Toxic smoke from wildfires can travel thousands of miles, endangering people far from the flames.


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After a decade of record-breaking fire seasons, California suffered its worst ever recorded in 2020. Some 8,400 wildfires have incinerated more than 4 million acres, causing epic devastation. Six of the largest fires in the state's history occurred this past year, with the August Complex fire becoming the biggest of all. The smoke from these massive blazes caused harmful and, for some, life-threatening levels of air pollution in five northern California counties near San Francisco.

Figure. Air pollutio... - Click to enlarge in new windowFigure. Air pollution caused by the California wildfires can be seen over downtown San Francisco in September. Photo (C) Shutterstock.

Wildfire smoke is a volatile mixture of gases and particles containing thousands of compounds that can be chemically transformed in the atmosphere. Its exact composition depends on what is burning-forest, grass, structures-but the prevalence of PM2.5, particulate matter with a diameter less than 2.5 microns, exacerbates the health risks. These particles, smaller than a speck of pollen, are easily inhaled and absorbed into the bloodstream and can inflict lasting damage on the lungs, heart, kidneys, liver, and immune system.


This year's record-setting wildfires in California and the Pacific Northwest have contributed to the worst air quality in decades. Numerous studies show that even brief exposures to high levels of PM2.5 trigger spikes in coughing, asthma, heart attacks, strokes, and hospitalization. Long-term exposure to PM2.5 also shortens life expectancy. The World Health Organization estimates that fine particulate matter in the outdoor and household environments together produce 7 million premature deaths per year globally.


Exposure to even one wildfire can have lasting adverse health effects. In 2017, the Rice Ridge Fire cloaked the town of Seeley Lake, Montana, with 50 days of smoke. A team of researchers examined how long it would take for residents' lungs to fully recover, using spirometers to gauge lung function. Many residents learned their lungs never improved, and some worsened significantly one and two years after their initial exposure.


These findings have profound implications for populations most at risk for elevated air pollution, including seniors, people with chronic conditions, pregnant women, children, indigenous and migrant populations, homeless people, and firefighters. Elevated air pollution can weaken the body's immune system. Scientists at Harvard University found that even a small increase in PM2.5 levels was linked to an 8% increase in death rates from COVID-19.


Aside from the effects of breathing toxic air, wildfires can also cause posttraumatic stress and strip access to health care from those who need it most. Allyn Pierce, an RN and ICU manager at Adventist Health, witnessed this firsthand when the Camp Fire, California's deadliest wildfire on record, ripped through the town of Paradise in 2018. The fire left thousands homeless, and the damage forced the closure of Adventist Health's Feather River Hospital.


"Emotionally, there is a community-wide posttraumatic stress that I saw playing out differently for everyone depending on how direct their exposure was to the Camp Fire," Pierce told AJN.


Plumes of smoke containing pollutants from recent West Coast fires have traveled as far as the East Coast, potentially raising health risks for people living thousands of miles from the fires' source. Microscopic particles in wildfire smoke grow more poisonous the farther they travel because of the oxidation that occurs in the atmosphere. A study conducted in Greece showed that the toxicity of the smoke can double in the hours after it is first emitted and quadruple within days.


There is broad consensus that climate change is contributing to more frequent and extreme wildfires worldwide, from the Arctic to Australia. In the United States, the federal government's most recent National Climate Assessment predicts climate change will produce three times as many large fires by the mid-21st century. With each massive fire, health problems will likely persist long after skies clear.-Lucy Wang Halpern