A pair of court decisions may force the U.S. Environmental Protection Agency to revise the way it handles the amount of air pollution allowed to travel from heavy polluting states, like Indiana, to downwind states.

The decisions came mid-September after two environmental groups and several states sued the EPA for not doing enough to protect states downwind of heavy polluters.

“The problem is that air pollution doesn’t stay within state boundaries,” Neil Gormley, staff attorney for environmental advocacy group Earthjustice told the Indiana Environmental Reporter. “And that’s exactly the problem that we have today. Many states, including a lot of states in the Midwest, have a lot of coal-fired power plants and other industrial sources of pollution that emit smog that blows across state lines and causes unhealthy air quality in downwind states.”

Gormley represented the two environmental groups, the Sierra Club and the Appalachian Mountain Club, in the suit.

The Clean Air Act outlines the EPA’s responsibilities for protecting and improving the nation’s air quality. Under the law, the EPA must establish emissions standards, known as National Ambient Air Quality Standards, for harmful air pollutants known as “criteria pollutants.”

A part of the Clean Air Act requires states to do something about the cross-state pollution. Under the “good neighbor” provision of the law, the EPA must prohibit states from emitting pollution in amounts that could affect air quality in other states and prevent them from attaining and maintaining pollutant standards.

The cross-state pollution requirements have been modified several times by new rules, with the most recent regulation issued in 2016 by the Obama administration.

The 2016 Cross-State Air Pollution Rule Update placed further limitations on emissions from power plants across state lines.

But the Sierra Club, Appalachian Mountain Club and several states sued the EPA in 2018, saying the rule did not go far enough to stop upwind states from spreading their pollution to downwind states.

“(The update) achieved some reductions in air pollution, which was good, but EPA admitted that the reductions that it achieved were not enough to achieve healthy air in downwind states,” said Gormley. “So, that was why we filed a lawsuit, and we argued that while a half step was better than nothing, EPA needed to finish the job. It needed to find a way to reduce the pollution enough that people living downwind will actually have the clean air that the Clean Air Act is intended to provide.”

The U.S. Court of Appeals for the District of Columbia Circuit on Sept. 13 found that the updated rule’s limited scope led to a significant omission — a deadline for compliance.

“The Update Rule does not require upwind states to eliminate their significant contributions to downwind ozone pollution by that date — or by any date, for that matter,” the three-judge panel wrote.

The court ruled that the open-ended compliance timeframe exceeded the bounds of the EPA’s statutory authority and allowed states to continue contributing to downwind states’ air pollution.

On Sept. 18, attorneys for the EPA asked the court to indefinitely delay oral arguments while the agency decides how to proceed.

Gormley said the ruling reinforces the action that the EPA should take to protect the nation’s air quality.

“The decision last week confirms a bedrock principle, and that is that the Clean Air Act requires EPA to achieve clean air in accordance with the standards it has already set by the deadlines in the act,” said Gormley. “It has to do it on time and, unfortunately, there are multiple areas, multiple types of air pollution, multiple regions of the country where EPA is not doing what it has to do to ensure clean air by the deadlines.”

The decision affected a similar case brought against the EPA by six states and New York City. The plaintiffs argued that the EPA was not doing enough to abide by the Clean Air Act’s “good neighbor” provision.

The EPA said it is considering rewriting a 2018 update to the rule. Attorneys representing the EPA asked the court to indefinitely delay oral arguments while it makes its decision. The court agreed to an Oct. 29 deadline for the EPA’s decision.

The Sierra Club ruling and the EPA’s decision in the second case could affect air quality and emissions in the state of Indiana. Under Indiana law, the state’s environmental rules board is prohibited from adopting a rule or standard that is “more stringent that the corresponding regulation or standard established under federal law.”

That means that what the EPA decides often becomes the standard the state will follow for environmental enforcement.

Since 2015, ozone levels in the state have increased significantly. The increase is most notable in the state’s industrial centers.

In Columbus, reported ozone days rose from 111 in 2015 to 242 in 2018. The Elkhart-Goshen area rose from 96 days in 2015 to 194 days in 2018. Indianapolis also experienced an increase in the amount of yearly ozone days. It jumped from 122 in 2015 to 145 in 2018.