Air pollutant

Sulfur dioxide

Sulfur dioxide (SO2), a foul-smelling toxic gas, is part of a larger group of chemicals called sulfur oxides. These gases, especially SO2, are emitted by the burning of fossil fuels or other materials that contain sulfur.

Sulfur dioxide can damage trees and plants, inhibit plant growth, and damage sensitive ecosystems and waterways. It also can contribute to respiratory illness and aggravate existing heart and lung conditions.

Sources

SO2 is in emissions from power plants, metals processing and smelting facilities, and vehicles. Diesel vehicles and equipment were a major source of S02, but federal regulations to reduce the sulfur in diesel fuels has significantly lowered emissions. Like nitrogen dioxide, sulfur dioxide can create secondary pollutants, such as sulfate aerosols, particulate matter, and acid rain, once released into the air.

Human health and environmental concerns

Acid rain can damage trees and plants, inhibit plant growth, and damage sensitive ecosystems and waterways. Sulfur dioxide also contributes to the formation of thick haze and smog.

Sulfur dioxide contributes to respiratory illness by making breathing more difficult, especially for children, the elderly, and those with pre-existing conditions. Longer exposures can aggravate existing heart and lung conditions.

Monitoring, reporting, and regulations

Sulfur dioxide is one of six common air pollutants called criteria pollutants. Criteria pollutants are subject to primary and secondary National Ambient Air Quality Standards under the federal Clean Air Act. Primary standards define the air quality required to prevent adverse effects on human health; secondary standards are set to prevent adverse impacts on the environment.

Minnesota is currently in compliance with national standards for all six criteria pollutants.