From: Richard Harris, NPR, Environmental Health News, More from this Affiliate
Published January 31, 2010 09:40 AM

New Ozone Standards could contribute to warming

The Environmental Protection Agency's proposal to tighten the ozone standard for smog will have an unfortunate side effect: Because of a quirk of atmospheric chemistry, those measures will hasten global warming.

There's no question that smog is a hazard that deserves attention. Lydia Wegman of the EPA says the new ozone limits would have significant health benefits.


Less smog means fewer asthma attacks, fewer kids in the hospital, fewer days of lost school, "and we also believe that we can reduce the risk of early death in people with heart and lung disease," she says.

Here's the tough part: The way many states and localities will reduce smog is by cracking down on the chemicals that produce ozone. And those include nitrogen oxides, or NOx.

But Jason West at the University of North Carolina in Chapel Hill says that when you reduce NOx, you don't just reduce ozone; you change the chemistry of the atmosphere in such a way that you end up increasing the amount of methane in the air. And methane is a potent gas when it comes to global warming.

"By reducing NOx, the net effect is you make global warming worse," West says.

In fact, you could make warming a lot worse. If you got rid of all NOx and a related sulfur compound, that action alone would be enough to increase the Earth's temperature by 2 degrees Celsius — and that's in the danger zone for the climate, according to many scientists and governments.

U.S. pollution control laws are moving us gradually in that direction. The EPA estimates that by 2020, when the ozone standard will start to make a real difference in air quality, the result would be the reduction of 4.3 million tons of NOx per year — a reduction in emissions of 33 to 40 percent.

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