Current toxicological information as the basis for sulfur oxide standards

The ambient air quality standard established in 1973 is 0.03 ppm annual average for sulfur dioxide and 0.075 mg/ m3for particulates. It is now generally believed that the toxicity of sulfur oxides in ambient air is significantly influenced by the coincident presence of particulates. Inhalation of 1 ppm of sulfur dioxide for 2 hr may produce alterations in pulmonary ventilatory function, both in normal and asthmatic subjects. Effects obtained at 0.5 ppm of sulfur dioxide are controversial and of questionable biological significance. No clear evidence exists that sulfur dioxide or bisulfite causes mutagenicity in mammals, and it is concluded from a variety of animal experiments that long-term exposure to sulfur dioxide alone does not cause cancer.