Increasingly fierce forest fires in the western United States are having a devastating impact on the region’s air quality, with smoke from the fire accounting for half of all air pollution during the worst years of forest fires, according to one new study.
Scientists at Stanford University and UC San Diego have found that toxic clouds of smoke, which can cover western states for weeks when forest fires are intense, are reversing decades of gains in cutting air pollution. Although heat-related deaths were previously predicted to be the worst consequence of the climate crisis, the researchers say air pollution caused by smoke can be just as deadly.
“For many people in this country, forest fires will be the way they experience climate change,” said Marshall Burke, associate professor of earth sciences at Stanford and one of the study’s authors. “The contribution of forest fires to poor air quality has almost doubled in the last 15 years in the west.”
Air pollution by fine particles, known as PM2.5s, was already known to take four months out of the average American’s life span. And health researchers are just beginning to understand the distressing health consequences added by increasing smoke exposure for a wide range of the population in the United States.
Seasons of forest fires have become increasingly brutal in the American West, exacerbated by the climate crisis. The fire storms of 2020 were among the worst in recorded history, with 31 people killed, 10,000 buildings destroyed or damaged and more than 4 million hectares burned in California alone. Large areas of Colorado, New Mexico and Arizona were also burned.
After California residents endured a month of orange-brown air filled with small, dangerous particles, another group of Stanford researchers tracked dramatic increases in hospitalizations for things like strokes, heart attacks and asthma.
Bibek Paudel, a postdoctoral researcher at the Stanford asthma clinic, found that hospitalizations for strokes and related illnesses increased by 60% in the five weeks after lightning fires started sending smoke across northern California last August . The number of lost pregnancies also doubled in the weeks after the fires – an astonishing finding that researchers are still interpreting. Paudel also found significant increases in heart attacks and hospitalization of young people for respiratory diseases.
“I don’t think people are aware of the long-term health effects of smoke from forest fires,” said Mary Prunicki, research director at the Sean N Parker Center for Allergy and Asthma Research at Stanford.
For decades, air quality in the United States has improved due to the reduction in pollution from cars and factories, required by the Clean Air Act. But in the past 40 years, the amount of land burnt in forest fires has quadrupled, Burke’s study found.
The study, published in the Proceedings of the National Academy of Sciences, combined satellite imagery of plumes of smoke with measurements taken from ground air monitors, which record local air pollution, to model total smoke exposure. The study covered all states west (and inclusive) of New Mexico, Colorado, Wyoming and Montana.
Plumes of smoke can be detected by satellite images while traveling across the country. But it is difficult to say whether they are low enough to affect air quality on the ground, so the study created statistical models of how pollution changed at specific locations after fire events, combining information from satellites, air monitors and air models. Dice.
“Everyone knows that forest fires produce dirty air – so that’s not surprising,” said Burke. “What we managed to do in this study was to quantify how big that contribution is. And we found that it is really reversing much of the progress that has been made across the country in improving air quality. “
Surprisingly, the study found that smoke from the fire is spreading the effects of air pollution to whiter and wealthier populations. Historically, low-income communities have been most affected by air pollution, usually because their homes are closer to highways and factories. But the smoke spreads pollutants over much wider areas. Burke said the western United States, where most forest fires occur, also tends to be whiter and richer than other parts of the country.
As plumes travel across the country, pollutants can harm even people who live far from fires, in the Midwest or East.
“The smoke from forest fire is a burden that is much more equally shared than pollution,” said Burke.
However, other research has shown that low-income populations can be hit harder when smoke covers a region, because their smaller, older homes offer less protection.
Ironically, one of the future solutions to all this smoke may be to light more fires.
The increase in forest fires is partly due to higher temperatures and drier conditions, but there is a growing consensus that it is also a result of the country’s fire suppression policy, rather than occasionally letting the land burn.
“There is a lot of fuel on the ground,” said Burke. “Climate change is drying up and making it much more flammable.”
Burke said a policy for using prescribed fires, which involves lighting carefully controlled fires to clear some of the shrubs, could be an important strategy for reducing forest fires and decreasing exposure to dangerous smoke in the coming years.
“The benefits can be very big, but there are a number of key issues that need to be studied,” he said.
Otherwise, “under the usual business regime, years like 2020, which historically have been out of the ordinary, can become much more common,” he said. “It’s kind of terrible to think about it.”