that sulfur dioxide by itself is incapable of producing an acute response in man even at concentrations considerably higher than 0.03 ppm.

This apparent discrepancy between epidemiologic observation and the results of controlled experiments is explainable by the presence in polluted air of sulfur dioxide oxidation products (such as sulfuric acid and particulate sulfates), which are potentially more toxic, and possibly by the synergistic effects of sulfur dioxide and other pollutants, including particles and ozone, within the respiratory system. It would therefore be inappropriate to use the failure to observe a human response to sulfur dioxide during controlled exposure as a reason to allow an increase in the emission of sulfur dioxide.

The literature concerning the health effects of sulfur oxides has recently been reviewed by scientific panels in the United States and elsewhere (NAS 1974, Rall 1974, Holland 1972, y NATO 1972). Those reviews have generally been organized by scientific subdiscipline, which provides a useful framework for consideration of specific points and integration of available information. They have been prepared by competent and thorough panels and are in the public record. The present document is organized by human disease processes that are believed to be related to the effects of sulfur oxides, and both animal experiments and controlled human exposures will be discussed according to disease process. It is hoped that this format will prove more intelligible to nonscientists, particularly those involved in decisions concerning clean air strategy.

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