The court stated the EPA cannot ban HFCs under Section 612 of the Clean Air Act because that provision was designed only to address ozone-depleting substances.

Recently, the U.S. Court of Appeals for the District of Columbia Circuit (one of the courts below the U.S. Supreme Court and the court that is charged with reviewing many EPA Clean Air Act rules) issued a divided decision to EPA's efforts to cut emissions of HFCs in the United States.

That means that just one kilogram of an HFC is the equivalent of 1.7 tons of carbon dioxide pollution, said Paul Blowers, a chemical engineering professor at the University of Arizona.

Two companies that manufacture products with HFCs filed suit in 2015, asking the court to strike down the rule.

Using the Clean Air Act to comply with the protocol, the EPA chose HFCs to replace ozone-depleting chlorofluorocarbons, or CFCs, in aerosol cans and refrigerators - the main cause of the ozone hole.

To the EPA, companies are still replacing their ozone-depleting chemicals with HFCs today, even if they made the decision to switch 20 years ago.

Brendan Collins, an environmental attorney and a partner in Ballard Spahr's Philadelphia office, said this may indicate the judges in the majority are sympathetic to the EPA’s goals here.

David Doniger of the Natural Resources Defense Council, which intervened on behalf of the EPA, said the U.S. NGO is "exploring all options for appeal." The company planned to spend $880 million on research and development to replace its HFCs. "EPA would thereby have indefinite authority to regulate a manufacturer's use of that substitute."

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