WASHINGTON _ The Environmental Protection Agency took a major step to stimulate ethanol production by issuing a rule Thursday allowing ethanol plants to operate with fewer environmental rules and less air pollution equipment.

The agency rejected pleas by clean-air advocates and increased the amount of nitrogen oxide, sulfur dioxide and other pollutants that will be allowed before an ethanol plant is considered a "major air emitter," a category that requires more stringent re ulation. The change will increase the threshold for installing the best air pollution control equipment from 100 tons of pollution annually to 250 tons. It will also allow ethanol plants to avoid counting emissions from vents and other minor plant sources when t bulating those thresholds. The new rule would not apply in urban areas already dealing with air quality problems.

EPA spokeswoman Jennifer Wood said the rule was designed to make sure that all forms of ethanol production and the distillation of alcohol for human consumption "are treated equally under the Clean Air Act." Up to now, most ethanol plants have been treated like chemical manufacturers for purposes of air pollution regulation. The ethanol industry and its backers in Congress pushed hard for the new rule and the White House, a staunch supporter of biofuels, helped make the case for the change. Rick Tolman, chief executive officer of the St. Louis-based National Corn Growers Association, said the rule is beneficial to his members and a reflection of a trend toward larger plants.

"Even with the change, ethanol is significantly net positive for emissions and greenhouse gases," he said. Many local and state air-pollution officials opposed the change. They said the new rule will make their tasks more difficult in controlling pollution both from new ethanol plants and current plants that will be able to expand without installing pollutio -control equipment. "It was a double whammy. They have inappropriately increased the major source threshold and made that change worse by ignoring plant emissions that are still a problem for public health," said William Becker, executive director of the National Associati n of Clean Air Agencies, representing more than 200 air pollution control agencies in states and localities.

Frank O'Donnell, executive director of the nonprofit Clean Air Watch, said: "It's going to mean more dirty air and more disease." Missouri Gov. Matt Blunt was one of two governors who formally endorsed the rule change in a letter to the EPA. The second was South Dakota Gov. Mike Rounds. ___ (c) 2007, St. Louis Post-Dispatch. Visit the Post-Dispatch on the World Wide Web at http://www.stltoday.com/ Distributed by McClatchy-Tribune Information Services.