Under the Clean Air Act, EPA is required to carry out a periodic review and revision, as appropriate, of the air quality criteria and the primary and secondary standards for six criteria air pollutants, which include oxides of nitrogen, oxides of sulfur, and particulate matter. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.EPA's Office of Research and Development has requested a peer review of the Second External Review Draft of its Integrated Science Assessment for Oxides of Nitrogen, Oxides of Sulfur, and Particulate Matter & Ecological Criteria. The final Integrated Science Assessment is intended to provide a synthesis and evaluation of science relevent for reviewing and revising the secondary (welfare-based) standard for Oxides of Nitrogen, Oxides of Sulfur, and Particulate Matter NAAQS.
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