To force natural gas out of the shale deposits, drilling companies pump a mixture of chemicals miles underground. As Popular Science writes:
Typically fracking chemicals are injected 3,000 to 9,200 feet (900 to 2,800 meters) underground, where it has been generally thought that they couldn't make it to the surface or mix with reservoirs of drinking water. But that isn't true, as scientists have found geological connections between these deep injection sites and surface drinking water, at least in the Appalachian Basin.
Of the roughly 190 different compounds used at various fracking wells, about one-third lack sufficient toxicity information, according to a study presented at the American Chemical Society on Wednesday. Of the known chemicals, most are rendered harmless with appropriate treatment. Most - but not all. "There are a number of chemicals, like corrosion inhibitors and biocides in particular, that are being used in reasonably high concentrations that potentially could have adverse effects," says William Stringfellow, an environmental engineer at the University of the Pacific, in a press release.
There's no question that the fluids used in the fracking process have been responsible for ecological damage. When an oil and gas company illegally discharged an acidic mixture near a Kentucky stream in 2009, the fluids "killed virtually all aquatic wildlife in a significant portion of the fork," reports the Fish and Wildlife Service. Similarly, seventeen cows died within an hour of a worker accidentally leaking fracking chemicals into a farm pasture.
Again, ambiguity compounds this problem - it's not clear which wells have used which chemicals. "Some of the wells in the chemical disclosure registry were fractured with fluid containing 20 or more undisclosed chemicals," states Kimberly Terrell, a Smithsonian Conservation Biology Institute researcher and one of Souther's co-authors. "This is an arbitrary and inconsistent standard of chemical disclosure."
Neither Souther nor her colleagues are "anti-shale development," she tells InsideClimateNews. "We're anti-lack of knowledge." Fracking wells aren't likely to disappear soon. But there's too much at stake - particularly for sensitive species like pronghorn antelope and hellbender salamanders, Souther points out - to allow fracking's environmental impacts to stay in the dark.