WASHINGTON, Jan 22 (Reuters) - The U.S. 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. Asarco LLC, which operates one of the three main U.S. copper smelters, was appealing a July decision by the D.C. Circuit Court of Appeals upholding the Environmental Protection Agency's new national ambient air quality standard for sulfur dioxide.