Return to Home Page

The 1997 and 2006 PM-2.5 Standards

There are presently 45 areas that violate the current PM-10 standard. The form of the PM-2.5 standard requires that the 3-year average (rounded to the nearest 0.1 ug/m3) of the annual means from single monitors or the average of multiple monitors must be at or below the level of the annual standard and the 3-year average (rounded to the nearest 1 ug/m3) of the ninety-eighth percentile values at each monitor cannot exceed the level of the daily standard. In determining attainment of the annual average standard, an area may choose to use either the spatially averaged concentrations across all population-oriented monitors or it may use the highest 3-year average based on individual monitors. The annual standard is 15 ug/m3. The 24-hour PM-2.5 standard announced in 1997 was 65 ug/m3.

On September 21, 2006, EPA announced that it revised the level of the 24-hour PM-2.5 standard to 35 micrograms per cubic meter (µg/m3) and retained the level of the annual PM-2.5 standard at 15 µg/m3. On October 8, 2009, the EPA announced the designations for nonattainment for the PM-2.5 2006 standard. The current number of areas that violate the PM-2.5 2006 standard is 32 and the number of counties that violate is currently 121. A map of the EPA's PM2.5 designations for nonattainment can be reviewed by clicking here.

Home Page | News | Corporation | Maps | Publications | Table of Contents | Multimedia Center

Copyright © 1995-2012 A.S.L. & Associates. All rights reserved.