Health Effects of Radon

Did you know that radon is the second leading cause of lung cancer in the U.S.? The Environmental Protection Agency (EPA) estimates that over 21,000 lung cancer deaths in the U.S. each year are related to radon.

Radon gas decays into microscopic particles that can be inhaled into the lungs. Radon particles trapped in the lungs continue to breakdown, damaging the lung tissue during this decay process. This damage increases the risk of developing lung cancer. Among people who have never smoked, radon is the leading cause of lung cancer.

Radon also increases the chance of lung cancer in people that smoke. For those who are exposed to elevated indoor radon levels, people who smoke have up to 10 times the risk of developing lung cancer than people who have never smoked. The Massachusetts Environmental Public Health Tracking's (MA EPHT's) radon page features a radon risk table and a map of radon zones in Massachusetts.

Radon is a naturally occurring radioactive gas that is odorless, colorless, and tasteless. As a gas, radon can move through pathways in soil and rock formations.

How Does Radon Enter Homes?

  • Through cracks and crevices in the foundation floors and walls
  • Floor wall joints
  • Penetrations of utility lines and sump holes
  • Private water wells

Enclosed Spaces

Once inside an enclosed space, such as a home, radon can collect.

Most radon gas found in a home comes up from the ground, so the amount of radon is likely to be greater in the lowest levels of the home. Radon levels are usually higher in the wintertime because, during the heating season, warm air rises and escapes. This creates a vacuum in the lowest part of the house that causes the house to draw air, including radon, from below the home. Any equipment that exhausts air or requires venting can also contribute to the vacuum effect.


Testing the air in a home is the only way to know if indoor radon levels are elevated.

If you test your home in warm weather and get a low result, it is wise to test again during the heating season. If you have a private well, you should have your water tested for radon too.

For More Information

For information about testing your home for radon call the Massachusetts Department of Public Health (MDPH) Radon Unit. The EPA also has resources online: A Citizen's Guide to Radon and the Home Buyer's and Seller's Guide to Radon.