Choking Off Air Quality

Last summer was the smoggiest in the Los Angeles Basin in six years. And this week, a brown haze again enveloped City Hall and the local hills as temperatures soared. Along with these setbacks, Southern California’s effort to clean the air is once again under attack, this time by the U.S. Supreme Court.

Unhappily, the court decided Wednesday that a regional clean-air board had overstepped its authority by ordering vehicle fleet operators -- public and private -- to buy cleaner-burning trucks and buses as they replace dirty diesel vehicles.

The justices held that the federal Clean Air Act trumps the stronger rules of the South Coast Air Quality Management District. Heaven forbid, the court said, that local rules might proliferate.

To date, the rules have put more than 5,500 clean-fueled and lower-emission vehicles on the road in Los Angeles, Riverside, San Bernardino and Orange counties, most of them powered by natural gas. That’s 5,500 city buses, trash trucks, school buses, airport shuttles, taxis, street sweepers and heavy-duty utility trucks that don’t trail plumes of black soot.

Diesel vehicles contribute 23% of all nitrogen oxide emissions, a key smog ingredient. Moreover, according to the Environmental Protection Agency, the tiny particles in diesel exhaust clouds can cause lung cancer, asthma and a host of respiratory problems.

The manufacturers of heavy-duty diesel engines, angry about potentially reduced sales, brought the lawsuit the court ruled on Wednesday. The Bush administration could have stayed out of the fight but instead filed a friend-of-the-court brief on the engine makers’ side.

In an 8-1 vote, the court bought the argument that in adopting the fleet rules, the local air agency had exceeded its authority because the rules, in effect, set emissions standards. The Clean Air Act allows only the federal government to set emission standards. The AQMD had argued that the rules only set requirements governing vehicle purchasing.

Thirty years ago, the L.A. Basin’s miserable smog prodded Congress, when it amended the Clean Air Act, to let the state of California ask for exemptions from federal rules so it could impose tougher emissions standards. Clean Air Act language pushes the EPA to grant such waivers in most cases. That’s why California set more stringent air-quality standards for automobiles and why automakers now sell cars across the nation that meet California’s standards.

The AQMD didn’t ask for waiver authority when it passed the fleet rules. At minimum, the court’s decision should prod the AQMD’s board to enlist the state Air Resources Board to ask for such authority on the local agency’s behalf when it meets next week. Air in the Los Angeles Basin is still the smoggiest in the nation -- and getting worse after steady years of improvement.

The regional rules that steadily reduce diesel exhaust shouldn’t choke in a federal noose.