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Sulfur Dioxide Pollution

Sulfur Dioxide Pollution

What is Sulfur Dioxide?
Sulfur Dioxide (SO₂) is a colorless, reactive gas. It is produced when sulfur-containing fuels such as coal and oil are burned, during the smelting of metal, and by other industrial processes. It can also enter the atmosphere naturally when volcanos erupt, and as sulfate particles from ocean spray. Generally, the highest concentrations of SO₂ are found near large industrial sources. High concentrations of this pollutant are not usually found in the United States. SO₂ causes rain to become acidic, and it reduces visibility by creating haze (smog).

The Environmental Protection Agency uses its Air Quality Index to provide general information to the public about air quality and associated health effects. An Air Quality Index (AQI) of 100 for any pollutant corresponds to the level needed to violate the federal health standard for that pollutant. For sulfur dioxide, an AQI of 100 corresponds to 0.14 parts per million (ppm) over a 24-hour period -- the current federal standard.

Sulfur Dioxide Health Hazards

EPA Air Quality Index	Levels of Health Concern	Cautionary Statements
0 - 50	Good	None
51 - 100		None
101 - 150	Unhealthy for Sensitive Groups	People with asthma should consider limiting outdoor exertion.
151 - 200	Unhealthy	Children, asthmatics, and people with heart or lung disease should limit outdoor exertion.
201 - 300	Very Unhealthy	Children, asthmatics, and people with heart or lung disease should avoid outdoor exertion; everyone else should limit outdoor exertion.
301 - 500	Hazardous	Children, asthmatics, and people with heart or lung disease should remain indoors; everyone else should avoid outdoor exertion.

What are the health effects from Sulfur Dioxide?

Children and adults with asthma who are active outdoors are most vulnerable to the health effects of SO₂. The primary effect they experience, even with a brief exposure, is a narrowing of the airways, which may cause symptoms such as wheezing, chest tightness, and shortness of breath. Symptoms increase as SO₂ concentrations and/or breathing rates increase. When exposure ceases, lung function typically returns to normal within an hour.
At very high concentrations, SO₂ may cause wheezing, chest tightness, and shortness of breath in people who do not have asthma.
Long-term exposure to both SO₂ and fine particles can cause respiratory illness, alter the lung's defense mechanisms, and aggravate existing cardiovascular disease. People who may be most susceptible to these effects include individuals with cardiovascular disease or chronic lung disease, as well as children and the elderly.

For detailed information about real-time pollution levels in the U.S., visit the Environmental Protection Agency's Website.

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