How Do Wildfires Affect Air Quality Levels?

Pollution from wildfires throughout Australia and California over the years has greatly affected air quality levels.  Pictures like the one above show the large amounts of smoke and pollution produced by these wildfires.

But how exactly does the smoke from these wildfires affect air quality levels?  What exactly is in wildfire smoke?

What Type of Air Pollution Is In Wildfire Smoke?

As it turns out, there are a lot of things in wildfire smoke.  According to the Environmental Protect Agency:

Smoke is composed primarily of carbon dioxide, water vapor, carbon monoxide, particulate matter, hydrocarbons and other organic chemicals, nitrogen oxides, trace minerals and several thousand other compounds.

But what pollutants should you be most concerned about?

Ultra-fine Particulate Matter (PM 2.5)

Wildfires create large amounts of ultra-fine particulate matter such as PM 2.5 and smaller.  These tiny particles are a major health concern.  Particulate matter are particles (solid or liquid) small enough to be absorbed directly to our bloodstream and enter our lungs, heart, and brains.

Unfortunately, wildfire smoke is comprised largely of these dangerous ultra-fine particles!


How large are these tiny particles in wildfire smoke?  It turns out, most wildfire particulate matter is extremely small, smaller than 1 micron.  These small particles are more dangerous than large particles as they can penetrate deeper into your organs.

But how small is 1 micron? Below shows a PM 2.5 particle, larger than most particles in wildfire smoke. It makes a strain of hair look gigantic!


Volatile Organic Compounds (VOCs)

As a wildfire burns, it produces dangerous VOC gases.  These VOC gases from wildfires include: ethane, aldehydes, benzene, toluene, ethylbenzene, xylene, formaldehyde, and acetaldehyde.

Breathing VOC gases found in wildfire smoke can have serious health affects.

Health affects of VOC gases from wildfire smoke include:

  • Eyes, nose, and throat irritation
  • Respiratory and neural problems
  • Cancer

Other Toxic Gases

Wildfire smoke can contain other toxic gases including sulphur dioxide (SO₂) , nitrogen dioxide (NO₂), ozone (O3), and carbon monoxide (CO).

 In general, these toxic gases are only a concern if you are in close proximity to the smoldering fire.  If this is the case, be careful!  Close proximity to the smoldering fire will have higher levels of all of the dangerous pollutions above.  Furthermore, carbon monoxide is deadly.


Closer Look: How Do Wildfires in Australia and California Affect the Air Quality?

In 2020, Australia and California experienced record-breaking wildfires.  How did these wildfires affect the air quality?

Australia Bushfires

In Australia, the bushfires of 2019-2020 caused air quality levels to exceed hazardous levels in the southeastern states of Victoria and New South Wales. This was primarily caused by the ultra-fine particulate pollution (such as PM2.5 and PM10) in the smoke.

The chart below shows the daily average PM2.5 air quality levels (AQI) for Canberra, Australia. During the worst of the bushfires in December 2019 and January 2020, the air quality was abnormally high, reaching hazardous levels.

The air quality got so bad in Australia from the bushfires that University of Tasmania environmental health professor Fay Johnston said more than 4,000 people were hospitalized from the smoke.

California Wildfires

In 2020, California had one of its most severe and deadly wildfire season in history.  The fires directly killed 37 people. However, this might not even be the worst of the fires.  The poor air quality from the wildfire smoke affected millions on the west coast of the US.

The air quality across the west coast from the California wildfires reached its worse levels in September of 2020.  Due to the wind direction, Portland and Seattle saw the worst of it, with days averaging hazardous air quality levels.  In September, this poor air quality from the California wildfires ranked Portland as the most polluted city in the world.

Portland, Oregon daily average PM 2.5 pollution for 2020. 


Visualize: How Bad Air Quality Gets From Wildfire Smoke

To get an idea of exactly how wildfires affect air quality, below are two PM 2.5 pollution concentrations for comparison.  This shows exactly how much of these dangerous ultra-fine there are in the air.  The more particles, the more dangerous pollution you are breathing in!


Relative to Portland’s air quality during the wildfires, NYC’s worst day looks pretty good! However, the reality is even 42 µg/m3 is over 4 times greater than the WHO recommended limit.  Moreover, Portland’s pollution concentration shown below was 47 times greater than the limit!


Bottom Line: How do wildfires in Australia and California affect air quality levels?

Wildfire smoke is full of dangerous pollution that can quickly spread to surrounding areas and create hazardous air quality levels.  These include:

*Small particulate matter (including PM2.5 and smaller)

*VOCs (ethane, aldehydes, benzene, toluene, ethylbenzene, xylene, formaldehyde, and acetaldehyde)

*Other toxic gases including sulphur dioxide (SO₂) , nitrogen dioxide (NO₂), ozone (O3), and carbon monoxide (CO)

Written by Michael Cole

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