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 particulate matter. 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 public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.
EPA’s Office of Air and Radiation has requested CASAC review of its draft "Particulate Matter Policy Assessment." The purpose of the Policy Assessment is to “bridge the gap” between the scientific information and the judgments required of the Administrator in determining whether it is appropriate to retain or revise the particulate matter standards. The first draft Policy Assessment builds upon the key scientific and technical information contained in the Agency's Integrated Science Assessment for Particulate Matter (Final Report) (December 2009) as well as the two draft assessment documents titled Particulate Matter Urban-Focused Visibility Assessment: Second External Review Draft (January 2010) and Quantitative Health Risk Assessment for Particulate Matter: Second External Review Draft (February 2010).