PM2.5 Average Values

In 2012, the United States Environmental Protection Agency (USEPA) established two complementary primary regulatory standards for PM_2.5.  The first is based on a yearly average value and is set at 12 micrograms per cubic meter, µg/m³, based on the average annual weighted mean value, averaged over 3 years.  The second standard is based on daily averages and is set at 35µg/m³ based on the 98th percentile of daily values, averaged over 3 years.  Any site whose 3-year average exceeds either of these values has failed to attain USEPA standards.  The design value is the actual value recorded at a given site used to demonstrate attainment of either of these standards. 

To view daily standard and annual design values by county, please select the desired time period below.