Atmospheric sulfates as measured include a variety of chemical entities. Toxicological evidence indicates that certain sulfates, particularly fine particulate acid sulfates, are more potent respiratory irritants than sulfur dioxide alone. Preliminary epidemiological studies suggest that measured sulfates are associated with a variety of health indicators. Sulfates may also be related to damage to the environment by direct deposition or by formation of acid rain and can cause visibility deterioration. Although natural sulfur emissions are important on a global scale, sulfates in industrialized regions are largely produced by atmospheric reactions of manmade sulfur oxides emissions. Sulfates may be transported long distances from source areas and result in high ambient levels over broad regions. This is apparently the case in a 24 state region in the eastern U.S. Considerations of chemistry and transport suggest that reductions in regional SO2 emissions would produce reduction in sulfates, although the reductions would be less than one to one. This report summarizes current scientific and technical information concerning sulfates, and identifies needs for research and development. The report also discusses the implications of our current knowledge for present and long-term regulatory control of sulfur oxides, and presents and evaluates a policy for sulfates.

"EPA-450/2-75-007." "September 1975." Includes bibliographical references (pages 81-[85] ).