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Radon Lessons: What Watras Taught Us

Ways Radon Can Enter the Home. The image shows the inside of a home — bathroom, living room, kitchen, and basement. Red arrows show radon entry pathways. Radon sources include radon gas from soil and radon in well water. Radon can enter a home through a sump pump pit, floor-wall joints, floor cracks, and exposed soil in a crawlspace. Radon gas entering at the lowest level of the home can move to other areas. Radon from well water can enter a home through water taps, showers, dishwashers, and washers. Reducing the Risk from Radon: Information and Interventions A Guide for Health Care Providers. Publication No. E-18-2.

Radon is a radioactive gas that comes naturally from soil and rocks.  It moves through the ground and may enter the home through cracks in basement floors, wall joints, and well water. Long-term exposure to radon can cause lung cancer. For many years, radon was only considered a problem for people who worked in mines. Our understanding of radon changed in the 1980s after the discovery of radon in the home of Stanley Watras.

Stanley Watras was an engineer at a nuclear power plant being constructed in eastern Pennsylvania. At the time, exposure to radiation from the plant was not possible because no radioactive sources were on the building site. Yet when Watras would enter or leave the plant, radiation alarms would go off, sensing high radiation levels on Watras.

The Pennsylvania Public Health Department and the United States Environmental Protection Agency (EPA) teamed up to look into this very unusual case. They discovered high levels of radon in Watras' home. The radon was coming from rocks under his home that contained large amounts of uranium. Uranium was breaking down into radon, entering his home, and accumulating indoors at very high levels.

The image shows three homes in light blue and one larger home in orange, with a message that 1 out of 4 homes in Massachusetts have high radon levels.

Scientists looked for radon in other homes in Watras' neighborhood. Although the average radon level in Watras’ home was very high — over 2,500 picocuries per liter (pCi/L) — some of his neighbors had much lower levels. Scientists found that radon levels can be very different in houses that are right next to each other.

Two years after discovering radon in Watras' home, the EPA set an action level 4 pCi/L for radon in indoor air. In homes with a radon level greater than 4 pCi/L, homeowners should act to lower the level. The EPA also recommends action to lower radon levels if your home’s radon level is between 2 and 4 pCi/L. The lower the radon level, the lower the risk of developing lung cancer. You can fix a radon problem by contacting a certified radon mitigator who can install a radon fan mitigation system under your home that draws radon away from your home.

Radon can cause lung cancer.
Protect your family.

  • Test your home with a radon test kit. It's easy and inexpensive.
  • Fix your house if it has a high radon level.

MA Radon Hotline: (800) 723-6695

The EPA estimates that there are 628 radon-related cases of lung cancer in Massachusetts every year. Radon is the second leading cause of lung cancer after tobacco use. While radon is the leading cause of lung cancer among non-smokers, the risk of lung cancer from radon exposure is much greater for people who smoke.

You cannot see, taste, or smell radon, so the only way to know the radon level in your home is to test for it. You can learn about testing your home for radon by:


Testing for radon is easy, so don’t put off testing your home.

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