Nicholas School “Fracking” Study Among Top Five Most-Read Papers on PNAS Website

July 10, 2011

Tim Lucas, 919-613-8084,

DURHAM, N.C. – A recent study by Duke University researchers that found high levels of leaked methane in well water collected near shale-gas drilling and hydrofracking sites is one of the top five most-read papers on the Proceedings of the National Academy of Sciences website. 

The study was published in the PNAS Early Online edition in May and has generated widespread interest in scientific, industry and environmental circles, and more than 1,700 media stories worldwide.

It is the first peer-reviewed study to measure well-water contamination from shale-gas drilling and hydrofracking.

Authors Stephen Osborn, Robert B. Jackson, Avner Vengosh and Nathaniel Warner, all of Duke’s Nicholas School of the Environment, collected and analyzed water samples from 68 private groundwater wells across five counties in northeastern Pennsylvania and New York.

It found find measurable amounts of methane in 85 percent of the samples,. Those levels were 17 times higher on average in wells located within a kilometer of active hydrofracking sites. The contamination was observed primarily in Bradford and Susquehanna counties in Pennsylvania. Water wells farther from the gas wells contained lower levels of methane and had a different isotopic fingerprint.

The study found no evidence of contamination from chemical-laden fracking fluids, which are injected into gas wells to help break up shale deposits, or from “produced water,” wastewater that is extracted back out of the wells after the shale has been fractured.

Methane is flammable and poses a risk of explosion. In very high concentrations, it can cause asphyxiation.  Little research has been conducted on the health effects of drinking methane-contaminated water.  Methane isn’t regulated as a contaminant in public water systems under the EPA’s National Primary Drinking Water Regulations.

Hydraulic fracturing, also called hydrofracking or fracking, involves pumping water, sand and chemicals deep underground into horizontal gas wells at high pressure to crack open hydrocarbon-rich shale and extract natural gas.  Shale gas comprises about 15 percent of natural gas produced in the United States today. The Energy Information Administration estimates it will make up almost half of the nation’s production by 2035.

The Duke team collected samples from counties overlying the Marcellus shale formation. Accelerated gas drilling and hydrofracking in the region in recent years has fueled concerns about well-water contamination by methane, produced water and fracking fluids, which contain a proprietary mix of chemicals that companies often don’t disclose.

All funding for the study – which can be read online here– came from the Nicholas School and Duke’s Center on Global Change.

Independent of the PNAS study, the authors and colleagues at the Center on Global Change, Nicholas School and Nicholas Institute for Environmental Policy Solutions issued a white paper on hydrofracking at It includes recommendations for monitoring and addressing potential environmental and human health risks.