US wildfires pushed ozone past legal limits

New Scientist: Legislate against pollution all you like, but don't expect nature to tow the line. Recent research on the wildfires that raged in California in 2007 shows that ground ozone levels were probably pushed significantly past legal "safe" limits.

[Ground level ozone] is responsible for a number of respiratory illnesses, ranging from coughs to bronchitis and emphysema. It also damages crops. Fires increase ozone levels by releasing nitrogen oxides, which form ozone when exposed to sunlight.

Gabriele Pfister of the US National Center for Atmospheric Research and colleagues focused on fires in California in September and October 2007. They used software to model the chemicals released by the fires and the ozone produced as a result. They also used climate models to show how these chemicals dispersed with the winds. They found that wildfires made it three times more likely that legislated levels be violated. And the effects were would have been far-ranging, reaching into Nevada, many miles away.

"Ozone can hit unhealthy levels even in places where people don't see smoke," says Pfister. "Wildfires are expected to worsen in the future, especially as our climate grows warmer. But we are only now beginning to understand their potential impacts on people and ecosystems – not only nearby but also potentially far downwind." The findings are likely to call into question suggested policies of letting natural wildfires burn themselves out instead of attempting to fight them. Those who advocate "let them burn" policies say wildfires are a natural ecosystem process.

Universal Studios fire, 2008, shot by pinguino k, Wikimedia Commons via Flickr, under Creative Commons Attribution 2.0 License