Can Wildfires Increase Your Risk of Lung Cancer?

Millions of people around the world have to breathe air contaminated with wildfire smoke. Here's how it affects your body and lung cancer risk.

Understanding wildfires

In 2020, there has been the Covid-19 pandemic, the social justice movement, the presidential election … and massive wildfires. They first made headlines in Australia in January, then the Siberian Tundra and the Amazon, and later the western United States. Wildfires have ravaged many parts of the globe on an unprecedented scale. As of Oct. 1, 2020, more than 44,000 wildfires have burned about 7.7 million acres this year in the United States alone, according to the Federation of American Scientists.

This is bad for the Earth and the people and animals who live on it—particularly those who breathe in the wildfire smoke, says Anthony Gerber, MD, a pulmonologist and professor of pulmonary, critical care, and sleep medicine at National Jewish Health and an associate professor of medicine at the University of Colorado Denver.

“Breathing wildfire smoke can have real short- and long-term health consequences,” he says, adding that the research in this field is still emerging.

wildfireRuslan Lusi / EyeEm/Getty Images

Why wildfires happen

You can expect more of the same in the future, says Noah Diffenbaugh, a professor at Stanford University’s School of Earth, Energy & Environmental Sciences and lead author of a paper examining the causes for the drastic increase in California’s wildfires. Many factors influence wildfire risk, but Diffenbaugh found that long-term warming due to global climate change, combined with decreasing autumn precipitation, is increasing the odds of these kinds of extreme weather conditions occurring.

“Bottom line is that this year wasn’t an aberration, this is the new normal, and people need to start planning for longer, hotter summers with more wildfires,” Dr. Gerber says. “Instead of arguing about it or ignoring it, we need to be talking about how to help people deal with it. All of us should be asking ourselves, ‘If the new normal is unhealthy air, what can I do to protect myself?'” (You can start by looking for these common air pollutants in your home)

Why breathing wildfire smoke is dangerous

Protecting yourself starts with understanding exactly why breathing wildfire smoke is harmful, says Jing Gennie Wang, MD, pulmonologist and assistant professor of pulmonary, critical care, and sleep medicine at The Ohio State University Wexner Medical Center.

Wildfire smoke is a type of air pollution and scientists define the extent of air pollution by measuring levels of toxic particulates. There are two main concerns with wildfire smoke, Dr. Wang says. First are the variety of toxic compounds based on what has been burned; for instance, you will find plastic, lead, heavy metals, and other toxins from burning buildings. Second are particulates. Larger particles of dust, dirt, and smoke can irritate eyes, skin, and throat but fine particles, those smaller than 2.5 μm in diameter, known as particulate matter (called PM2.5), are even more dangerous as they get deposited deep within the lungs and can even enter the bloodstream. (Here’s how you can cut down on indoor air pollution.)

The closer you are to the fires, the more of these pollutants you are exposed to. In Napa, California, scientists measured levels of PM2.5 nearly six times higher than the standard for air quality in the U.S. due to the nearby wildfire. Because the body has a hard time clearing fine particulates from your system, the effects can be cumulative over time. The more wildfire smoke you breathe, the worse the effects will be, she says. (Don’t forget about toxins in your water.)

How wildfires affect your health

Breathing wildfire smoke primarily harms your respiratory and cardiovascular systems, although the effects can cascade, causing issues in nearly every part of your body, Dr. Gerber says. Exposure to wildfire smoke affects the lungs and heart almost immediately, according to a June study published in Environmental Health Perspectives. This effect is especially pronounced in people who are already vulnerable like children, the elderly, smokers, and those with a pre-existing lung or cardiac condition, he says.

The long-term effects of breathing wildfire smoke are not well known but it has been shown that inhaling fine particulates causes oxidative stress, chronic inflammation, and cell toxicity, which can lead to serious health issues weeks, months, or even years later, Dr. Wang says. Long-term exposure to air pollution has also been linked to earlier death.

While breathing the smoke can cause long-term damage to your body, the more immediate danger is that it exacerbates existing conditions, Dr. Gerber says. “I can tell you from personal experience that we’ve seen an increase in patients at our clinics since the wildfire smoke has gotten bad in Denver. They come in for many different conditions but a lot of them will say that the smoke has made it worse,” he says. (Note: Breathing smoke from indoor fireplaces can also be harmful.)

man in field looking at wildfire smokeRobin Carleton / Aurora Photos/Getty Images


Wildfire smoke likely doesn’t cause asthma but it can make it a lot worse or cause a serious attack, Dr. Wang says. Inhaling fine particles causes irritation and lung inflammation.

Chronic obstructive pulmonary disease (COPD)

COPD is a chronic inflammatory lung disease that causes obstructed airflow from the lungs so sufferers already have compromised breathing. Adding smoke inhalation can make it an emergency situation, Dr. Wang says. “There is a documented increase in emergency room and outpatient visits as well as hospitalizations due to COPD that is exacerbated by breathing wildfire smoke,” she says.

Pulmonary infections

Exposure to wildfire smoke may also be associated with an increased risk of pulmonary infections, such as pneumonia and bronchitis, Dr. Wang says.

Heart attacks and strokes

“Many studies have found that breathing polluted air has detrimental effects on cardiovascular health, including increased hospitalizations for heart attacks, and ED visits for congestive heart failure exacerbations, and rates of out-of-hospital cardiac arrests,” Dr. Wang says.

Wildfires and Covid-19

An increased risk of infection from breathing wildfire smoke may also include Covid-19, Dr. Gerber says. While there aren’t any studies yet, damaged and irritated lungs are more vulnerable to infection in general and breathing smoke may make an existing infection more serious, he says.

People fleeing the wildfires may be forced to shelter in less-than-ideal situations that don’t allow for proper disinfection or social distancing, leading to Covid-19 exposure, he says. (This is what you need to know about coronavirus super spreading events.)

“Do know that while masks can help prevent the spread of Covid-19, most of the masks generally available won’t do anything to help with the smoke,” he adds. You should still wear your mask but take additional steps to protect yourself from the smoke.

Wildfire smoke and lung cancer risk

Meteorologists are fond of comparing wildfire smoke inhalation to cigarette smoking as a way to demonstrate the ongoing risk to the public in their forecasts. This is not really a good comparison, our doctors say. “For starters, cigarettes are addicting and no one is out there intentionally or habitually breathing wildfire smoke,” Dr. Gerber says.

Dr. Wang points out that the chemical composition of wildfire and cigarette smoke is very different, with wildfire smoke not containing the harmful tobacco and other cancer-causing toxins found in cigarettes.

That doesn’t mean you’re in the clear when it comes to lung cancer or other cancers. There is no definitive research yet but that may be because there are so many variables involved. “Your cancer risk really comes from what’s burning, how much smoke you’ve inhaled, and how long you’ve been exposed to it,” Dr. Gerber says. “I think we will learn a lot more about this in the coming years.”

How to understand the air quality in your area

The United States Environmental Protection Agency (EPA) uses the Air Quality Index (AQI) as a standardized tool for communicating daily air quality, which takes into account air pollutants measured within your specific area. The five major air pollutants that are measured are particulate matter, ozone, carbon monoxide, nitrogen dioxide, and sulfur dioxide. The AQI uses a color-coded scale—red, yellow, or green—to provide a description of the air quality and indicating the levels of concern and the health risks. You can find the daily AQI at AirNow but your local and state agency websites may have more accurate data for your location.

The AQI can be a useful tool for making general decisions, like whether or not to exercise outdoors, but shouldn’t be used to gauge health effects, Dr. Gerber says. “It’s a general guide based on population studies and loses effectiveness at an individual level,” he says. “Your personal risk will be affected by your health history, location, the time of day, the composition of smoke in your area, and the weather.”

Since knowing all of those factors is difficult, the best rule of thumb to go by is how you feel, he says. “You know your body best so if it feels bad, go back inside,” he says, adding that you should talk to your doctor about measures you can take to help your personal health conditions.

How to minimize your risk

You can’t stop breathing but there are some things that everyone can do to lower their risk of, and from, inhaling wildfire smoke. Precautions that our experts recommend include:

  • Minimize, limit, or strategically time your outdoor activities.

  • Keep windows and doors closed as much as possible and plug leaks.

  • Avoid the use of ventilation systems that allow outdoor air indoors, such as whole-house fans and certain air conditioning systems.

  • Use a high-efficiency particulate air filter indoors, like these air purifiers for smoke.

  • Avoid activities that generate indoor air pollution, such as smoking cigarettes, lighting candles, and cooking at high heat (frying, roasting, broiling, etc.).

Wearing an N95 or N100 respirator may offer some protection from inhalation of fine particles such as PM2.5, but not other toxic gases found in wildfire smoke, such as carbon monoxide.

Consult with your doctor as certain people with underlying respiratory or cardiovascular conditions at higher risk for complications due to wildfire smoke exposure should consider evacuation, Dr. Wang says.


Charlotte Hilton Andersen
Charlotte Hilton Andersen has been covering health and fitness for many major outlets, both in print and online, for 13 years. She's the author of two books, co-host of the Self Help Obsession podcast, and does freelance editing and ghostwriting. She teaches fitness classes in her spare time. She lives in Denver with her husband, four children, and three pets.