Over the last few years, various states, cities, counties, and municipalities have issued warnings about the health risks of wildfire smoke during wildfire season. We know that air pollution is harmful to inhale, but how does wildfire smoke differ from more common pollutants, and what makes it so dangerous?

We know that wildfire smoke makes up nearly half the air pollution measured annually in the western United States. In a study from the California Air Resources Board, released July 12, 2022, researchers found that smoke from wildfires that burn through communities can be more toxic than initially thought due to the building materials that can burn. These same researchers found high levels of lead and other metals in smoke from the fire that burned through Paradise, California, in 2018.

In an announcement from the National Interagency Fire Center (NIFC), there have been over 25,000 wildfires that have burned 1.4 million acres as of May 2022. This surpasses the 10-year annual average for the number of fires by over 6,000 fires. Climate change, heat, drought, and severe storms are the forerunners of making wildfire conditions worse.

What is wildfire smoke?

With all these fires, it’s important to know what exactly is in wildfire smoke and how it can differ from fire to fire. Three main factors determine what’s in wildfire smoke: what’s burning, the temperature of the fire, and the distance between the person inhaling the smoke and the fire producing it.

As you get further away from the source of a wildfire, the distance allows traveling smoke to age. This means that the sun and other chemicals in the air can make the smoke more toxic. Large particles and pollutants like ash don’t typically travel that far away from the fire, but smaller particles and contaminants can travel long distances and even across continents.

Wildfire smoke contains countless individual compounds, such as carbon monoxide, carbon dioxide, hydrocarbons, nitrogen oxides, and volatile organic compounds. After the Paradise fire in 2018, researchers found dangerous levels of lead in smoke blowing downwind from the fire. These particles traveled more than 150 miles on the wind alone! The most common pollutants by mass are particulates less than 2.5 micrometers in diameter, about 50 times smaller than a grain of sand. When public health authorities issue air quality warnings, they use PM2.5 as the benchmark metric.

So, what does wildfire smoke do to our bodies?

 The PM2.5 metric mentioned above serves an essential purpose; it defines the cutoff for particles and pollutants that can travel deep into our lungs and cause the most damage. Any particles bigger than PM2.5 is met with our natural defense systems, meaning our bodies will naturally defend us against these particles. The smaller particles bypass our bodies’ defenses and disturb our lungs’ air sacs, where oxygen crosses into our blood. Thankfully, we have immune cells present called macrophages. These cells seek out foreign materials and remove or destroy them. However, wildfire and wood smoke exposure can suppress these cells and increase lung inflammation.

Long-term and repeated exposure to wildfire smoke can cause lung damage and may also lead to cardiovascular problems. Recent studies suggest that long-term exposure to these small particulates can make the coronavirus more deadly. A nationwide study found that a slight increase in PM2.5 from one U.S. County to the next was associated with a significant increase in the death rate from Covid-19.

What can you do to stay safe and protect your health during wildfires?

The best answer is to stay informed! Keep up with your local Department of Natural Resources, NOAA, and NIFC, and listen to public health officials’ announcements and warnings regarding wildfire smoke. If your area has an air quality warning, try to avoid being outside or doing strenuous activity. Note that not all face masks protect against smoke particles!

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