SPRINGFIELD - Cleaning up car exhaust could reduce toxins in the air by about 20 percent in 20 years, a study released Tuesday suggests.

The study was released as part of a push Tuesday by environmental groups asking Illinois lawmakers to raise pollution standards on cars sold in the state over the next decade or so.

"Cleaner cars on the roads mean cleaner air for our children to breathe," said Howard Learner, director of the Chicago-based Environmental Law and Policy Center.

Illinois legislation has stalled since last year, though other states have raised standards, perhaps most famously in California in the early 1990s.

If Illinois was to follow, the federal Environmental Protection Agency would have to sign off. The agency recenly declined California's request.

Environmental officials said they don't think that will be a problem, as the case is tied up in court and incoming presidential candidates have promised to overturn that decision.

Opponents say allowing individual states to set gas mileage and pollution standards separate from the federal government can cause problems, essentially forcing manufacturers to follow different rules for different states.

"Our approach is there should be a national approach rather than state by state," said Joe McMahon, spokesman for the Illinois Automobile Dealers Association.

The plan would force manufacturers to build cars that met certain standards that would increase over time. But people who own older cars not up to snuff wouldn't be required to make costly repairs to their vehicles to meet standards.

The legislation is House Bill 3424 and Senate Bill 2238.