A coalition of seven Northeastern states is preparing to sue the U.S. Environmental Protection Agency for failing to regulate methane emissions from the oil and natural gas industry.

Although the EPA in 2009 found that methane (along with other greenhouse gases) endangers the public’s health and welfare by contributing to global warming, the agency has not required oil and natural gas producers to control their methane emissions.

Such emissions are equivalent to the climate-change pollution produced by 64 million cars a year, according to the states, which also include Connecticut, Delaware, Massachusetts, Maryland, New York, Rhode Island and Vermont.

“We are prepared to sue to force action on curbing climate change pollution from the oil and gas industry,” New York Attorney General Eric Schneiderman said in a press release. “While it is clear that methane from oil and natural gas development contributes substantially to climate change pollution, regulators have failed to require the industry to use available and cost-effective measures to control these emissions.”

In 2012, the EPA revised emission standards under the Clean Air Act for the oil and natural gas industry, but did not address methane.

“EPA must fully comply with its legal obligations under the Clean Air Act to regulate emissions that endanger public health and welfare by controlling this significant source of dangerous greenhouse gas pollution,” the states said in a December 11 letter to EPA Administrator Lisa Jackson, informing her of their intention to sue.

“Consequently, unless you promptly correct these failures, we intend to file suit in federal district court against you as EPA administrator and EPA.”

Section 111 of the Clean Air Act requires EPA to establish “standards of performance” for emissions of air pollutants from categories of new, modified and existing sources, and to update them every eight years.

EPA issued proposed revisions for the oil and gas industry in August 2011 but left out methane. Numerous groups protested, arguing that EPA was required by statute to determine if it was “appropriate” to add standards for previously unregulated pollutants like methane.

Still, when the final rule emerged in April, methane still wasn’t on the list. At the time, EPA said, “We intend to continue to evaluate the appropriateness of regulating methane with an eye toward taking additional steps if appropriate.”

The states complain that EPA can’t just leave methane in limbo. “A district court has jurisdiction to compel EPA to make a determination one way or another as to whether revision of the oil and gas [standard] is appropriate and to issue any revision it determines is appropriate,” the letter states.

Contact Jenna Greene at jgreene@alm.com.