Air Quality: EPA's Integrated Science Assessments (ISA)

EPA has set National Ambient Air Quality Standards (NAAQS) for six principal pollutants, which include: ozone, particulate matter, carbon monoxide, sulfur dioxide, nitrogen oxides, and lead. Called criteria pollutants, these are derived from numerous sources and are considered harmful to public health and the environment.

The Clean Air Act of 1970 established and requires periodic review of two types of standards that limit permissible amounts of the criteria pollutants. 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 against visibility impairment, damage to ecosystems and to animals, crops, vegetation, and buildings.

In particular, EPA's National Center for Environmental Assessment (NCEA) leads the effort to periodically review the science upon which the NAAQS are based by producing Integrated Science Assessments (ISA) [see Integrated Science Assessments (ISA) Legislative Requirements for more information] of these 6 pollutants. The ISA is a concise review, synthesis, and evaluation of the most policy-relevant science, and communicates critical science judgments relevant to the NAAQS review.

The ISA accurately reflects the latest scientific knowledge useful in indicating the kind and extent of identifiable effects on public health which may be expected from the presence of [a] pollutant in ambient air (Clean Air Act, Section 108, 2003). Key information and judgments formerly contained in the Air Quality Criteria Document (AQCD) for these assessments are incorporated in the new ISAs. Additional details of the pertinent scientific literature published since the last review, as well as selected older studies of particular interest, are included in a series of annexes at the ends of the reports. These ISA's (listed below) thus serves to update and revise the information available at the time of the previous final AQCD report.

The table below provides links to specific information about each criteria pollutant.

Listed are the Integrated Science Assessments (ISAs) for the NAAQS Review of:

Carbon Monoxide (CO) - 2000 (Final) Integrated Science Assessment for Carbon Monoxide - 2009 (Second External Review Draft) NAAQS: Carbon Monoxide (CO) Standards

Lead (Pb) - 2006 (Final) About Lead NAAQS: Lead (Pb) Standards

Ozone (O3) - 2006 (Final) About Ozone Primary Ozone (O3) - 2008 (workshop notice) NAAQS: Ozone (O3) Standards

Oxides of Nitrogen (NOx) (Primary - Health Criteria) - 2008 (Final) Oxides of Nitrogen & Sulfur (Secondary - Ecological Criteria) - 2008 (Final) NAAQS: Nitrogen Dioxide (NO2) Primary and Nitrogen Dioxide (NO2) Secondary Standards

Particulate Matter (PM) - 2004 (Final) About PM Integrated Science Assessment for Particulate Matter - 2009 (Second External Review Draft) NAAQS: Particulate Matter (PM) Standard

Sulfur Oxides (SO2) (Primary - Health Criteria) - 2008 (Final) Sulfur & Oxides of Nitrogen (Secondary - Ecological Criteria) - 2008 (Final) NAAQS: Sulfur Dioxide (SO2) Primary and Sulfur Dioxide (SO2) Secondary Standards

More information about air quality standards is available at the NAAQS Web site.

Additional Information