for six criteria pollutants, including particle pollution. Each state must develop a state implementation plan describing how it will attain and maintain the NAAQS. The new standards will be used to designate attainment (in compliance) and non-attainment (not in compliance) regions by November 2009. States then must meet the standards by April 2015 through a variety of possible mechanisms such as permits, emissions reductions plans and vehicle emissions limits.

For more information on this action and NAAQS for particulate matter, visit www. epa.gov/pm.