Ambient Standards

The federal
Clean Air Act established the National Ambient Air Quality Standards (NAAQS) for the six
principal pollutants (called “Criteria Pollutants”) to protect the publics health. Pennsylvania has adopted all of the NAAQS standards as well as several standards of it’s own. Pennsylvania
monitors the principal pollutants to ensure
attainment of these standards.

The Clean Air Act established two types of national air quality standards.

Primary standards set limits to protect public health, including the health of “sensitive” populations such as asthmatics, children, and the elderly.

Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.

National Ambient Air Quality Standards

PollutantAverageConcentration
Level
FormCarbon Monoxideprimary8-hour9 ppmNot to be exceeded more than once per year1-hour35 ppmLeadprimary and 
secondaryRolling 3 month average0.15 μg/m3 (1)Not to be exceededNitrogen Dioxideprimary1-hour100 ppb98th percentile, averaged over 3 yearsprimary and 
secondaryAnnual53 ppb (2)Annual MeanOzoneprimary and 
secondary8-hour0.075 ppm (3)Annual fourth-highest daily maximum 8-hr concentration, averaged over 3 yearsParticle PollutionPM2.5primaryAnnual12 μg/m3annual mean, averaged over 3 yearssecondaryAnnual15 μg/m3annual mean, averaged over 3 yearsprimary and 
secondary24-hour35 μg/m398th percentile, averaged over 3 yearsPM10primary and 
secondary24-hour150 μg/m3Not to be exceeded more than once per year on average over 3 yearsSulfur Dioxideprimary1-hour75 ppb (4)99th percentile of 1-hour daily maximum concentrations, averaged over 3 yearssecondary3-hour0.5 ppmNot to be exceeded more than once per year

As of December 2012

(1) Final rule signed October 15, 2008. The 1978 lead standard (1.5 µg/m3 as a quarterly average) remains in effect until one year after an area is designated for the 2008 standard, except that in areas designated nonattainment for the 1978, the 1978 standard remains in effect until implementation plans to attain or maintain the 2008 standard are approved.

(2) The official level of the annual NO2 standard is 0.053 ppm, equal to 53 ppb, which is shown here for the purpose of clearer comparison to the 1-hour standard.

(3) Final rule signed March 12, 2008. The 1997 ozone standard (0.08 ppm, annual fourth-highest daily maximum 8-hour concentration, averaged over 3 years) and related implementation rules remain in place. In 1997, EPA revoked the 1-hour ozone standard (0.12 ppm, not to be exceeded more than once per year) in all areas, although some areas have continued obligations under that standard (“anti-backsliding”). The 1-hour ozone standard is attained when the expected number of days per calendar year with maximum hourly average concentrations above 0.12 ppm is less than or equal to 1.

(4) Final rule signed June 2, 2010. The 1971 annual and 24-hour SO2 standards were revoked in that same rulemaking. However, these standards remain in effect until one year after an area is designated for the 2010 standard, except in areas designated nonattainment for the 1971 standards, where the 1971 standards remain in effect until implementation plans to attain or maintain the 2010 standard are approved.

Other Pa. Ambient Air Quality Standards

PollutantAverageConcentrationBeryllium30-Day0.01 ug/m3Fluorides24-Hour5 ug/m3Hydrogen Sulfide24-Hour 
1-Hour0.005 ppm 
0.1 ppm