PM10 National Ambient Air Quality Standards

The nation's air quality standards for particulate matter were first established in 1971 and were not significantly revised until 1987, when EPA established the PM₁₀ NAAQS, changing the indicator of the standards to regulate respirable particles less than or equal to 10 microns in diameter (about 1/7^th the average width of a human hair).

For more information regarding the PM₁₀ NAAQS see the EPA website.

• EPA Particulate Matter (PM) Basics