The Supreme Court has declined to hear an appeal on an U.S. Environmental Protection Agency rule limiting sulfur dioxide (SO2) in the air to 75 parts per billion over one hour. SO2 is a result of fossil fuel combustion, often produced at power plants.
According to Reuters, the current SO2 limits, set by the EPA in 2010, was challenged by Grupo Mexico SAB’s Asarco LLC unit. The Supreme Court chose to not hear the appeal without comment after a federal appeal court upheld the EPA rule.
Asarco, which runs one of the three main copper smelters in the United States, has estimated the rule could cost companies $1.5 billion.
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