By Jeryl L. Olson, Eric E. Boyd, and Craig B. Simonsen

The U.S. Environmental Protection Agency (EPA) will hold two public hearings on its proposed updates to the national ambient air quality standards (NAAQS) for fine particle pollution. 

Concerning the primary standards for fine particles (generally referring to particles less than or equal to 2.5 micrometers (mm) in diameter (PM2.5)), the EPA proposes to revise the annual PM2.5 standard by lowering the level to within a range of 12.0 to 13.0 micrograms per cubic meter (mg/m3) and to retain the 24-hour PM2.5 standard. With regard to the primary standard for particles generally less than or equal to 10 mm in diameter (PM10), the EPA proposes to retain the current 24-hour PM10 standard.

The hearings are scheduled for Philadelphia on July 17, 2012, and Sacramento on July 19, 2012. To register to speak at the hearings, contact Alan Rush at or 202-564-1658. EPA also will accept written comments on the proposed standards until August 31, 2012.