Several states are pursuing limits on diesel engine emissions separately from federal controls, The Associated Press reported recently.

The standards, which are based on California’s, are designed to take the place of federal standards for the year 2007 that states fear will be weakened or delayed, the news service said. The report did not specify which states are considering the tougher emissions measurements, but Bill Becker, who works with state and local air pollution control officials, told the news service, "I would expect dozens of states to pursue the adoption of California standards."

The current diesel emissions standards are about 8 percent of pre-1990 emissions. By 2007, diesel engines will require emissions run about 4 percent of current levels. By 2010, emission will be required to be 99.2 percent lower than those allowed in 2002 to 2004.

Despite the effort, California-style standards are not a shoe-in – AASHTO reported recently that lawyers for the makers of diesel-powered vehicles and the petroleum industry have taken their case against those standards to the U.S. Supreme Court.

In oral arguments before the court recently, those attorneys challenged clean-air standards imposed in California as being in conflict with the federal Clean Air Act because they are tougher than that law, The Associated Press reported.