Pennsylvania joined 14 other states Tuesday in a federal suit challenging the Environmental Protection Agency's decision to delay for a year new ozone pollution rules, with Gov. Wolf saying the wait could hurt children who suffer from asthma.

Wolf and state Attorney General Josh Shapiro announced the suit during a news conference along the banks of the Schuylkill at 24th and Walnut Streets in Philadelphia.  The suit was filed in federal appeals court in Washington.

Wolf said the lower ozone levels would reduce health-care costs.  He said past EPA findings showed 230,000 asthma attacks a year could be prevented in American children if pollution were reduced.

"What is gravely concerning is that children who suffer from asthma and respiratory illnesses are particularly vulnerable to elevated ozone levels," Wolf said. "The ozone standard that the EPA is delaying would have serious positive health benefits for our children."

At issue for the states involved in the suit is a 2015 Obama-era EPA rule that lowered allowable ground-level ozone levels from 75 parts per billion to 70 parts per billion under National Ambient Air Quality Standards.  Governors had to submit a list of areas that were not in compliance, and then the EPA had up to two years to declare which areas did not meet standards, and could seek an extension if it needed more information.

Scott Pruitt, the EPA administrator, invoked that extension in June, saying the EPA needed "time to better understand some lingering, complicated issues so that air attainment decisions can be based on the latest and greatest information."  He also established an Ozone Cooperative Compliance Task Force "to develop additional flexibilities for states to comply with the ozone standard."

An EPA spokesman said the agency does not comment on pending litigation.

Wolf and Shapiro say they believe that the EPA has all the information it needs and that the delay is being driven by the ideology of the Trump administration, which has said it intends to address "job-killing" environmental regulation.

"Pennsylvanians suffer and I believe their constitutional rights are being threatened," said Shapiro, who disagrees that the regulations will harm businesses. He continued that the suit, if successful will, "force the EPA to do its job and protect Pennsylvanians, and protect Americans without any further delay."

Ground-level ozone, or smog, is a result of pollution.  Nitrogen oxides and volatile organic compounds combine under sunlight and heat to help produce ozone.  Philadelphia has long had difficulty with smog because it is surrounded by emissions given off by motor vehicles, industry, power plants, and refineries.  Pennsylvania named the Philadelphia and Pittsburgh metropolitan areas in its report to the EPA in 2016 as exceeding ozone limits.

In May, environmental groups sued the EPA over failing to make a final determination on whether Philadelphia meets acceptable levels of ozone.  And, in April, an advocacy group, using EPA data, issued a study saying Philadelphia was among the smoggiest Northeastern cities.