Effect of near ambient exposures to sulfur dioxide and ferrous sulfate particles on murine pulmonary defense mechanisms.

An infectivity model was used to test the safety margins for presently established air quality standards for sulfur dioxide and sulfate particles. Mice and rats were exposed to atmospheres of sulfur dioxide and mono-disperse ferrous sulfate particles from 3 to 6 times the standard for 17 hr prior to, or 4 hr after infection with aerosols of Staphylococcus aureus or Group C Streptococci. Exposure to these concentrations of pollutants did not impair the rodents' ability to ingest and inactivate the minimally virulent Straphylococcus or enhance the virulence of the Group C Streptococci. Insofar as these results can be extrapolated to man, the present air quality standards for sulfur dioxide and sulfate particles are protective in regard to respiratory bacterial infection.