Hydraulic fracturing, also known as fracking, is a process that injects fluid at high pressure deep underground to open and enlarge cracks in rock formations. This process stimulates the flow of natural gas, increasing the amount that can be extracted. Most fracking fluids are water based. A solid material, such as sand or ceramic beads, is added to the fracking fluid to keep the fractures open and permeable after the pressure is reduced. Other chemical additives are used, depending on the characteristics of the particular well. For example, some chemicals reduce friction to allow pumping at a higher rate than with water alone; others help dissolve minerals; and some prevent bacterial growth.

Many of the chemicals used in fracking fluids can also be found in foods, cosmetics, soaps, and household cleaners. However, that does not mean that they are safe; dosage is an important factor when evaluating hazardous materials. Although the total concentration of chemical additives in fracking fluid is generally less than 2 percent, millions of gallons of fluid are typically used to drill a well. That means that thousands of gallons of chemicals could be used that might potentially impact human health and the environment.

In 2005, the Energy Policy Act exempted hydraulic fractured wells from regulation under the Safe Drinking Water Act. Some states may require disclosure of ingredients to state environmental agencies or health officials, but fracking fluids are largely unregulated. Mining companies each have their own proprietary formula. Some chemicals used in the fluids are known, but the exact compositions are kept confidential because they are claimed to be trade secrets. (The formula of a particular fluid may provide an advantage over other companies.) However, concerns over possible contamination of water resources from fracking fluids has led to controversy over whether the industry should be allowed to keep the formulas confidential.

Currently it is difficult to assess the connection between health problems and the fracking process because so little is known about the composition of the fluids. Even if a company discloses the chemicals it uses, the exact concentrations of chemicals may not be known. The Environmental Protection Agency has asked a number of fracking service providers to provide detailed information about their fluids as part of a study on the effects of fracking on drinking water and public health; research is due to be finished in 2012. Until more is known about the effects of the hazardous chemicals contained in fracking fluids, some people might argue that the industry should follow the precautionary principle—that it is their responsibility to protect the public from harm—and use safer chemicals in their fluids. Some companies are already making more environmentally friendly fracking fluids available.

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