COLUMBUS, Ind. The technology being used by diesel engine-maker Cummins Inc. to meet 2010 federal emission standards has been targeted for additional study by the U.S. Environmental Protection Agency, a step that could have a serious impact on the motorcoach industry.

The EPA said in a letter to Cummins and other manufacturers that it plans to conduct independent tests to determine if engines using "copper zeolite" technology to reduce nitrogen oxide emissions emit dioxins that could be harmful to humans.

And, it warned that the engines could be rejected for federal certification if the test results are inconclusive or if they show increased dioxin emissions and the manufacturer is unable to show otherwise.

Cummins has been conducting its own tests and said its confident of its technology, according to spokeswoman Carol Lavengood. "Our engineering community feels really confident of the results we have seen so far," she said.

The motorcoach industry is watching the situation because Cummins soon could be the main or only engine source for many of the new coaches available to operators in the United States and Canada.

Thats because, beginning in 2010, Detroit Diesel Corp. plans to sell only to companies affiliated with Daimler, including Setra of North America Inc.; Caterpillar is getting out of the on-highway market altogether, and Prevost Car is switching exclusively to Volvo engines, made by its parent company.

That could leave some motorcoach manufacturers with one engine supplier Cummins.

Officials of the USEPA say theyre concerned about the use by Cummins of copper zeolite in its SCR catalytic converters, which limit NOX emissions to levels that meet the 2010 EPA standards. Other engine manufacturers are using iron zeolite in their SCR converters.

"EPA has a long-standing concern that copper has the potential to catalyze dioxin formation in conditions experienced in incinerators and in diesel exhaust," Karl Simon, director of the agencys Compliance and Innovative Strategies Division, wrote in the letter. "Therefore, questions have been raised regarding the potential for copper containing diesel SCR catalysts to promote the formation of dioxin compounds."

Dioxins long have been characterized by EPA as likely human carcinogens and are believed to harm the immune and reproductive systems and increase the risk of cancer. "An increase in dioxin emissions from any source sector is considered a potentially serious issue by the EPA," Simon noted.

Lavengood said Cummins was not surprised by the notice it received from the EPA and is cooperating with the agency. "We have been working with the EPA for quite some time on this," she said. "Any time we introduce new technology, we do testing and discuss it with them. Its part of the process."

She said company officials plan to review results of its tests with EPA representatives. "We are confident we will not see any issues with the use of copper," she stressed.

In a news release issued shortly after receiving the EPA letter, Cummins reaffirmed that its entire on-highway product range of engines will be ready to meet the 2010 EPA rules for emissions.

"The engines are already being built off our production lines for customer field tests, Jim Kelly, president of Cummins engine business said in the release. "Were getting great feedback from our field tests, and our products, our people and our customer support are ready for 2010."

He said the engine line will include a new lightweight, medium-bore engine the ISX11.9 for motorcoaches and some trucks and other vehicles.

Meantime, the EPA said it will hire an independent firm to evaluate the use of copper zeolite in the catalytic converters and the tests will get under way soon. It will involve testing an engine over several operating cycles using both copper zeolite and iron zeolite catalysts.

"If the data are inconclusive or show increased dioxin emissions, then EPA likely will not certify an engine family utilizing such products unless a manufacturer can provide data which demonstrates the intended use of the copper catalyst doesnt increase dioxin emissions, the EPA said. "Emission test data provided for this purpose must have been conducted using sound sampling and testing protocol."