Fifteen states on Tuesday sued Environmental Protection Agency Administrator Scott Pruitt for delaying the Obama administration's strict new rules for cutting smog-producing ozone emissions.

"By illegally blocking these vital clean air protections, Administrator Pruitt is endangering the health and safety of millions," said Democratic New York Attorney General Eric Schneiderman, who was one of the 15 attorneys general to file the lawsuit with the D.C. Circuit Court of Appeals.

He said the one-year delay of the regulations is another example of the "Trump EPA ... [choosing] to put polluters before the health of the American people."

Pruitt delayed the regulations in June while the EPA reviewed the regulations for possible changes and repeal.

Schneiderman led the charge to oppose Pruitt when he was Oklahoma attorney general and challenging the Obama administration's climate regulations. The New York attorney general also has led a high-profile investigation into news reports that Exxon Mobil suppressed its own scientific research from the 1970s that showed climate change would harm its business.

New York was joined by Democratic attorneys general from California, Connecticut, Delaware, Maine, Massachusetts, Minnesota, New Mexico, Oregon, Rhode Island, Vermont, Washington state, Illinois, Iowa, Pennsylvania, and the District of Columbia.

Josh Shapiro, the attorney general of Pennsylvania, a big fracking state, said in a statement that Pruitt is "choosing to ignore" a detailed study that his state environmental agency sent to the EPA identifying a number of regions in the Keystone State, including Philadelphia, "where smog is a serious health risk." He said the delay "is unacceptable."

The smog rules would cut ozone from 75 to 70 parts per billion, which critics of the rules, including manufacturers and the fossil fuel industry, say are nearly impossible to meet. They argue that most states had not met the previous air quality standards before the new rules were proposed and then finalized by the Obama administration.

Environmental groups think the EPA standards should be reduced to 65 parts per billion, which the agency had considered.

A decision the D.C. Circuit made last month on a separate EPA regulation for methane emissions may be telling in how it will rule on the smog suit.

The court had ruled that the EPA could not delay the methane rules on the oil industry for three years as it proposed to do. On Monday evening, the court issued an order directing Pruitt to enforce the methane rules after environmental groups filed a brief petitioning the court to do so.