ABSTRACT
INTRODUCTION AND BACKGROUND Sulfur dioxide (SO2) is one of the six air contaminants regulated as “criteria “ pollutants by the Environmental Protection Agency. The criteria pollutants are ones that are widespread and relatively toxic. SO2 is emitted from both natural sources, such as volcanoes, and man-made sources. The most common source of SO2 emissions in the United States is coal-fired power plants. Other stationery sources of SO2 are refineries, smelters, paper and pulp mills, and food processing plants. A small amount of SO2 is emitted from the mobile fleet of vehicles. SO2 has been an air pollutant of concern for human populations for centuries. It was one of the air pollutants strongly associated with mortality during the London Killer Fog in December 1952. Approximately 20,000 premature deaths were associated with SO2 and black smoke during and in the month after that episode. In addition being a health threat itself, SO2 is the precursor of sulfuric acid (H2SO4), a pollutant prominent in acid rain and a fine particulate matter.
