The Environmental Protection Agency has announced that it will study how hydraulic fracturing impacts water quality and public health, something that New York environmental groups and elected officials had pressed the EPA to do.

The state is developing an environmental document that would clear the way for Marcellus Shale drillers to use a combination of deep horizontal wells and high-volume hydrofracturing. But the energy companies' plans to hydrofrack in the shale have raised concerns about water contamination, particularly in New York City's upstate water supply, which is within the shale formation.

The EPA promises that it will conduct a peer-reviewed study. A news release sent out this morning doesn't specify much of what the study will look at, though. What should be paramount is fracking's effect on water resources - whether it's surface water or underground aquifers -and the news release leaves the impression that the EPA agrees.

The EPA should also focus on the makeup of fracturing fluids - the slurry of water, abrasives, and chemicals forced down the wells at high pressure. In most states, drillers keep the blends secret, claiming that the composition is proprietary information. That prevents residents from knowing what, exactly, the companies are blasting into the ground.