High concentrations of sulfur dioxide (SO2) affect breathing and may aggravate existing respiratory and cardiovascular disease. Sensitive populations include asthmatics, individuals with bronchitis or emphysema, children and the elderly. SO2 is also a primary contributor to acid rain, which causes acidification of lakes and streams and can
damage trees, crops, historic buildings and statues. In addition, sulfur compounds in the air contribute to
visibility impairment in large parts of the country. This is especially noticeable in national parks.
Sulfur dioxide (SO2) is released primarily from burning fuels that contains sulfur (like coal, oil and diesel fuel). Stationary sources such as coal- and oil-fired power plants, steel mills, refineries, pulp and paper mills, and nonferrous smelters are the largest releasers.
NAAQS: 0.03 ppm (annual mean), 0.14 ppm (24-hr average) and 0.50 ppm (3-hr average)
More in Scorecard's chemical profile of sulfur dioxide.
VOLATILE ORGANIC COMPOUNDS (VOC)
Volatile organic compounds (VOC) are defined by the Clean Air Act as chemicals that participate in forming ozone (O3). Ozone is a respiratory toxicant. The class of VOCs includes many specific chemicals which may also cause adverse health effects in their own right (such as cancer or reproductive toxicity).
VOCs are emitted from diverse sources, including automobiles, chemical manufacturing facilities, drycleaners, paint shops and other commercial and residential sources that use solvent and paint. VOC emissions form O3 through complex chemical reactions with oxides of nitrogen (NOx) in the presence of sunlight.
More in Scorecard's chemical profile of volatile organic compounds.