By Valerie Volcovici
WASHINGTON, Dec 13 (Reuters) - Fracking for oil and natural gas can contaminate drinking water under "some circumstances," the Environmental Protection Agency said in a report released Tuesday, which changes a previous finding that the drilling process does not cause "widespread, systemic" effects.
The final report from the agency concludes more than five years of research and backs down from its previous determination that fracking is not a systemic threat to drinking water nationwide.
EPA science adviser Thomas Burke said there were significant gaps in data that limited the agency's ability to examine effects on drinking water both locally and nationally.
Despite not giving a definitive answer about the impact of fracking on drinking water, Burke said the report offered the most comprehensive record of scientific data on the relationship.
"EPA's assessment provides the scientific foundation for local decision makers, industry, and communities that are looking to protect public health and drinking water resources and make more informed decisions about hydraulic fracturing activities," he said.
The report comes just weeks before President-elect Donald Trump takes office and begins to roll back some of the Obama EPA's most significant clean air and water regulations, including rules to curb methane leaks from oil and gas drilling.
Trump has said he wants to usher in a new era for fossil fuels and remove restrictions on drilling and mining.
Environmental groups welcomed the changes to the final EPA report.
"With a new administration coming in, this underscores the need for action at the federal level," said Amy Mall, senior policy analyst at the Natural Resources Defense Council. "Now, more than ever, states and communities must use their power to guard against these very real risks."
Industry groups criticized the EPA for walking back its conclusion from its draft report that fracking does not have a systemic impact on water supplies.
"It is beyond absurd for the administration to reverse course on its way out the door," said American Petroleum Institute upstream director Erik Milito.
Oil group Energy in Depth spokeswoman Katie Brown said the overall conclusions remained largely the same.
"If fracking were a major threat to drinking water supplies, the data gathered by EPA would show it," she said. "But they don't." (Reporting by Valerie Volcovici; Editing by Lisa Von Ahn)