The record-breaking 2020 fire season for the western United States has caused many to pause in awe of the destructive power of wildland fires. Authorities note that we may anticipate growing numbers of people becoming affected by wildfire smoke in years to come because of the prevalence of wildfires. For example, there is an increasing trend of longer fire seasons in California, which means wildfires burn longer and consequently produce smoke longer.
What’s in wildfire smoke?
Before we talk about how to protect yourself from wildfire smoke, let’s first discuss what makes up the noxious clouds created by burning trees and grasses:
- Water vapor
- Carbon monoxide
- Ash and fine particles
- Other air pollutant chemicals
A number of these components in wildfire smoke are harmful to breathe in large amounts. A system often used to quantify these levels is called the Air Quality Index (AQI). The AQI assigns a numerical value to the harmful substances divided into six categories ranging from “Hazardous” to “Good.” The substances of greatest threat to human health are ozone, carbon monoxide, and fine airborne particles. The component of the highest concentration determines the AQI score.
The middle range, called “Unhealthy” with an AQI score of 151–200, is the starting point at which even healthy individuals may be harmed by inhaling wildfire smoke. Those with lung disease or other high-risk conditions will be affected at even lower AQI ranges. An individual’s health status ultimately determines the maximum AQI score that they can tolerate without negative effects.
What are the effects of wildfire smoke inhalation?
Wildfire smoke can be harmful for anyone. Short-term effects of smoke inhalation include:
- Throat irritation
- Chest pain
- Eye irritation
These symptoms generally resolve after moving to an area with cleaner air; however, there are some reports of long-term damage from wildfire smoke exposure. Fine airborne particles in smoke are an especially troublesome health risk. These particles have been shown to cause chronic lung inflammation in cases where the body’s natural defenses do not appropriately expel them by cough or phlegm production. Chronic inflammation in the lungs can cause a cascade of inflammation involving other organs of the body as well. Some particles are so small that they may cross from the lungs and go into the bloodstream.
Wildfire smoke can worsen symptoms in people with conditions like heart disease, asthma, and COPD. Also, young people, older adults, people with diabetes, and pregnant women are at higher risk for negative effects from wildfire smoke. High-risk individuals must be extremely cautious when living in an area affected by wildfire smoke.
How do I decrease my risk of wildfire smoke exposure?
If you are living or working in an area where there is wildfire smoke, here are some things you can do to decrease your health risk:
- Stay indoors and keep windows and doors closed.
- Keep indoor air as clean as possible by not adding fine particles to it (for example, do not smoke, burn candles, fry food, use a gas stove, or vacuum without a HEPA filter).
- Wear a well-fitted N95 mask if you will be outdoors for prolonged periods.
- If you are at high risk for negative effects from wildfire smoke, consider relocating to an area that is not impacted by wildfires/wildfire smoke (keep in mind wildfire smoke can spread over large geographic areas).
Finally, you may consider increasing filtration power in your home or workplace. Indoor filtration can be accomplished in several different ways. If you have a central heating and cooling system, you can use a high-efficiency filter, and keep the ventilation system continuously running so these filters are able to work. Portable home air purifiers using certified HEPA filters have also shown benefit in decreasing fine particles indoors.
If your current location isn’t safe because of nearby wildfires or because the weather makes it too hot in your home and you do not have air conditioning with appropriate filtration, stay elsewhere with family or friends or at a cleaner air public shelter until the threat clears.
What about ventilating indoors with outside air to decrease the risk of spreading COVID-19?
On a “Good” AQI day, opening windows and doors is a great way to ventilate the indoors with fresh outside air, and doing so may help decrease the risk of spreading COVID-19. However, when wildfire smoke is a hazard, creating a “clean room” with indoor air filtration may be a compromise between the current novel coronavirus pandemic and using outdoor air for ventilation. See the Environmental Protection Agency’s steps on creating a clean room to protect indoor air quality during a wildfire.
Speak with your primary care provider if you are concerned about wildfire smoke and your health.
AirNow.gov, “AQI Basics.”
AirNow.gov, “Fires and Your Health.”
AirNow.gov, “How Smoke from Fires Can Affect Your Health,” January 2017.
CalFire, “2020 Incident Archive.”
Carlyn J. Matz, Marika Egyed, Guoliang Xi, et al., “Health impact analysis of PM2.5 from wildfire smoke in Canada (2013–2015, 2017–2018), Science of the Total Environment 725,” (2020).
Eiji Tamagawa, Ni Bai, Kiyoshi Morimoto, et al., “Particulate matter exposure induces persistent lung inflammation and endothelial dysfunction,” American Journal of Physiology 295, no. 1 (2008).
Nancy Averett, “Smoke Signals: Teasing Out Adverse Health Effects of Wildfire Emissions,” Environmental Health Perspectives 124, no. 9 (2016).
Sarah B. Henderson, “The COVID-19 Pandemic and Wildfire Smoke: Potentially Concomitant Disasters,” American Journal of Public Health 110, no. 8.
United States Environmental Protection Agency, “COVID-19, Wildfires, and Indoor Air Quality.”
Virpi Kollanus, Marje Prank, Alexandra Gens, et al., “Mortality due to Vegetation Fire–Originated PM2.5 Exposure in Europe—Assessment for the Years 2005 and 2008,” Environmental Health Perspectives 125, no. 1 (2017).