US EPA

The Integrated Science Assessment (ISA) for Oxides of Nitrogen, Oxides of Sulfur and Particulate Matter Ecological Criteria is a comprehensive evaluation and synthesis of the most policy relevant science aimed at characterizing the ecological effects caused by oxides of nitrogen, oxides of sulfur, and particulate matter. The ISA provides the scientific foundation necessary for the review of ecological effects associated with the secondary (welfare based) National Ambient Air Quality Standards (NAAQS) for these three criteria pollutants under the Clean Air Act. Welfare effects according to the Clean Air Act include, but are not limited to, effects on soils, water, crops, vegetation, animals, wildlife and climate.

Oxides of nitrogen, oxides of sulfur, and particulate matter are three of six criteria pollutants for which EPA has established NAAQS. Periodically, EPA reviews the scientific basis for these standards by preparing an ISA (formerly called an Air Quality Criteria Document). The intent of the ISA, as described in the Clean Air Act (CAA), is to 'accurately reflect the latest scientific knowledge expected from the presence of [a] pollutant in ambient air.' It includes scientific research from atmospheric sciences, exposure and deposition, biogeochemistry, hydrology, soil science, marine science, plant physiology, animal physiology, and ecology conducted at multiple scales (e.g., population, community, ecosystem, landscape levels).

Key information and judgments formerly found in the Air Quality Criteria Documents for oxides of sulfur, oxides of nitrogen and particulate matter for ecological effects are included; appendices provide additional details supporting the ISA. Together, the ISA and appendices serve to update and revise the 2008 Integrated Science Assessment for Oxides of Nitrogen and Oxides of Sulfur - Ecological Criteria and the ecological portion of the last particulate matter ISA which was published in 2009.

Additionally, the Clean Air Scientific Advisory Committee (CASAC) is an independent science advisory committee whose review and advisory functions are mandated by Section 109(d)(2) of the Clean Air Act, and charged (among other things) with performing an independent scientific review of all the EPA’s air quality criteria.

The purpose of the ISA, according to the CAA, is to “accurately reflect the latest scientific knowledge expected from the presence of [a] pollutant in ambient air” (U.S. Code, 1970a, 1970b). It includes scientific research from atmospheric sciences, exposure and deposition, biogeochemistry, hydrology, soil science, marine science, plant physiology, animal physiology, and ecology conducted at multiple scales (e.g., population, community, ecosystem, landscape levels).

U.S. EPA. Integrated Science Assessment (ISA) for Oxides of Nitrogen, Oxides of Sulfur and Particulate Matter Ecological Criteria (Final Report, 2020). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-20/278, 2020.