Several Democratic senators said Tuesday that the Environmental Protection Agency should step up regulation of the natural gas industry because they are concerned that toxic chemicals used in drilling could enter the public water supply.
In a Senate hearing, Democrats pressed the agency about the consequences of a fast-growing drilling technique called hydraulic fracturing, or hydrofracking, that involves pumping chemicals and water deep underground to release gas deposits.
“The industry has failed to meet minimal acceptable performance levels for protecting human health and the environment,” said Senator Benjamin L. Cardin, Democrat of Maryland and chairman of the Water and Wildlife Subcommittee of the environment committee. “The question is, What is E.P.A. doing about this?”
A recent article by The New York Times reported that these drilling fluids, which are often processed at sewage treatment plants, contain radioactivity at levels far higher than federal regulators say is safe for these plants to handle.
Robert Perciasepe, the environmental agency’s deputy administrator, testified that state and federal regulators were collaborating to ensure that no contaminants from fracking entered drinking water.
Mr. Perciasepe said that the E.P.A. had commissioned an independent study of hydrofracking and that drilling companies had been asked for new details about the chemicals in the water delivered to treatment plants.
“Our primary role here is oversight on the state programs,” he said, “but they are running the programs. Where we see some imminent endangerment, we may take our own action.”
Republicans at the hearing expressed concern about increasing the E.P.A.’s regulatory responsibilities. Current state regulations are adequate, said Senator James M. Inhofe of Oklahoma, adding that there are no cases of contaminated drinking water being linked directly to hydrofracking.
“These people have been doing a good job,” Mr. Inhofe said. “But the mentality in Washington is, nothing is done right unless it’s done in Washington.”
State regulators and environmental advocates from Colorado, Maryland, Oklahoma and Pennsylvania also testified that they were protecting the environment and ensuring the safety of drilling.
But Mr. Perciasepe said Pennsylvania could use more federal oversight. The state has granted permits to wastewater treatment plants that do not require adequate screening of the full range of contaminants that can exist in the drilling wastewater, he said.
The fate of the water — whether it is recycled, pumped back into the earth or sent to a treatment facility — has become a contentious environmental issue.
States have placed varying requirements on drilling companies. Some, like Wyoming, require that chemicals used in fracking be disclosed publicly. But others do not, a gap in information that Democrats said the E.P.A. should close.
“Water doesn’t recognize state boundaries,” said Senator Frank R. Lautenberg, Democrat of New Jersey. “You may live in a state that has strong laws against fracking, but if the state next door doesn’t, your family could still be at risk.”
The record in Pennsylvania, where natural gas drilling has grown sharply, shows why more oversight is needed, Mr. Cardin said. He noted that an E.P.A. letter to state officials warned that fracking wastewater “may present a threat to human health and the aquatic environment,” including to drinking water.
Natural gas companies in the Marcellus Shale reserve, under part of the Northeastern United States, have a much higher rate of violating environmental laws than do traditional gas companies, said Conrad Daniel Volz, director of the Center for Healthy Environments and Communities. Dangerous chemicals including barium, benzene and strontium have been found at unusually high rates in nearby water supplies, Mr. Volz said.