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 and oxides of sulfur. 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 First External Review Draft of its Integrated Science Assessment for Oxides of Nitrogen and Sulfur & Welfare Criteria. The final Integrated Science Assessment is intended to provide a synthesis and evaluation of science relevant for reviewing and revising the secondary (welfare-based) standard for the Nitrogen Dioxide and Sulfur Dioxide NAAQS.
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