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Division of Environmental and Community Health

Maine Center for Disease Control & Prevention

A Division of the Maine Department of Health and Human Services

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Radon in Drinking Water

Radon in Drinking Water

 


Page Index

Maximum Exposure Guidelines

Health Concerns

Mitigation

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Radon is an odorless, invisible, radioactive gas naturally released from rocks, soil, and water. While radon can enter buildings through small cracks or holes and build up in the air, it can also be introduced through well water. Radon that enters a building via the well water does so when the water is agitated, thus releasing the radon gas. Over time, exposure to high levels of radon can cause serious health problems including lung cancer.

 

Maximum Exposure Guidelines

  • In Maine, the Maximum Exposure Guideline (MEG) for radon in water is 4,000 picocuries* per liter (pCi/L).
  • EPA recommends radon mitigation if the indoor atmospheric radon level is at or above 4 picocuries per liter of air.

*A “picocurie" is a common unit for measuring the amount of radioactivity.

 

Health Concerns

Radon enters the body either by ingestion or inhalation. With every sip of water that contains radon, a radiation dose is delivered to internal organs; when radon gas is inhaled, a radiation dose is delivered to the surrounding lung tissue. While the primary health concern with radon is the risk of lung cancer, radon that is ingested in water may also pose a cancer risk in the stomach. The MEG for radon has been derived in consideration of both pathways of radon exposure.

The U.S. Environmental Protection Agency (EPA) has found radon exposure to be a leading cause of lung cancer deaths in this country. Their estimates suggest there are more than 20,000 radon-related lung cancer deaths in the United States every year, making it second only to cigarette smoke.

 

Mitigation

Before considering mitigation – or treatment – options for radon in water or air, the total risk (i.e., radon in air and water combined) should be assessed through testing. When radon levels in drinking water reach 4,000 pCi/l or higher, property owners are urged to consider mitigation. Once the radon in water level approaches 10,000 pCi/l, installing treatment becomes critical.

If you have tested your building and results are near or above these levels, mitigation guidance is available from the Maine CDC’s Radiation Control Program: visit online, phone 1-800-232-0842, or e-mail radon.dhhs@maine.gov.

IMPORTANT:  In Maine, only the property owner/occupant or a registered Mitigation Contractor may lawfully test for radon or install a radon mitigation system.

 

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Updated 2/22/2024