National Ambient Air Quality Standards - Kentucky Energy and Environment Cabinet

Protecting Clean Air

The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (NAAQS - pronounced "nacks") for pollutants considered harmful to public health and the environment. The Clean Air Act identifies two types of standards for ambient (outdoor) air:

A primary standard, designed to protect public health
A secondary standard, designed to protect public welfare. Welfare includes damage to plants and animals, impairment of visibility, and property damage.

National Ambient Air Quality Standards
Pollutant	Average	Primary Standard	Secondary Standard
Carbon Monoxide	8-hour average	9 ppm	same as primary
Carbon Monoxide	1-hour	35 ppm	same as primary
Sulfur Dioxide	1-hour	75 ppb	same as primary
Sulfur Dioxide	3-hour	none	0.50 ppm
Nitrogen Dioxide	Annual	53 ppb	same as primary
Nitrogen Dioxide	1-hour	100 ppb	same as primary
Lead	Rolling 3-month average	0.15 ug/m3	same as primary
Ozone	8-hour average	0.070 ppm	same as primary
PM10	24-hour average	150 ug/m3	same as primary
PM2.5	24-hour average	35 ug/m3	same as primary
PM2.5	Annual average	12 ug/m3	15 ug/m3

Criteria Pollutants (EPA)Learn how EPA sets air quality standards, determines whether areas meet the standards, and works with areas to attain and maintain the standards.