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Wildfire smoke now causes up to half the fine-particle pollution in Western US, study finds

Tony Barboza, Los Angeles Times on

Published in News & Features

"I hope that reducing the risk of climate change-related disasters, such as wildfires, will be a priority for the new administration," she added.

For decades, motor vehicles and industrial emissions have been responsible for most of the West's PM2.5, though at least some of that type of pollution has always come from fires. Previous studies have predicted that greenhouse gas emissions will dramatically increase wildfire smoke in the in the Western U.S. in the coming years as temperatures rise and dry the landscape.

In the latest study, Stanford and UC San Diego researchers predicted dramatic health impacts if nothing is done to slow climate change by slashing emissions and better managing forests. Within decades, they found, exposure to wildfire smoke alone could increase dramatically to the point of being one of the deadliest climate impacts.

The study projects an additional nine to 20 smoke-related deaths per 100,000 people by midcentury if emissions continue at their current pace, which is close to the roughly 24 additional deaths per 100,0000 people predicted directly from rising heat — the deadliest effect of climate change on people.

"Wildfires are going to be the way that many of us experience climate change, as important as these direct heat impacts," Burke said. "These changes in wildfire risk are the combination of two main things we have done: A century of wildfire suppression and climate change. None of these future estimates are an inevitability. They are a choice."

The analysis also found that while people of color continue to be exposed to higher levels of total PM2.5 — as has long been the case — higher-income counties with a higher proportion of white people are on average more exposed to higher levels of PM2.5 from wildfire smoke.


Researchers acknowledge that measuring outdoor pollution does not necessarily correspond to people's actual exposure because it does not factor in how much time they spend outdoors or the age and quality of their home. Past research shows that more outdoor pollutants seep into "older, smaller homes and for lower-income households and these differences could lead to disparities in overall individual exposure even if ambient exposures are not different," according to the study.

Scientists suspect the 2020 wildfires inflicted widespread health damage by fouling the air of nearly 96 percent of Californians with smoke levels exceeding federal standards, according to the state Air Resources Board. The weeks-long siege of smoky air generated both the highest readings and most widespread unhealthy levels of fine-particle pollution since continuous monitoring began in the late 1990s.

Of greatest concern are the microscopic particles in smoke that can be inhaled deep into the lungs and enter the bloodstream. Not only do those pollutants irritate the eyes, nose and throat, tighten the chest and cause difficulty breathing, they can trigger asthma attacks, strokes and heart attacks. Wildfire smoke poses serious risks to young children and the elderly, and people with chronic health conditions such as asthma, lung disease and heart disease face increased risk of hospitalization and death.

Scientists know from decades of research that breathing the fine-particle pollution in urban smog can lead to long-lasting health problems.

Though less is known about the long-term damage from the fine-particle pollution in wildfire smoke, early research suggests it impairs people's lungs long after the smoke clears. An ongoing health study in Montana reported last year that people in a community that was blanketed with wildfire smoke for 49 days in 2017 still had decreased lung function two years later.

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