The Halliburton loophole, which exempts fracking from regulation under the Safe Drinking Water Act, was justified by an EPA study about fracking completed under the George W. Bush administration. The study concluded that fracking posed no risk to drinking water.
However, a working draft of the study prepared by a government contractor suggested that fracking could pose risks to drinking water. The EPA changed parts of that draft.
In drafts of the executive summary, for example, typically a report's most widely read section, the authors referred to potential threats to public health as the reason for the study. "The goal of this Phase I study was to determine if a threat to public health exists as a result of USDW [Underground Sources of Drinking Water] contamination from hydraulic fracturing fluid injection into CBM [coalbed methane] wells, and if it does, whether the threat is great enough to warrant further study," the authors wrote.
The final version of the report omits mention of public health except in the discussion of methodology and in paraphrasing public comments deep into the 463-page study.