"We did not find evidence that these mechanisms [of potentially affecting water] have led to widespread, systemic impacts on drinking water resources in the United States," the report said.
Hydraulic fracturing, or fracking, is a process that involves pumping water, sand and chemicals into a well to extract oil or gas. Environmentalists say fracking poses health risks, often citing the affects on drinking water reserves.
In its report, the EPA notes that its findings could have been limited because of an insufficient amount of data and the presence of other possible contaminates that made it impossible to conclude fracking's effects on certain areas.
"The study was undertaken over several years and we worked very closely with industry throughout the process," Tom Burke, EPA's science advisor and deputy assistant administrator of EPA's Office of Research and Development, said on a conference call hosted by the agency.
He added that the limitations in data were not a function of companies' cooperation, but were—in many instances—a question of scientific capabilities.
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Still, members of the energy industry were already celebrating the report.
"With this new report, it couldn't be clearer that shale development is occurring in conjunction with environmental protection and the claims by anti-fracking activists have been thoroughly debunked," a post from the Independent Petroleum Association of America's outreach campaign said.
In fact, the assessment includes several examples of fracking activities contaminating drinking waters, Burke said, adding that the report is not meant to issue a final conclusion on the process's safety.
"This is a study of how we can best protect our water resources. It's not a question of safe or unsafe," he said.
The EPA report was the result of Congress urging the group to conduct an assessment, and includes meta-analysis of prior studies and original agency research, Burke explained.
He emphasized that the draft assessment is not meant to directly inform policy, but is simply an advance in scientific understanding that can serve as a "foundation for future decisions."