Cancer-causing radon has been found in some Pennsylvania water wells, adding slightly to the much bigger threat faced by homeowners from airborne sources of the radioactive gas.
Radon primarily enters a home through rock and soil surrounding the foundation. But a federal government study released Thursday found high levels of radon in 14 percent of Pennsylvania water wells tested between 1986 and 2015. Radon can be released from water and become airborne when someone washes the dishes, takes a shower or does laundry — slightly increasing the overall level in the home.
Radon, the second-leading cause of lung cancer after smoking, is a serious problem in Pennsylvania. About 40 percent of households statewide have indoor radon levels high enough to warrant taking action to vent the harmful gas, which can't be smelled or seen.
The U.S. Geological Survey examined more than 1,000 well samples and found a particularly acute threat from both groundwater and indoor air in York, Lancaster and Chester counties, according to its report.
The state Department of Environmental Protection says residents should test their air first, then, if they find an elevated level, test the well water. Radon can be removed from water with systems that use charcoal or aeration.
"Aside from getting tested, you're really not going to know what's going on," said Eliza Gross, a U.S. Geological Survey scientist who led the study.
About 21,000 lung cancer deaths per year are attributed to radon. The National Research Council has estimated that only a tiny fraction are due to radon in water. About 160 people could get lung cancer from breathing radon that escaped from water and another 20 could get stomach cancer from drinking radon-laced water, according to the estimate , which was released in 1998 but is considered authoritative.