(Associated Press) A landmark federal study on hydraulic fracturing, or fracking, shows no evidence that chemicals from the natural gas drilling process moved up to contaminate drinking water aquifers at a western Pennsylvania drilling site, the Department of Energy told The Associated Press.

After a year of monitoring, the researchers found that the chemical-laced fluids used to free gas trapped deep below the surface stayed thousands of feet below the shallower areas that supply drinking water, geologist Richard Hammack said. Although the results are preliminary – the study is still ongoing – they are the first independent look at whether the potentially toxic chemicals pose a threat to people during normal drilling operations. But DOE researchers view the study as just one part of ongoing efforts to examine the impacts of a recent boom in oil and gas exploration, not a final answer about the risks.

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