By Jonathan Stempel
WASHINGTON | Tue Jan 22, 2013 10:36am EST
(Reuters) - The Supreme Court on Tuesday refused to consider an appeal by Asarco LLC over how much authority a top federal environmental regulator should have in setting air quality standards.
Without comment, the Supreme Court decided not to hear the appeal of Asarco, a unit of Grupo Mexico SAB that operates one of the three main U.S. copper smelters.
Asarco had been appealing a July decision by the Washington, D.C., Circuit Court of Appeals that upheld the Environmental Protection Agency's new national ambient air quality standard for sulfur dioxide.
The EPA is authorized under the Clean Air Act to adopt standards that are necessary to protect the public health, while allowing an "adequate margin of safety".