BALTIMORE, April 9 (UPI) -- The odorless radioactive gas known as radon is on the rise in Pennsylvania, and researchers suggest fracking is to blame. Since 2004, the year hydraulic fracturing activity kicked into high gear, radon readings in homes have been spiking.
A new study, conducted by researchers at the Johns Hopkins Bloomberg School of Public Health, found that 42 percent of radon readings in the state registered above what the federal government defines as safe. Radon is the second leading cause of lung cancer after smoking.
The researchers also found that radon readings are higher on average in counties with considerable fracking activity when compared to places where little to no fracking occurs. There were no significant county discrepancies prior to 2004, the study points out.
"One plausible explanation for elevated radon levels in people's homes is the development of thousands of unconventional natural gas wells in Pennsylvania over the past 10 years," researcher Brian S. Schwartz, a professor of environmental health sciences at the Bloomberg School, said in a press release. "These findings worry us."
The researchers drew the connection between radon and fracking after analyzing trends in more than two decades of radon levels -- including 860,000 indoor radon readings from 1989 to 2013. Levels are recorded by the Pennsylvania Department of Environment Protection when homes are bought and sold. Researchers say their analysis controls for mitigating factors and ulterior explanations for heightened radon concentrations -- whether they be geology, water source, season, weather or community type.
While the exact mechanism causing radon's increasing presence isn't clear, the common denominator seems to be fracking. Researchers say it's possible radon is escaping via the wastewater pumped at high pressure deep into underground shale rock to release natural gas. It's also possible, scientists say, that it's seeping into the air through holes in the gas wells. Shale-derived gas may also simply contain more radon than other types.
"By drilling 7,000 holes in the ground, the fracking industry may have changed the geology and created new pathways for radon to rise to the surface," said lead study author Joan A. Casey, a Bloomberg grad and now a researcher at the University of California, Berkeley. "Now there are a lot of potential ways that fracking may be distributing and spreading radon."
Environment officials in Pennsylvania recently conducted an air sample study near gas wells and found no evidence of higher concentrations of radioactive gas. But researchers say measuring levels in homes of a broader range is a more accurate way to measure and understand trends. Their findings, they say, suggests officials should revisit the issue.
The study was published this week in the journal Environmental Health Perspectives.