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Tox Town - Environmental health concerns and toxic chemicals where you live, work, and play
Sulfur Dioxideen español
Coal burning to make electricity is a major source of sulfur dioxide.

What is sulfur dioxide?

Sulfur dioxide is a colorless gas with a pungent and suffocating odor, similar to a just-struck match. It has an acidic taste and is a liquid when under pressure. Sulfur dioxide is formed when fuel containing sulfur, such as coal and oil, is burned. The chemical symbol for sulfur dioxide is SO2

Most sulfur dioxide in the air comes from the burning of coal and oil at electric power plants. Other sources of sulfur dioxide in the air are industrial facilities that use coal or oil, petroleum refineries, cement manufacturing, metal processing, paper pulp manufacturing, and copper smelting. Trains, large ships, and some diesel equipment burn high sulfur fuel, which releases sulfur dioxide into the air. It can also be released into the air from volcanic eruptions. 

Sulfur dioxide is used as a food preservative for some fruits and vegetables; as a disinfectant; for bleaching flour, fruit, grain, wood pulp, wool, textile fibers, wicker, gelatin, and glue; and for making other chemicals. It is also used in metal mining and refining, water treatment, and food processing. Sulfur dioxide and nitrogen oxides react with precipitation, oxygen, and other substances in the atmosphere to form acid rain.

How might I be exposed to sulfur dioxide?

Sulfur dioxide is a common air pollutant found in most of the air in the United States. You can be exposed to sulfur dioxide outdoors mainly by breathing air that contains it. You are most likely to be exposed to sulfur dioxide in the summer, when the sun and hot temperatures react with pollution to form smog, causing government officials to issue air quality alerts. You can also be exposed to sulfur dioxide through natural pollution sources, such as plant decay and volcanoes. 

Levels of sulfur dioxide in the air will be higher than normal near facilities that release sulfur dioxide through heavy industrial activities such as copper smelting or the burning or processing of coal and oil

You can be exposed to sulfur dioxide at work if you work in facilities that produce sulfur dioxide as a by-product, such as copper smelting plants and electric power plants. You can also be exposed if you work in the manufacturing of sulfuric acid, paper, food preservatives, or fertilizers.

How can sulfur dioxide affect my health?

Short-term exposure to high levels of sulfur dioxide in the air can be life-threatening by causing breathing difficulties and obstructing airways, especially for people with lung disease. Long-term exposure to persistent levels of sulfur dioxide can cause chronic bronchitis, emphysema, and respiratory illness. It can also aggravate existing heart disease. 

When sulfur dioxide reacts with other chemicals in the air to form tiny sulfate particles, these particles can gather in the lungs and cause increased respiratory problems and difficulty breathing. Long-term exposure to sulfate particles can cause respiratory disease and even premature death. 

Prolonged industrial exposure to sulfur dioxide may decrease fertility in men and women. 

Breathing sulfur dioxide can irritate the nose, throat, and lungs, and cause coughing and shortness of breath. Short-term exposure to sulfur dioxide can cause stomach pain, menstrual disorders, watery eyes, inhibition of thyroid function, loss of smell, headache, nausea, vomiting, fever, convulsions, and dizziness. 

At work, direct contact with sulfur dioxide as a gas can irritate and burn the skin and eyes, with possible eye damage. Direct contact with sulfur dioxide as a liquid can cause frostbite. The U.S. Occupational Safety and Health Administration has established safe levels of exposure to sulfur dioxide and standards for sampling air that might contain it.

Adults and children with asthma are sensitive to sulfur dioxide exposure, especially if they are active outdoors. Other people who are sensitive to sulfur dioxide are children, adults, and the elderly who have heart or lung disease.

For poisoning emergencies or questions about possible poisons, please contact your local poison control center at 1-800-222-1222.

This description is based on the information found in the Web links listed with this topic.


Web Links from MedlinePlus (National Library of Medicine)
Air Pollution

More Links
Acid Rain (Environmental Protection Agency)
Acid Rain Students Site (Environmental Protection Agency)
Map of Superfund Hazardous Waste Sites with Sulfur Dioxide in the United States. TOXMAP (National Library of Medicine)
Sulfur Dioxide (Environmental Protection Agency)
Sulfur Dioxide (Environmental Protection Agency)
Sulfur Dioxide. Haz-Map (National Library of Medicine)
Sulfur Dioxide. Hazardous Substances Data Bank (National Library of Medicine)
Sulfur Dioxide. ToxFAQs (Agency for Toxic Substances and Disease Registry)

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Last Updated: November 17, 2014

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