BILLINGS, Mont. (AP) — A federal appeals court has struck down pollution rules intended to reduce haze in the atmosphere from the burning of coal in Montana for electricity consumed across the Pacific Northwest.

Haze reduces visibility and is caused by nitrogen oxide and sulfur dioxide pollution. The Clean Air Act requires companies to use the best available technology on older coal plants to reduce the pollutants.

But a three-judge panel of the 9th U.S. Circuit Court of Appeals said the Environmental Protection Agency would arbitrarily require PPL Montana to install pollution controls costing tens of millions of dollars, without assurance of improvements.

Tuesday's ruling applies to the 2,100-megawatt Colstrip plant and a second plant in Billings that recently shut down. PPL Montana was spun last week off to form Talen Energy.