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The Devastating Effect that Wildfires have on Air Quality

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Driven by climate change, wildfires are on the rise. New studies highlight the burden of such events on communities and human health. 

Wildfire activity is on the rise across the globe due to the continuing effects of global warming. The joint warmest year on record, 2020, was a year of wildfires thanks to dry conditions and droughts, driven by climate change, with over 45 million acres of land lost in Australia alone. 

These configurations represent an increasingly devastating and often deadly burden. A new study conducted by researchers from Stanford University and the University of California and published in the journal PNAS¹ attempts to measure the societal burden of ferocious wildfires in the western United States. 

When wildfires are raging, the team found that toxic plumes of smoke severely affect air quality in these regions and could become climate change's most significant threat to human health and mortality.

This smoke pollution, which can last for weeks, is steadily undoing decades of efforts to reduce air pollution, doubling its contribution to poor air quality over the past 15 years. 

As a result, Marshall Burke, one of the study's authors and an associate professor of Earth Science at Stanford, believes that wildfires are among the main effects that individuals in the US experience climate change.

The Human Cost of Wildfires 

As a striking example of just how pressing a concern that wildfires are, in California alone during 2020, 4 million acres were burned, resulting in the destruction of over 10 thousand buildings, whilst hundreds of thousands of people faced mandatory evacuation, and at least 31 lives were lost. 

The economic cost of California's 2020 wildfires is yet to be calculated, but the state's 2018 wildfires cost the US economy was almost $150 billion dollars, 0.7% of the United States' annual GDP³, and last year's fires were even more damaging.

Of course, California wasn't the only region of the US ravaged by wildfires in 2020. Huge areas of Colorado, New Mexico, and Arizona were also razed by scorching fires. Looking worldwide, Australian bushfires led to what has been dubbed 'black summer' and caused massive damage to ecosystems.

Even more concerning, researchers are now predicting that deaths related to air pollution resulting from wildfire smoke could match or even exceed heat-related deaths. This would make deaths through smoke-related air pollution the biggest threat to mortality relating to climate change². 

The Effects of Wildfire Smoke on Human Health

Researchers still don't know the real extent of the health problems caused by this type of air pollution. The scientific consensus previously was that particulate matter air pollution — the mixture of solid particles and liquid droplets 30 times smaller than a human hair and officially categorized as PM2.5s  —  takes four months of lifespan off the average American. A recent study⁴ has shown that the problem could be even more extreme than this. 

Measuring hospital admissions over a six-year period from 2013 to 2018 researchers from the Desert Research Institute (DRI), the Renown Institute for Health Innovation (Renown IHI), and the Washoe County Health District (WCHD), found a significant increase in emergency room visits by people with asthma when smoke from wildfires was prevalent.

When framed in the context of the California wildfires, another Stanford team found a dramatic rise in hospitalizations for conditions like asthma, strokes, and heart attacks for Californians exposed to months of burnt orange and brown air filled with smoke particulates.

The team found an extra 500 people were admitted to hospitals in the Stanford area with a 14% increase in heart attacks and cardiac issues, an 18% increase in kidney issues, and an 18% increase in asthma admissions. The team's most concerning statistic was a disturbing 43% increase in hospitalizations resulting from strokes and other cerebrovascular conditions, possibly caused by inflammation resulting from smoke inhalation. The team expects that these figures will continue to rise. 

Wildfire Pollution Effects Everyone Equally

Whilst it may not come as a huge surprise that smoke from wildfires negatively affects the atmosphere and human health, this latest study shows just how extreme an impact these events are having. 

One surprise for the team involved in conducting the study was that these effects aren't just impacting low-income areas. Historically disadvantaged and poorer communities have felt the impact of air pollution more acutely as they are often situated more closely to industrial areas and major roadways. 

Smoke from wildfires, however, spreads over much broader areas than other pollutants. Additionally, the western parts of the US are regions of wealth relative to the rest of the US. Poorer people could still ultimately bear the brunt of this pollution however, when factors such as living in older homes that are less well protected against smoke pollution, and less access to healthcare are considered.

The team reached their conclusions by uniting satellite images of smoke plumes as they travel across the US with local data collected by ground-based air monitors. In order to combat difficulties in assessing the altitude of these plumes and thus if they are impacting air quality, the researchers used a statistical model that describes the dynamics of pollution in areas affected by wildfires.

One way to combat the spread of wildfires is to clear debris from dry forest flaws. Ironically, this could involve letting smaller forest fires burn under controlled conditions rather than immediately snuffing them out. 


¹ Burke. M., Driscoll. A., Heft-Neal. S., et al, [2021], 'The changing risk and burden of wildfire in the United States,' PNAS, []

² Yao. J., Brauer. M., Wei. J., et al, [2020], 'Sub-Daily Exposure to Fine Particulate Matter and Ambulance Dispatches during Wildfire Seasons: A Case-Crossover Study in British Columbia, Canada,' EHP, []

³ 'Full cost of California's wildfires to the US revealed,' [2020], [,state%20came%20to%20%2442.7bn]

⁴ Kiser. D., Metcalf. W. J., Elhanan. G., et al, [2020], 'Particulate matter and emergency visits for asthma: a time-series study of their association in the presence and absence of wildfire smoke in Reno, Nevada, 2013–2018,' Environmental Health, []

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Robert Lea

Written by

Robert Lea

Robert is a Freelance Science Journalist with a STEM BSc. He specializes in Physics, Space, Astronomy, Astrophysics, Quantum Physics, and SciComm. Robert is an ABSW member, and aWCSJ 2019 and IOP Fellow.


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