An April report from the U.S. House of Representatives said oil and gas companies involved in shale gas production used fluids containing chemicals that are carcinogenic, considered harmful in drinking water or are listed as hazardous under the Clean Air Act.
Colorado Gov. John Hickenlooper, a Democrat, told an audience at the Colorado Oil and Gas Association Energy Epicenter in Denver that groundwater sampling before and after hydraulic fracturing, or fracking, of shale gas deposits was needed to allay public "paranoia," the Platts news agency quoted him as saying.
He dismissed a recent damning report on fracking in The New York Times as a baseless article meant to excite the public with "hyperbole."
Some state environmental agencies and energy companies say that, if done correctly, fracking poses little threat to the environment.
The U.S. Energy Information Agency said shale gas production will make up about half of the total natural gas production in the United States in the next 25 years.