The Environmental Protection Agency is asking nine natural gas companies to voluntarily disclose the chemical components used in a drilling technique called hydraulic fracturing.
The agency says the information is important as it conducts a study of the controversial drilling practice, also known as "fracking." Crews inject vast quantities of water, sand and chemicals underground to force open channels in sand and rock formations so oil and natural gas will flow.
The EPA is studying whether the practice affects drinking water and the public health. Letters were sent to nine leading national and regional hydraulic fracturing service providers, including Halliburton and Key Energy Services.
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