Frequent Questions

Why is radon in drinking water a health concern?

Radon gas decays into radioactive particles that can get trapped in your lungs when you breathe it.  As they break down further, these particles release small bursts of energy.  This can damage lung tissue and increase the chances of developing lung cancer over the course of a lifetime.  People who smoke have an even greater risk.  Not everyone exposed to high levels of radon will develop lung cancer.  However, radon in indoor air is the second leading cause of lung cancer.  About 20,000 deaths a year in the U.S. are caused by breathing radon in indoor air.  Only about 1-2 percent of radon in the air comes from drinking water. However breathing radon released to air from tap water increases the risk of lung cancer over the course of your lifetime.  Some radon stays in the water; drinking water containing radon also presents a risk of developing internal organ cancers, primarily stomach cancer.  However this risk is smaller than the risk of developing lung cancer from radon released to air from tap water.  Based on a National Academy of Sciences report, EPA estimates that radon in drinking water causes about 168 cancer deaths per year: 89% from lung cancer caused by breathing radon released to the indoor air from water and 11% from stomach cancer caused by consuming water containing radon.  Additional information on radon in drinking is available at

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