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Sulfur Dioxide

What is Sulfur Dioxide?

Sulfur dioxide, or SO2 is a colorless gas with a strong odor, similar to a just-struck match. It is formed when fuel containing sulfur, such as coal and oil, is burned, creating air pollution.

Most sulfur dioxide air pollution comes from the burning of coal and oil in power plants. It is also emitted by trains, large ships, and some diesel equipment that burns high sulfur fuel, and by volcanic eruptions.

Sulfur dioxide is used as a food preservative for some fruits and vegetables. It becomes a liquid under pressure.

Sulfur dioxide and nitrogen oxides affect the environment when they react with substances in the atmosphere to form acid rain.

See also: Factories Power Plants Air Pollution

Where is Sulfur Dioxide found?

  • Air – sulfur dioxide is a common air pollutant found in most of the country, especially in summer smog
  • Food – some fruits and vegetables are treated with sulfur dioxide

How can I be exposed to Sulfur Dioxide?

Sulfur Dioxide commonly enter(s) the body through:


Ingestion (swallowing)

  • Eating food preserved with sulfur dioxide

Inhalation (breathing)

  • Breathing sulfur dioxide polluted air, emissions from volcanoes

Skin contact

  • Touching liquid sulfur dioxide

What happens when I am exposed to Sulfur Dioxide?

Short-term health effects:
Breathing in sulfur dioxide can cause:

  • Burning of the nose, throat, and lungs
  • Difficulty breathing
  • Harm to the respiratory system

Exposure to very high levels of sulfur dioxide can be toxic and life-threatening.

Touching liquid sulfur dioxide can cause:

  • Frostbite
  • Irritation of the eyes

Long-term health effects:
Long-term exposure to sulfur dioxide can cause:

  • Changes in lung function
  • Decreased fertility in women and men
  • Loss of smell
  • Headache and dizziness
  • Nausea and vomiting
  • Bronchitis and shortness of breath

Who is at risk for exposure to Sulfur Dioxide?

  • Children and the elderly
    • These populations are particularly sensitive to exposure to sulfur dioxide.
  • People with asthma, heart, or lung disease
    • These populations are particularly sensitive to exposure to sulfur dioxide, especially if they are outdoors.

Reduce your risk

If you think your health has been affected by exposure to sulfur dioxide, contact your health care professional. 

Always wash your hands thoroughly after handling chemicals. For poisoning emergencies or questions about possible poisons, please contact your local poison control center at 1-800-222-1222.

  • Do you live in a high air pollution area or an area with a smog problem?
  • Do you live near a power plant that burns coal or oil?
  • Do you live in a heavily industrialized area?
  • Do you live near an active volcano?
  • If you live in a heavily industrialized area where sulfur dioxide emissions occur, limit outdoor activities during times of high air pollution to avoid breathing sulfur dioxide.
  • Monitor news bulletins and air pollution advisories to limit the amount of your exposure to sulfur dioxide.
  • If you have respiratory difficulties, pay close attention to these warnings.
  • Asthmatic children’s outdoor exercise should be limited when levels of sulfur dioxide are high.

National Library of Medicine Resources and Databases

Additional Resources

  • Sulfur Dioxide. ToxFAQs
    Agency for Toxic Substances and Disease Registry
    Factsheet with answers to the most frequently asked questions about sulfur dioxide exposure and its effects on human health, developed by a federal public health agency that protects communities from harmful health effects related to exposure to natural and man-made hazardous substances.
  • Sulfur Dioxide (SO2) Pollution
    Environmental Protection Agency
    Information on sulfur dioxide pollution, including sources of sulfur dioxide and health effects, as well as setting, reviewing, and implementing standards to reduce sulfur dioxide in the environment.
  • Air Trends: Sulfur Dioxide
    Alliance for Climate Education
    Data and interactive charts on national and regional trends in sulfur dioxide air pollution levels from 1980-2017.
  • Acid Rain
    Environmental Protection Agency
    Educational resources for students and teachers on acid rain, as well as information on its effects, and programs and policies aimed at reducing its harm on the environment.
  • Acid Rain Students Site
    Environmental Protection Agency
    A student website on the causes and effects of acid rain. The English and Spanish website includes games, activities, animation, and information on reducing pollutants.
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