RENEE MONTAGNE, HOST:
Let's turn to the ongoing controversy about fracking, the technique that injects water deep into the earth to extract natural gas and has generated fears that it could lead to contamination of drinking water in wells nearby. A new scientific study eases some of that worry, at least a bit. NPR's Dan Charles has more.
DAN CHARLES, BYLINE: There have been cases in which contamination has turned up in drinking water in places where fracking is common. And it's raised fears that when gas companies drill their fracking wells, it allows oil and gas that's been trapped a mile underground to migrate up toward the surface and leak into aquifers that people rely on for their drinking water. So Desiree Plata, who teaches chemical and environmental engineering at Yale University, sampled drinking water from 64 wells in northeastern Pennsylvania. There's a lot of fracking going on in that area.
DESIREE PLATA: Towards the end of our study, it was difficult to find a home that was more than a few kilometers from a natural gas well production pad.
CHARLES: She and a colleague looked for contamination in the water. And they found some, but only in a handful of wells.
PLATA: And really, even using that word contamination is a stretch because when these detections were made, they were still at very low concentrations.
CHARLES: None of the samples violated drinking water standards. The scientists also tried to figure out where the contaminants came from. And there were clues - chemical fingerprints - that convinced them these chemicals were spilled on the ground near fracking sites and then seeped down into drinking water. They did not come up from deep underground. Plata says that's good news.
PLATA: Failures at the surface are easier to control than failures beneath the surface of the earth.
CHARLES: And you know about them, I guess.
PLATA: You know about them, right. If you know there's a spill, you can respond to it.
CHARLES: The report appears this week in the proceedings of the National Academy of Sciences. Dan Charles, NPR News. Transcript provided by NPR, Copyright NPR.