WASHINGTON (Reuters) - The state of Delaware on Tuesday said it would sue the U.S. Environmental Protection Agency for failing to ensure that nearby Pennsylvania and West Virginia curbed upwind air pollution from their power plants.

“The Clean Air Act entitles Delaware to relief from upwind pollution and the remedy we are seeking is reasonable and within EPA’s authority and responsibility to grant,” said Delaware Governor John Carney.

Delaware says more than 90 percent of ground-level ozone, or smog, in Delaware originates from emissions in upwind states. Despite previously petitioning the EPA four times in 2016 to crack down on the upwind pollution, the governor said the state has not gotten relief.

“We are simply asking that the EPA require these power plants that pollute Delaware’s air to run their existing pollution control equipment when the plants are in operation,” the governor said.

Delaware’s Department of Natural Resources and Environmental Control said that although the state has made strides in improving its air quality, out-of-state emissions keep it from meeting federal air quality standards.

“It is now time for EPA to hold upwind sources accountable for ozone emissions that are impacting downwind states,” the department’s secretary, Shawn Garvin, said.