The natural gas drilling industry refuses to disclose what potentially harmful chemicals are used in thousands of hydraulic fracturing gas wells across the country, despite evidence that the chemicals are poisoning drinking water supplies. As concerns mount, several states are considering action to curb use of the process despite the federal government's efforts to encourage it with large subsidies and environmental exemptions.

During hydraulic fracturing, also known as "fracking," large amounts of sand and water are pumped at high pressure into a well. This causes small cracks and fissures to open deep in the layers of rock, releasing previously trapped molecules of natural gas. The mixture pumped deep into the ground usually contains a small proportion of chemicals included to reduce friction, prevent clogging of the fractures, and to prevent corrosion of machinery. These chemicals may end up in underground drinking water supplies, be spilled into surface waters, or evaporate as air pollution.

A recent investigation of hydraulic fracturing by ProPublica revealed documented cases of water contamination and other hazardous events resulting from the drilling process in several states. Drilling companies have consistently maintained that the procedure is safe, referring to a 2004 U.S. Environmental Protection Agency (EPA) study that found no risks to drinking water. However, ProPublica discovered several problems with EPA's conclusions, including statements within the report that fluids migrated unpredictably and to greater distances than previously thought, which were left out of the conclusions. Additionally, ProPublica noted that agency documents appear to indicate that EPA negotiated directly with the gas industry before finalizing its report conclusions.

Among the reports of damage to environmental and public health resulting from hydraulic fracturing are more than 1,000 cases of documented water contamination in Colorado, New Mexico, Alabama, Ohio, and Pennsylvania. In addition to contamination from the below-ground drilling, leaks and spills from trucks and waste pits are also causing problems. Tracking the contamination is especially difficult because drillers refuse to disclose the chemicals being used. Despite the secrecy, some information on the chemical mixture has been pieced together. Among the identified chemicals are volatile organic compounds (VOCs) such as benzene, toluene, ethyl benzene, and xylene.

According to a chemical analysis by the Environmental Working Group and The Endocrine Disruption Exchange (TEDX), a Colorado research organization, of the more than 300 suspected hydraulic fracturing chemicals used in Colorado, at least 65 are federally listed hazardous substances, and little is known about the rest. Despite the risks associated with the 65 hazardous chemicals, the drilling operations are exempt from environmental reporting requirements and use of the chemicals is not controlled. The drilling industries are exempt from numerous environmental regulations — and the accompanying reporting requirements and public scrutiny — authorized by such laws as the Clean Water Act, the Clean Air Act, the Resource Conservation and Recovery Act, the Comprehensive Environmental Response, Compensation, and Liability Act (Superfund), and the Safe Drinking Water Act (SDWA). Reps. Diana DeGette (D-CO), John Salazar (D-CO), and Maurice Hinchey (D-NY) introduced legislation, H.R. 7231, on Sept. 29 to remove the SDWA exemption originally created by the 2005 Energy Policy Act. The legislation is expected to be reintroduced in 2009.

The health risks from fracking chemicals was made clear in the summer of 2008 when a Colorado nurse almost died from exposure while treating a gas field worker whose clothing had been doused with the chemicals. Despite the nurse suffering from heart, lung, and liver failure, plus kidney damage and blurred vision, the drilling company refused to reveal to her doctors the "proprietary" chemicals used in hydraulic fracturing. While the nurse eventually recovered, she was never told to what she had been exposed.

For Colorado health officials, the chemical exemptions, regulatory loopholes, and missing data are a cause for concern. "We are just working in the dark," says Dr. Martha Rudolph, director of environmental programs for the Colorado Department of Public Health and Environment in a report for Newsweek. "We don't know the impact on the potential health on humans might be. We need to."

Claiming that the specific chemicals used in the drilling process are confidential business information and that disclosure would threaten their "competitive advantage" over competing firms, drilling companies have managed to operate wells nationwide without revealing what chemicals they are using. Halliburton, the oil and gas services firm and a pioneer of hydraulic fracturing, has threatened to pull its affected operations out of Colorado if it is forced by the state to disclose the chemicals it is using.

A major expansion of natural gas drilling is being planned for upstate New York within the region supplying New York City's water. However, New York City and state officials have asked the state Department of Environmental Conservation (DEC) to ban all gas drilling in the city's watershed, which overlaps the Marcellus Shale, a geologic region of high natural gas potential underneath New York, Pennsylvania, and West Virginia, until further studies on its impact can be done. The Marcellus Shale is estimated to contain enough natural gas to fuel the country's gas needs for fourteen years.

There has been a dramatic expansion of gas and oil drilling across the United States during the last eight years. The Bush administration has allowed more oil and gas drilling on western public lands than any administration in at least 25 years, and fracking is used in nine out of ten of these natural gas wells. Not only has the government allowed fracking to occur with lax oversight and regulatory exemptions, the government has also actively encouraged oil and gas companies with significant federal subsidies for exploration and drilling, including fracking. An analysis by Friends of the Earth released in July found that oil and gas companies would receive more than $32.9 billion in different subsidies over the next five years, including seven new provisions that were included in the Energy Policy Act of 2005 (PL 109-58). A report released by Taxpayers for Common Sense (TCS) on Nov. 14 details those seven new provisions, calculating they will cost taxpayers $2.3 billion through 2015.