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As of October 1, 2020, NLM will discontinue the Tox Town website, This change is part of NLM’s initiative to align and consolidate the Library’s consumer health information to make it easier for online health information seekers to find and navigate trusted health information from NLM.

We invite users to visit topics related to environmental health, safety, and toxicology on MedlinePlus, the NLM’s flagship website for health information for patients, families, and the general public. The National Institute of Environmental Health Sciences (NIEHS) also offers related resources that may be of interest: Kids Environment, Kids Health, Health & Education, and For Educators. If you have questions or suggestions, please contact NLM Customer Service.


What is Radon?

Radon is a radioactive, extremely toxic gas that is formed naturally from the decay of uranium or thorium in rocks and soil. It is more common in some areas of the country than others.

Radon comes in air through cracks and gaps in buildings and homes.

Radon levels may be used to predict earthquakes, study atmospheric transport, and explore for petroleum and uranium.

See also: Homes Mines Uranium Tailings Air Pollution Cancer

Where is Radon found?

  • Air – indoors and outdoors
  • Water – contaminated surface, well, and groundwater

How can I be exposed to Radon?

Radon commonly enter(s) the body through:


Ingestion (swallowing)

  • Drinking contaminated water

Inhalation (breathing)

  • Indoor or outdoor air, as gas or particles attached to dust

What happens when I am exposed to Radon?

Exposure to radon can cause:

  • Lung cancer
  • Emphysema
  • Damage to lung tissue

Who is at risk for exposure to Radon?

  • Cigarette smokers
    • Cigarette smokers have an increased chance of developing lung cancer.
  • Residents of areas rich in uranium or thorium 
    • More radon will be released by rocks and soil.

Reduce your risk

If you think your health has been affected by exposure to radon, 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 an area where the amount of uranium and thorium is high?
  • Have you tested your home for radon levels?
  • Do you use well water?
  • Visit the EPA web page on how to find a radon test kit and mitigation professional:
  • Test radon levels in your home with a professional radon test kit.
  • If radon levels are high, contact a professional radon mitigation firm that will seal the pathways where radon can enter the building, and install a ventilation system that routes air from underneath the home to the outdoors.
  • Contact your state radon office or a nationally certified professional radon testing and mitigation firm: American Association of Radon Scientists and Technologists, and National Radon Safety Board.

National Library of Medicine Resources and Databases

Additional Resources

  • Radon
    National Institute of Environmental Health Sciences
    Information on radon, its impacts on health, how to protect yourself, and links to additional resources, from a federal institute that investigates the interplay between environmental exposures, human biology, genetics, and common diseases to help prevent disease and improve human health.
  • What Is Radon?
    Navy and Marine Corps Public Health Center
    Resource on radon, including information about exposure, associated health effects, and how to protect your family from this radioactive gas.
  • Radon. ToxFAQs
    Agency for Toxic Substances and Disease Registry
    Factsheet with answers to the most frequently asked questions about radon exposure and its effect 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.
  • Radon
    Environmental Protection Agency
    Resources on radon for consumers, builders, and contractors, including information on its associated health risks, building and buying a safe home, action plans, and map of radon zones.
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