Twoenvironmental groups have joined forces in a citizen lawsuit against the U.S.EPA in an effort to force the agency to review National Ambient Air QualityStandards for nitrogen and sulfur pollution.

InApril, the Center for Biological Diversity submitted a letter of intent threatening to bring thenew lawsuit, but the group had to wait 60 days before officially filing.

TheCenter for Environmental Health joined in the complaint, which was filed July 7with the U.S. District Court for the Northern District of California. Thegroups alleged that the EPA and Administrator Gina McCarthy failed to completethorough reviews of the NAAQS for sulfur and nitrogen and the science behindthose standards, as required under the Clean Air Act. The EPA regulates sulfurdioxide, or SO2, and nitrogen dioxide, or NO2, under the NAAQS program. Thecurrent NO2 and SO2 standards were issued in 2010, and although the agency lastreviewed them in 2012 it ultimately decided not to change them at that time.

TheClean Air Act requires the EPA to conduct a review of NAAQS standards everyfive years and revise as necessary. The agency must publish the results of thatreview in the Federal Register. The groups alleged that the EPA failed to meetthose deadlines, and therefore asked the court to declare the agency inviolation of the Clean Air Act and issue a mandatory injunction requiring it totake action.

"There'sno reason to delay stronger protections for millions of Americans sufferingfrom dirty air linked to coal and gas pollution," said Jonathan Evans,environmental health legal director at the Center for Biological Diversity. "TheClean Air Act saves lives and cleans up our skies, but it only works when thereare strict protections in place to hold polluters accountable and protect themost vulnerable people in our communities."