U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment
This draft Integrated Science Assessment (ISA) represents a concise synthesis and evaluation of the most policy-relevant science and will ultimately provide the scientific bases for EPA’s decision on retaining or revising the current secondary standards for NO2, SO2, PM2.5 and PM10 since the prior release of the final assessment. The draft ISA was prepared as part of the review of the secondary (welfare-based) National Ambient Air Quality Standards (NAAQS) for oxides of nitrogen, oxides of sulfur, and particulate matter. The ISA, in conjunction with additional technical and policy assessments, provides the scientific basis for EPA’s decisions on the adequacy of the current NAAQS and the appropriateness of possible alternative standards.
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 ISA, in conjunction with additional technical and policy assessments, provides the scientific basis for EPA’s decisions on the adequacy of the current NAAQS and the appropriateness of possible alternative standards. The intent of the ISA, as described in the Clean Air Act, 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 AQCDs 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 last oxides of nitrogen and oxides of sulfur ISA which was published in 2008 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.