A new study by Johns Hopkins researchers links elevated levels of radioactive radon in Pennsylvania homes to the flurry of natural gas wells drilled across the state using the controversial technique known as hydraulic fracturing, or "fracking."
In a paper published online Thursday in Environmental Health Perspectives, researchers with Hopkins' Bloomberg School of Public Health reported that radon levels in Pennsylvania homes have been on the rise since 2004, with the greatest increases in counties with the most wells drilled.
Brian S. Schwartz, an environmental health science professor and study leader, called the findings worrisome.
"We found things that actually didn’t give us the reassurance that we thought it would when we started it," he said.
Pennsylvania already has relatively high levels of radon, a colorless, odorless gas. Produced by the decay of uranium, a radioactive mineral found in most soils, the gas seeps into homes and buildings and can reach dangerous levels in poorly ventilated areas.
Long-term exposure to radon gas can increase a person's chances of getting cancer. Indeed, federal health officials say radon is the second leading cause of lung cancer, after smoking.
Working with Pennsylvania’s Geisinger Health System, the researchers analyzed more than 860,000 indoor radon measurements collected by Pennsylvania's Department of Environment Protection from 1989 to 2013. They checked the gas readings against a variety of factors, including underlying rock layers, community wealth and weather.
The study found that buildings relying on well water had higher indoor radon readings than those on municipal water. They also discovered that summertime first-floor readings tended to be higher in homes relatively close to fracked gas wells, compared with those farther away.
Though there could be other explanations, Schwartz said, the findings appear to be linked to the more than 7,000 gas wells that have been fracked in the state in the past decade. The process involves pumping large quantities of water, sand and chemicals into the ground, then bringing some of it back up with the gas.
Marcellus shale is known to contain uranium, the researchers note, and the flowback water and drilling wastes can contain elevated levels of radium, which can produce radon. They also suggest radon could get into buildings via the natural gas piped in for heating and cooking.
Pennsylvania recently released its own study, finding that there is little potential for harm, either to drillling crews or the public from radiation exposure from fracking operations.
But Schwartz said the Pennsylvania study was based on sampling for radon around nearly three dozen wells. He contended that the Hopkins study provides a better overview of potential exposure because it reviewed hundreds of thousands of readings across the state.
The study comes as lawmakers in Annapolis appear set to impose a 2 1/2-year moratorium on fracking in western Maryland, which sits atop a deposit of potentially gas-rich Marcellus shale.
Amid debate about the safety of fracking and its impact on people's health and western Maryland's tourism industry, the Senate voted 45 to 2 earlier this week to continue a 3 1/2-year de facto moratorium as the state studied how to mitigate the risks. The legislation requires state regulations be adopted by Oct. 1, 2016, but no permit could be issued until a year later.
Parts of Maryland also have high radon levels. Thirty percent of homes in Garrett County have registered radon levels at or above the threshold at which the Environmental Protection Agency recommends residents take steps to prevent long-term exposure to the gas. The average reading in the county was 5.6 picocuries, above the 4 picocurie threshold, according to EPA data.
But Schwartz said home radon readings may be a misleading indicator of the risks from fracking, as the drilling and extraction process may bring much more radioactive gas to the surface than is currently detected.