Fourteen American states and a collection of lobby groups have filed suit against the US Environmental Protection Agency (EPA), accusing it of endangering public health with weak air quality standards.

The plaintiffs have accused the agency of inadequate standards for governing pollutant levels in the US after EPA administrator Stephen Johnson announced a decision on ground-level ozone safety levels in March.

“The administrator set a standard that was significantly less protective than his own science advisors had unanimously recommended,” said Vickie Patton, a spokesperson for litigant the Environmental Defense Fund, which has launched a parallel suit to the states’ action along with organisations including the American Lung Association.

Under the decision, a secondary standard for ground-level ozone - a major component of the smog that affects many US cities - was not reduced, in spite of scientific advice to the contrary. According to Congressional testimony, the White House intervened and influenced the EPA’s decision.

The states will ask the courts to force the EPA to adopt ozone standards in line with the original scientific advice.

States suing the EPA include Connecticut, Delaware, Illinois, and California (which is also suing the EPA over its refusal to let the state impose stricter automobile-based emissions standards than federal standards allow). Massachusetts, which originally won the legal right to force the EPA to regulate CO2 emissions under the Clean Air Act last year, is also suing. The City of New York and the District of Columbia are also signatories to the suit.

One month after Johnson’s decision, the National Research Council issued a report stating that short-term exposure to current levels of ozone in many parts of the US could lead to premature death. The report considered whether there is a threshold of exposure below which there is no risk of death. “If a threshold exists, it is probably at a concentration below the current public health standard,” the National Academies said.