HARRISBURG — State environmental protection officials are studying the wastewater from Pennsylvania's fast-growing natural gas exploration activity to determine whether it is hazardous to human health.

Department of Environmental Protection spokesman Tom Rathbun said a chemical analysis the agency is doing should be finished this month.

Regardless of what is found, he said, the gas industry must come up with a way to treat the massive amounts of wastewater coming out of wells being drilled into the thick, black rock of the Marcellus Shale formation. The formation, more than a mile under Pennsylvania and several other states, could become the nation's largest natural gas field.

Exploration companies stress that the solution of chemicals, salts, metals and other components is not hazardous, but biologists and academics are not so sure.

"They don't have an analysis of what's in the wastewater they're pulling out," said Conrad Dan Volz, who directs the Center for Healthy Environments & Communities at the University of Pittsburgh. "What they're putting into the wells can chemically change and be added to underground, and no one is saying how much arsenic, manganese, cobalt, chromium and lead is in the stuff. Depending on the concentration, it could be a hazardous waste."

Drillers inject up to 54 substances into the water they use to break up the shale. Fracturing the rock gets more gas to flow, and some of the chemicals that are injected are intended to reduce friction when the water is pumped down into the well to blast the rock.

The DEP has issued more than 500 permits to drill on Marcellus Shale.