Every year, wildfire smoke seems to affect our air quality more and more. Where it once was mainly a problem for people who lived in certain areas, the increase in frequency and severity of wildfire smoke events have made this issue a nationwide threat. Traditionally, Alaska, the West and the Northwest experienced the most days affected by wildfire smoke, ranging from 90 to 111 days part of the U.S. now experiences at least 16 days of smoke per year.
“We are seeing an increase in mega fires,” Erika Moseson, MD, an ICU doctor and wildfire expert, explained. “The volume of the smoke caused by the duration and intensity of these fires can really generate large volumes of particulate matter that can travel for very long distances.”
This was made incredibly clear in June 2023, when 75 million people in the U.S. experienced unhealthy and hazardous air quality caused by smoke from Canada. The Lung Association’s State of the Air Report found that this blanket of smoke from Canadian wildfires drove levels of ozone and particle pollution higher in dozens of central and eastern states. People as far as Florida and Central Europe experienced the effects of these fires, made obvious by smoke hanging in the air. “That's why we've started to recognize that no one's immune from the potential health impacts of wildfire smoke,” Dr. Moseson continued.
The Dangerous Makeup of Wildfire Smoke
Many people don’t realize that wildfire smoke is a complicated mixture of a variety of pollutants including carbon monoxide, nitrogen oxides, VOCs and particulate matter (PM2.5). Most experts focus on the dangerous effects of PM2.5 because it is the primary pollutant, and the health effects are well documented. Particle pollution is so harmful to health that even low levels of fine particle exposure can be harmful. This is especially troubling for high-risk groups like children, older adults, people with lung or cardiovascular disease and during pregnancy.
But Dr. Moseson notes that the dangers hiding in wildfire smoke are more varied than in the past. “Most people think of forests burning, but now we are also seeing large areas that get completely consumed including towns, cities, gas stations, cars, etc. This is creating highly toxic smoke that includes PM2.5, which is the biggest threat, but also other toxins that may not be as well characterized, depending on what is actually burning,” she explained.
More recently, researchers are recognizing that wildfire smoke changes over time, affected by outside sources that intermingle with it while it hangs in the air. “As smoke travels through the air and is exposed to sunlight and other chemical reactions, it changes. We are still learning how the potential health impacts of wildfire smoke farther away may differ from the impacts from up close exposure,” Dr. Moseson continued.
How Climate Change Is Making Wildfires Worse
But what is fueling these megafires? Experts agree that, while it isn't the only factor, human-caused climate change is the main culprit. The changing climate has caused longer, drier and hotter summers. Besides affecting the amount of rain, warmer temperatures mean an increase in water evaporation from soil and leaves.
In the winter, less snowfall and earlier melting of snow is decreasing the overall snowpack every year. Warmer, milder winters allow insects and pathogens to survive regions that were once too cold for them. So, there is an increased number of infected, rotting or dry plants. This, along with the historical fire suppression policies in the U.S. have led to a dangerous buildup of "fuels” such as dead plants, grasses, leaf litter, sticks and trees. These are ideal conditions for extreme fires.
Staying Safe When Everyone Is at Risk
As an ICU doctor, Dr. Moseson sees first-hand how wildfire smoke affects the health of people in her community during and after a major smoke event. “What we see after a big wildfire event is an increase in the rate of cardiac death, which is obviously very scary. We also see an increased need for rescue medicine for people with lung disease, and an increased need for people to visit their doctor in general because of some unexplained symptoms,” she said. “People are having more COPD or asthma flare-ups and are going to the ER more which is concerning for all of us.”
Because of the extensive health risks of inhaling wildfire smoke, it is important to monitor when it is affecting your area. You can do this by consulting the air quality index (AQI) which indicates how bad air quality is on a scale from 1-500 (with 1 being the best air quality and 500 being the worst). An AQI over 300 is considered hazardous to everyone and means that you should stay indoors with the doors and windows closed as much as possible. In these instances, it may be a good idea to create a clean room which is a designated area in your house where the air is particularly protected. “One of the simplest things people can do is to get a HEPA filter and run it,” Dr. Moseson said.
When the air quality is between 50 and 300, Dr. Moseson recommends assessing the vulnerability of everyone in your household before deciding whether it is ok to go outdoors. “People who are most vulnerable to poor air quality tend to be young or elderly. The elderly because they often have other comorbidities and the young because they breathe in more air than adults,” she said. Individuals who are pregnant also face serious risks from wildfire smoke.
If you do decide to venture outside, N-95 masks can filter harmful particles, but they need to be properly fitted. Also refrain from high exertion activities, as heavy breathing means you are more likely to inhale unhealthy levels of smoke. Lastly, always watch for symptoms like wheezing or shortness of breath and contact your doctor if you experience new or worsening symptoms.
Learn more about preparing for wildfires at lung.org/wildfires.
Blog last updated: July 9, 2026
