UPDATE 1-U.S. top court rejects Asarco challenge to EPA rule
* Grupo Mexico unit objected to sulfur dioxide standard
* Sulfur dioxide linked to respiratory problems
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.
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".
A broad grant of rulemaking authority has financial implications for companies, to the extent they are forced to spend more to comply.
Asarco contended that the sulfur dioxide standard adopted by the EPA in 2010 was too stringent, rather than "not lower or higher" than necessary as it said was required under Supreme Court precedent.
But it said the D.C. Circuit did not follow this precedent, and instead gave the EPA an effective license to set needlessly tough standards. It said the sulfur dioxide standard may cost industry participants $1.5 billion.
In upholding the new standard, the D.C. Circuit said it lacked jurisdiction to review the EPA's rulemaking, and that the agency did not act arbitrarily.
Sulfur dioxide is typically the result of fossil fuel combustion at power plants and other industrial facilities, and has been linked to respiratory problems.
The EPA had first set sulfur dioxide standards in 1971, but in 2010 revoked them and established a new one-hour standard at a level of 75 parts per billion. .
The U.S. Department of Justice had urged the Supreme Court not to accept Asarco's appeal.
The case is Asarco LLC v. U.S. Environmental Protection Agency et al, U.S. Supreme Court, No. 12-510.