Advancements in technology over the past few decades, combined with rising oil and electricity prices, have led to a large increase in drilling horizontal wells for natural gas and oil. Fracking - the blasting of water, sand, and chemicals into shale rock to create fissures and release oil and gas - is taking place in 31 U.S. states.
There were more than 493,000 active "natural" gas wells in the U.S. in 2009, which is almost double the number in 1990. Around 90 percent of these have used fracking.
The Marcellus Shale is a mass of shale deposits in New York, Pennsylvania, Ohio, West Virginia, and neighboring states. As one of the largest "natural" gas fields in North America, it is one of the top targets of the gas industry. Energy companies have honed in on the region, as well as in other major shale deposits throughout the country, including the Haynesville Shale, Fayetteville Shale, Eagle Ford Shale and Barnett Shale.
In December 2011, the U.S. Environmental Protection Agency linked fracking to groundwater contamination for the first time in Wyoming. The agency is currently undergoing a multiyear national study of the effects the process has on water supplies.
Fracking is not regulated by federal statutes governing water safety, because industry lobbyists obtained an exemption from this law, known as the "Halliburton loophole." Although no complete list of the chemicals used by each drilling company exists, information obtained from environmental clean-up sites demonstrates toxic substances.
An April 2011 report filed with the U.S. House of Representatives, showed that 29 chemicals used in some 650 different fracking products are carcinogens, subject to regulation under the Safe Drinking Water Act for their risks to human health.
A 2011 investigation by the New York Times, based on thousands of internal EPA documents, "reveal that the wastewater, which is sometimes hauled to sewage plants not designed to treat it and then discharged into rivers that supply drinking water, contains radioactivity at levels higher than previously known, and far higher than the level that federal regulators say is safe for these treatment plants to handle. ...Other documents and interviews show that many E.P.A. scientists are alarmed, warning that the drilling waste is a threat to drinking water in Pennsylvania. Their concern is based partly on a 2009 study, never made public, written by an E.P.A. consultant who concluded that some sewage treatment plants were incapable of removing certain drilling waste contaminants and were probably violating the law."
In a March 2012 Rolling Stone piece, journalists Jeff Goodell writes: "An even larger threat is the flowback waste that is pumped out after a well is fracked. It's a salty brine, mildly radioactive, and laced not just with toxic chemicals but with natural hydrocarbons and heavy metals like barium and benzene, which are known carcinogens even in minute quantities."
According to a 2009 article published in ProPublica, three company spokespeople and a regulatory official said that as much as 85% of the fluids used during hydraulic fracturing is regularly left after wells are drilled in the Marcellus Shale. According to the article, this means that "for each modern gas well drilled in the Marcellus and places like it, more than 3 million gallons of chemically tainted wastewater could be left in the ground forever. Drilling companies say that chemicals make up less than 1 percent of that fluid. But by volume, those chemicals alone still amount to 34,000 gallons in a typical well."
The impact of fracking on wildlife has been documented in a 900 page Environmental Impact Statement filed by the New York Department of Environmental Conservation in September 2011.
Environmental reporter and activist Iris Marie Bloom has been interviewing residents in Pennsylvania to document how fracking has impacted them. In February 2012, she reported on the experience of Janet McIntyre, who lives in an area where she is surrounded by 30 gas wells: "Janet described her own water as foaming out of the tap on two occasions, which she refers to as 'attacks' because it felt their water was under attack by the gas drilling company. She said it was purple. Other residents have reported their water turning orange, red, and brown."