Sulfur oxides, respiratory toxicity

Upper respiratory toxicants include hydrogen halides (hydrogen chloride, hydrogen bromide), oxides (nitrogen oxides, sulfur oxides, sodium oxide), and hydroxides (ammonium hydroxide, sodium dusts, and potassium hydroxides). Lower respiratory toxicants include monomers (such as acrylonitrile), halides (fluorine, chlorine, bromine), and other miscellaneous... 

The Clean Air Act recognizes a number of so-called primary air pollutants, and the EPA has established standards for these substances. Ozone, nitrogen oxides, and sulfur dioxide are among these (the others are carbon monoxide and lead, discussed below, and total suspended particulates ). The EPA s standard for ozone is 0.08 parts of the gas per million parts of air (0.08 ppm), averaged over eight hours. Standards also exist for the oxides of sulfur and nitrogen. These are designed to prevent chronic respiratory toxicity of any kind. 

Sulfur Oxides and Oxoacids Sulfur dioxide, SO2, is a colorless, toxic gas with a characteristic suffocating odor. Its presence in polluted air (from the burning of fossil fuels) is known to cause respiratory ailments. The SO2 molecule has a bent geometry with a bond angle of 119.5°, very close to that predicted by the VSEPR model (Figure 22.45). 

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