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More wildfire, more bad air

August 6, 2009 |  1:05 pm


An expected rise in wildfire in coming decades is bad news for western lungs.

Harvard University scientists are predicting some forms of air pollution could increase significantly across the West as more of the region's wildlands burn as a result of rising temperatures.

Smoke from wildfires contains two main kinds of carbon particles: black soot, or elemental carbon, and lighter-colored particles, called organic carbon aerosols, which are a mix of chemicals.

"In large quantities, downwind of fires, organic carbon aerosols are hazardous," said senior research fellow Jennifer Logan, who led a study examining rising wildfire rates and the impact on air quality. "The particles irritate lung tissue and the chemicals they carry are toxic. But even at low concentrations, these aerosols may be dangerous. We don't know. There is no known threshold where damage begins."

The research, published in the June 18th issue of the Journal of Geophysical Research, estimates that summertime levels of carbon aerosols could rise 40% across the West between 2000 and 2050. Concentrations of elemental carbon could increase 20%.

In areas facing more dramatic wildfire increases, such as the Sierra, the Pacific Northwest and the northern Rockies, carbon aerosol production will be even greater.

Studies in recent years have linked rising temperatures associated with climate change to growth in wildfires in some parts of the West. Warmer weather lengthens the fire season and dries out forest growth.

Using a series of models, Logan and her colleagues at Harvard's School of Engineering and Applied Sciences predicted that the amount of land typically burned in the West could jump by roughly 50% by the 2050s compared to the present-day.

That in turn will ramp up smoke production, hurting air quality and visibility. 

"Our model cannot calculate individual fire events in the future," Logan wrote in an e-mail. "But based on our results, we would project that many more communities will be subjected to unhealthy air quality from fires by the 2050s."

-- Bettina Boxall

Photo: Thick smoke from a 2004 wildfire near Lake Tahoe. Credit: Associated Press