In other environmental news, new evidence has emerged linking natural gas drilling to drinking water contamination. ProPublica reports federal officials in Wyoming have found that at least three water wells contain chemicals used in the natural gas drilling process of hydraulic fracturing. The Wyoming study marks the first time the EPA has undertaken its own water analysis in response to complaints of contamination in drilling areas. Residents in Pavillion Wyoming have complained for years that their water wells turned sour and reeked of fuel vapors shortly after drilling took place nearby. ProPublica reports precise details about the nature and cause of the contamination have been difficult for scientists to collect, in part because the identity of the chemicals used by the gas industry for drilling and fracturing are protected as trade secrets.