Here’s a link to EPA’s web site on their expert review of hydraulic fracturing, which says that Congress requested they

conduct analyses to assess the potential risks to drinking water posed by hydraulic fracturing of formations including coalbeds and shale for extraction of natural gas. Hydraulic fracturing (or hydrofracking) generates vertical and horizontal fractures in underground geologic formations to facilitate extraction of gas (or oil) from the subsurface. …

The site includes some documents, and I’d like to see this charge broadened. Hopefully their experts will also look at other risks: air pollution, environmental degradation, and the like.