A better way to mange smog.

Although the numerous volatile organic chemicals (VOCs) that generate smog ozone don't all operate with the same efficiency, current federal regulations aimed at controlling smog provide no incentives for polluters to eliminate the most potent VOCs first, notes a team of researchers in the July 28 Science. Indeed, their new analysis indicates, ozone problems could actually worsen if, in the process of cutting total VOCs, polluters substituted highly reactive ones for barely reactive alternatives. In contrast, they argue, regulating VOCs on the basis of reactivity could as much as double the ozone reduction achieved per dollar spent to control them.

California already ranks--and regulates--VOCs this way as part of two vehicle-emissions programs. And while the federal government should too, says analysis coauthor Armistead Russell of Carnegie Mellon University in Pittsburgh, it should not stop there. Russell would reward all polluters for reducing the overall reactivity of the VOCs they emit--from industrial plants and consumer products such as paints to any companies that signed onto the smog-emissions trading program proposed by EPA last week. The latter would allow a VOC emitter to buy a "credit" to pollute from a company that had already reduced its emitted VOCs more than regulations required.

Some critics have argued against such a policy, on the grounds that an individual VOC's reactivity can vary with climate, typical cloud cover, even prevailing, coincident pollutants. But Russell says his team's new analysis found that these factors don't matter much: Whatever alters the reactivity of one VOC does much the same thing to most of the rest. So volatility differences between VOCs change little.