Those who get drinking water from wells close to gas drilling sites are in much greater danger of having their water is contaminated by methane gas, according to a study published in The Proceedings of the National Academy of Sciences believed to be the first to establish a link between gas drilling and methane contamination.
The study's authors examined 60 water wells in Pennsylvania and upstate New York, and found those close to gas drilling sites contained on average 17 times more methane.
Methane is not poisonous, but it is highly combustible and can cause asphyxiation. There have been several recent documented cases of explosions resulting from methane buildup in drinking water tanks. Methane is also the main component of natural gas.
Robert Jackson, a biology professor at Duke and a co-author of the study, said water wells can fill with methane that comes from thousands of feet underground if natural gas is being tapped in the immediate vicinity.
"The simplest explanation for what we observed is probably leaky well casings," Jackson said. "That can happen with traditional gas wells and it can certainly happen with fracked gas wells."
Jackson added that the high pressure used in hydraulic fracturing, or fracking, may pose an additional risk, but said the question needs more study.
While seeming to confirm one concern related to fracking, the study did not find evidence that the chemicals used in fracking have seeped into water wells. These chemicals, which are exempt from federal reporting requirements, are rumored to include carcinogens and other serious health hazards.
"There are many things in the fracking fluids that we couldn't look for," Jackson said. "We don't know what they are. We don't have the analytical capabilities in our labs here at Duke to analyze everything."
In a related white paper, the authors of the study call for disclosure of fracking chemicals and other measures.
Jackson said regulators should take a robust approach to the recent boom fracking and directional drilling, the tools used to get gas out of challenging shale formations. But it is possible to drill for natural gas relatively safely, and gas is more attractive than the alternatives.
"Are the problems associated with shale gas extraction worse than the consequences of mountaintop mining for coal? I don't think so," he said.