Populations particularly sensitive to SO 2 include children, older adults, asthmatics and people with chronic lung disease.
Most sulfur dioxide comes from the combustion of oil and coal.
Sulfur dioxide air quality in Indiana has improved dramatically. All areas of Indiana currently meet federal health standards for sulfur dioxide. Indiana's annual SO 2 emissions from coal-fired power plants have fallen from more than 1.5 million tons in 1980 to approximately 0.5 million tons in 1996. Coal-fired power plants produced 90 percent of Indiana's sulfur dioxide emissions during 1995. Many Indiana power plants have recently greatly reduced sulfur dioxide emissions through strategies that include large capital investments in scrubbers, use of low-sulfur coal and optimal use of lower polluting boilers.