The Environmental Protection Agency issued guidance on February 11 on the use of diesel fluids in hydraulic fracturing. Fracking is largely outside of EPA's control, with much of the regulatory authority vested in the U.S. Department of Interior. However, EPA does have some control over the use of diesel, and its new guidelines are meant to clarify the definition of what constitutes "diesel."
Under the Energy Policy Act of 2005, EPA was "exempted" from regulating hydraulic fracturing under the Safe Drinking Water Act. This left EPA with very little authority over regulating fracking. The one area of control it still has is over the use of diesel. Drillers have to apply for permits with the EPA when they want to use diesel in their fracking operations.
It is unlikely that EPA's guidance will impact hydraulic fracturing operations significantly, as only about 2% of fracked wells involve the use of diesel. The oil and gas industry still pushed back against the move even though an official from the Independent Petroleum Association of America said that "diesel fuel use has already been effectively phased out of hydraulic fracturing operations" according to the L.A. Times. Instead of the guidance themselves being a burden, the industry fears that federal oversight will supersede state programs governing what is injected into the ground.