Sulfur dioxide emission curbs left intact by Supreme Court

The U.S. Supreme Court left intact federal limits on sulfur dioxide emissions from power plants and other industrial facilities, turning away an appeal by a copper- producing unit of Grupo Mexico SAB.

The justices today let stand a federal appeals court decision that upheld a 2010 Environmental Protection Agency rule setting the acceptable limit for sulfur dioxide in the air at 75 parts per billion over a one-hour period.

Grupo Mexico's Asarco unit argued unsuccessfully that the limit would impose unreasonable costs, requiring companies to spend $1.5 billion to comply. Another copper smelter, Freeport- McMoRan Copper & Gold Inc., said in court papers that it will have to spend hundreds of millions of dollars installing pollution-control systems at its Miami facility.

Asarco operates a copper smelter in Hayden, Arizona.

Five states joined Asarco in challenging the rule at the appeals court level. Only Asarco sought Supreme Court review. The Obama administration urged the high court to reject the appeal.

In tightening the sulfur-dioxide limits, the EPA pointed to research indicating that even short-term exposure can lead to respiratory illness. Power plants account for more than 70 percent of sulfur dioxide in the air, according to the EPA.