Western Wildfires Undermining Progress on Air Pollution

http://www.climatecentral.org/news/report-wildfires-undermining-air-pollution-progress-21753

Nov. 7, 2017

Smoke pollution is leading to serious public health impacts as large wildfires across the American West become more frequent and destructive. These fires are undermining progress made during recent decades in reducing pollution from tailpipes, power plants, and other industrial sources. The increasing frequency and area burned by large fires is linked to human-caused climate change as well as other environmental changes.

Climate Central analyzed air quality trends from 2000 through 2016 in two large California air basins that are heavily affected by smoke pollution. The analysis focused on particulate matter (PM2.5), a dangerous air pollutant. We found that while the air is getting cleaner overall in recent years, it’s getting dirtier during the fire season — a season that research has shown is growing longer in the western United States.

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Wildfires are a source of an especially problematic type of air pollutant known as PM2.5 (“particulate matter” less than 2.5 microns in diameter), which can become lodged in lungs and cause or exacerbate a wide array of health problems such as asthma and heart disease. Emerging evidence suggests PM2.5 could also be linked to premature births. Other PM2.5 sources include a wide variety of industrial and agricultural activities.

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Wildfire seasons are projected to become worse due to climate change, expanding in length and increasing the number of large fires and acreage that burns each year. When compared with the 1970s, the average annual Western U.S. wildfire season is now 105 days longer, has three times as many large fires (larger than 1000 acres), and burns more than six times as many acres.

According to the 2014 National Climate Assessment, warming temperatures and drier conditions are major factors resulting in the increase in wildfires; both temperatures and reduced moisture are linked to human-caused climate change and affect the dryness and flammability of landscapes, measured by scientists as fuel aridity.6 High levels of fuel aridity can provide large areas conducive for the spread of wildfire once ignited.

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Ecosystem changes and natural climatic variation can also have large influences on wildfire seasons. Even without human-caused climate change, wildfires would have increased in many regions due to other human activities and natural factors. In particular, although wildfires are a natural process in Western ecosystems, their roles in keeping forests in healthy condition have not been well understood, and so they are often extinguished as quickly as possible. As a result of strenuous efforts to suppress wildfire and other land-management practices such as livestock grazing, logging, and land-type conversion,8,9 many forests have experienced fire deficits, becoming overgrown and littered with flammable material such as leaf litter and saplings. Wildfires that break out during fire deficits can be unnaturally large and severe.10-12 In addition, the introduction of non-native species, especially invasive grasses, can have significant impacts on grassland wildfires as these plants can provide fuel for fires.

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Wildfire smoke can travel and affect communities hundreds of miles away from its source. The North Bay Fires affected air quality in the Central Valley and satellite images show it traveled more than 500 miles over the Pacific, reaching as far south as Mexico.19 In 2015, smoke from wildfires in central Canada resulted in multiple days of exceedances of EPA standards in Maryland.20 In 2002, wildfire smoke from fires in Quebec impacted populations all along the East Coast of the United States, and a nearly 50 percent increase in hospital admissions for respiratory diagnoses for the elderly was associated with the smoke plume and concurrent PM2.5 in counties in states between New York and Washington, DC.21

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