Air pollution knows no borders, recognizes no state lines or city limits. Particles from one of the almost 50 coal plants in Pennsylvania do not stop in their tracks when they reach New Jersey (even if the state’s citizens might).

In August 2011, the Environmental Protection Agency finalized the Cross-State Air Pollution Rule (CSAPR) to reduce the flow of pollution from 28 states to their downwind neighbors, estimating that its implementation would prevent up to 34,000 premature deaths. But 15 of those states challenged the law, and today, a divided U.S. Court of Appeals for the D.C. Circuit ruled in their favor, striking down the law and the limits it put on sulfur dioxide and nitrogen oxide emissions from power plants. By requiring states to reduce emissions beyond their own contributions, the court said, the EPA went beyond its legal authority. It also found that the ruling violated the Clean Air Act by not allowing states to propose their own pollution control plans.

In her 44-page dissent, Judge Judith Rogers chided the majority for straying from its past precedents and ignoring the “plain text of the Clean Air Act,” whose Good Neighbor provisions allow the agency to limit emissions that cross state borders.

Unsurprisingly, industry leaders and Republican politicians cheered the decision. Though Pennsylvania was not one of the states filing suit, state Sen. Pat Toomey stated said he was “pleased with today’s decision and hope[s] it will send a strong message to the EPA as it reconsiders its regulatory approach.” While some emphasized the decision’s importance in allowing states to handle pollution themselves, without interference from the federal government, others saw it as just a delay. Doug Biden, president of the Electric Power Generation Association in Pennsylvania, said “Some power plants in places like Texas may be breathing easier, and it may buy some time for a few here in Pennsylvania, but I don’t see a lot benefiting because many have already put in controls.”

In addition to the predicted health benefits of the law, the EPA also expected it to cut sulfur dioxide emissions by 73 percent and nitrogen oxide by 54 percent. So while power plant executives may be breathing easier, the people living in those states are not. Whether the EPA will draft a new rule or appeal the court’s decision is yet to be seen. In the meantime, emissions will continue as usual.

Main photo credit: Geograph