Sulfur dioxide is a colorless, reactive gas produced during burning of sulfur-containing fuels such as coal and oil, during metal smelting, and by other industrial processes. Sulfur dioxide emitted to the atmosphere results largely from stationary sources such as coal and oil combustion, steel mills, refineries, pulp and paper mills, and nonferrous smelters. Generally, the highest concentrations of this criteria pollutant are found near large industrial sources, such as power plants and industrial boilers.
Health Impacts of Exposure
High concentrations of sulfur dioxide affect breathing and may aggravate existing respiratory and cardiovascular disease. Sensitive populations include asthmatics, individuals with bronchitis or emphysema, children, and the elderly. Sulfur dioxide is also a primary contributor to acid rain, which causes acidification of lakes and streams and can damage trees, crops, 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.