"These findings worry us." That from the head of a new study out of Johns Hopkins Bloomberg School of Public Health suggests fracking could bring radon to the surface—raising levels of the odorless toxic gas in our homes. The researchers looked specifically at 860,000 readings taken in Pennsylvania homes, using a state database that covers 1987 to 2013. What they found per their study, published in Environmental Health Perspectives: "Basement radon concentrations fluctuated" during that period, "but began an upward trend from 2004-2012 in all county categories, higher levels in counties with ≥100 drilled wells vs. counties with none." That roughly coincides with when fracking began in the state: Between 2005 and 2013, 7,469 unconventional wells that use fracking to extract natural gas from shale were drilled there.
A press release notes that homes and buildings in the rural and suburban areas where most unconventional natural gas wells are located had a 39% higher concentration of radon than their urban counterparts. The study doesn't pinpoint how the excess radiation got in; study author Joan A. Casey suggests one of three ways: via well water that's been affected by fracking, from air around the wells, or through the natural gas produced by these wells and used in homes. Still, USA Today notes that the study doesn't "conclusively prove" that fracking lets radon loose in the first place. As for why Pennsylvania, the authors studied it in part because it has one of America's highest residential radon levels; the state sits on bedrock that contains radium, which degrades into radon, the second-leading cause of lung cancer worldwide.