One of the leading causes of lung cancer is exposure to a colorless, odorless, tasteless gas that is especially prevalent in Pennsylvania.
Radon accounts for more than half of all human radiation exposure. For people who don't smoke, radon is the top cause of lung cancer, and for people who smoke, radon is the second-leading cause, according to the Environmental Protection Agency.
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Radium, uranium and other chemical elements — often present in soil and water —decay into radon, and the gas seeps from the bedrock underneath structures into enclosed homes and buildings through cracks and other openings. Outside, radon dilutes into the air, but inside it collects, emitting radioactive particles that people breathe in, causing lung damage, according to the International Atomic Energy Agency. Radon levels in homes tend to be highest during cold months, when doors and windows stay closed.
Due to Pennsylvania's unique geology and high levels of uranium in the soil, 40% of homes in the state have radon levels higher than the EPA recommends. In New Jersey, radon is present at dangerous levels in about 10% of homes. Nationwide, about 1 in 5 homes have dangerous radon levels, the EPA says.
The EPA considers most Pennsylvania counties – including Bucks, Chester, Delaware and Montgomery – to be among those with the highest potential for dangerous radon levels. The threat in Philadelphia is low, but the EPA urges all homes to be tested. In South Jersey, Camden, Burlington and Gloucester counties are considered medium risk.
More than 40 years of research has established the link between radon and lung cancer – an elevated risk first observed in people who worked in uranium mines, which spurred scientists to start testing radon levels inside houses and buildings.
"Some homes had radon levels close to some of the lower levels in the mines," Michael Bellamy, a medical physicist at Memorial Sloan Kettering Cancer Center in New York said last year in a story published by the health system.
Kevin Stewart, director of environmental health at the American Lung Association, described radon as being "very insidious" because people breathing it in do not exhibit immediate symptoms.
The only way to know if radon is present is to have a home's air quality tested – something the U.S. Surgeon General started urging Americans to do in a 2005 national health advisory. New houses can be just as vulnerable as older homes to radon, since the gas filters out of the ground.
People can test for radon in homes with kits sold at hardware stores or by hiring a certified testing company. If radon levels are above EPA standards, homeowners are advised to hire a certified mitigator to install a system that pulls the radon from beneath the house and vents it outside through a pipe.
Installing a radon mitigation system costs $800 to $1,200, according to the Pennsylvania Department of Environmental Protection. Installation usually takes less than a day and does not require major home renovations, the Centers for Disease Control and Prevention says.
The EPA offers a consumer's guide to radon reduction.
Pennsylvania residents can call the DEP's Radon Division at (717) 783-3594, or the Radon Hotline at (800) 237-2366, for help interpreting radon test results and deciding next steps. A list of contractors for radon testing and mitigation also is available by calling (800) 237-2366.