Washington (Platts)--20Jul2012/305 pm EDT/1905 GMT

A federal court ruled Friday that the US Environmental Protection Agency has legal authority to regulate sulfur dioxide at intense levels to protect public health, even when air quality meets national standards.

The US Court of Appeals for the District of Columbia Circuit drew that conclusion in an order dismissing and denying petitions from states, corporations and a multi-sector manufacturing trade group that challenged EPA's "Primary National Ambient Air Quality Standard for Sulfur Dioxide."

In its opinion on National Environmental Development v. EPA, the court said EPA did not act arbitrarily in setting the standard that targets short-term bursts of SO2 exposure. The 2010 rule regulates SO2 in addition to the existing national ambient air quality standard for sulfur, which is emitted by fossil-fuel generation and other industrial activities and contributes to acid rain.

"We have held before that EPA has discretion to set a NAAQS at a concentration level below a level that has been demonstrated to have a statistically significant association with negative health effects," Chief Judge David Sentelle wrote for the court. "Just so now."

Joining Sentelle on the DC Circuit panel were Senior Circuit Judge Douglas Ginsburg and Judge Brett Kavanaugh.

Environmental and health advocates praised the decision. "Today's judicial decision strongly affirms that EPA's clean air protections addressing dangerous sulfur dioxide are firmly grounded in science and the law," said Peter Zalzal, staff attorney with Environmental Defense Fund.

"These standards help protect the public health and are especially important for the most vulnerable, including more than 25 million people with asthma," said Paul Billings, vice president of National Policy and Advocacy with te American Lung Association. Both EDF and ALA intervened in the case to support EPA's regulation.

--Cathy Cash cathy_cash@platts.com

--Edited by Valarie Jackson, valarie_jackson@platts.com