The U.S. Environmental Protection Agency for the first time has linked the natural gas drilling practice of hydraulic fracturing, known as fracking, to polluting water supplies. On Thursday, the EPA said it had found fracking chemical compounds in the groundwater beneath a remote Wyoming community where residents have complained of contamination. The EPA has advised the residents not to drink the water. The finding could have major implications for areas around the country where gas companies are seeking state approval for massive fracking projects in shale formations.