TEMPO.CO, Jakarta - Fracking doesn’t appear to be allowing methane to seriously contaminate drinking water in Pennsylvania, a new study finds—contrary to some earlier, much publicized research that suggested a stronger link. But the lead authors of the two bodies of research are sparring over the validity of the new results.

The new study of 11,309 drinking water wells in northeastern Pennsylvania concludes that background levels of methane in the water are unrelated to the location of hundreds of oil and gas wells that tap hydraulically fractured, or fracked, rock formations. The finding suggests that fracking operations are not significantly contributing to the leakage of methane from deep rock formations, where oil and gas are extracted, up to the shallower aquifers where well water is drawn.

The result also calls into question prominent studies in 2011 and 2013 that did find a correlation in a nearby part of Pennsylvania. There, wells closer to fracking sites had higher levels of methane. Those studies, however, were based on just 60 and 141 domestic well samples, respectively.

“I would argue that [more than] 10,000 data points really tell a better story,” says hydrogeologist Donald Siegel of Syracuse University in New York, whose team published the new study online this month in Environmental Science & Technology. Chesapeake Energy Corp., which has large oil and gas stakes in Pennsylvania, supplied the researchers with the database, the largest of its kind, and also funded the work.

Fracking relies on the high-pressure injection of water, sand, and other chemicals to create microfractures in rock formations, thereby making it easier to draw out oil and gas. The term is also used more generally to describe a host of unconventional extraction techniques, such as horizontal drilling, which have helped make the United States the top producer of crude oil in the world. The Marcellus Shale formation, an organic-rich mudstone running from West Virginia to New York, was one of the first to be exploited by fracking. But the process has been dogged by concerns over its environmental impact and also its impacts on the climate, because any leaking methane acts as a powerful greenhouse gas.

ENN