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Report: Wildfires & Air Pollution, A Hidden Hazard

Research Report by Climate Central

Across the American West, climate change has made snow melt earlier, spring and summers hotter and fire seasons longer. One result has been a doubling since 1970 of the number of large wildfires raging each year. And depending on the rate of future warming, the number of big wildfires in western states could increase as much as six-fold over the next 20 years.

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Beyond the clear danger to life and property in the burn zone, smoke and ash from large wildfires produces staggering levels of air pollution, threatening the health of thousands of people, often hundreds of miles away from where these wildfires burn. The critical component of a fire’s smoke is so-called “fine particle” air pollution, which is a direct threat to human health even during relatively short exposures. And the pollution levels produced by these wildfires are extremely high: high enough to potentially increase mortality in susceptible populations, like the elderly and those with heart conditions, and increase emergency room visits for asthma sufferers and others with respiratory conditions.   

This analysis looks at air pollution from some of the largest wildfires in the West over the past 12 years.  

We found that:

Wildfires caused the worst air pollution day of the year in the affected areas, for all of the fires analyzed. And the worst day of the year was bad, often as bad or worse than air pollution levels in Beijing. In 9 of the 11 fires analyzed, particulate pollution from the fire made the air unhealthy to breathe for anyone, not just children and sensitive populations. 

Wildfires burning within 50-100 miles of a city routinely caused air quality to be 5 to 15 times worse than normal, and often 2-3 times worse than the worst non-fire day of the year. 

Reno, during the Rim Fire, August 2013

Beijing, average pollution, September 2013

This year has seen particularly bad examples. Grants Pass, Ore., experienced hazardous air quality this summer, caused by the Douglas Complex and Big Windy Complex fires burning in Southern Oregon. For nine days this summer, Grants Pass had air quality so poor that it was unhealthy for anyone to be outside. On five of those days, fine particle pollution was literally off the charts — higher than the local air quality meter could read. 

Big metro areas are also susceptible to wildfire pollution. At least twice in the past 12 years, cities like Los Angeles, San Diego, and Riverside, Calif., have seen Beijing-level air pollution caused by wildfires burning in southern California. 

Rapidly warming spring temperatures and a shrinking snowpack make for a longer fire season, up to two months longer on average across the West. Hotter summers dry out the forest more rapidly and intensely than in the past, and fire suppression practices have increased the fuel supply, further increasing the risk of large, intense fires. Exposure to fine particulates in wildfire smoke – particles about 30 times smaller than the width of a human hair – pose a significant health risk for anyone, but particularly children, the elderly, and people with existing respiratory problems. They can penetrate deep into the lungs, increasing the mortality risk and health and lung problems, according to the U.S. EPA. As we continue to warm the planet, wildfires will increase in intensity and size, causing an increasing number of severely unhealthy air pollution days that in turn increase mortality in the elderly and those with heart conditions, while sending a growing number of children and sensitive people to emergency rooms in respiratory distress. 

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