Summer brings warm weather and with it comes wildfire season. Larger wildfires have become more common in the last decade, and their smoke can irritate the lungs. Can wildfire smoke cause cancer? Doctors don’t fully know the answer to this question yet. This article will explore the growing risk of wildfire smoke, what we know about how it increases lung health risks, and what you can do to protect yourself.

Increases in Wildfires Worldwide

Climate change and changing global temperatures have resulted in increased temperatures during the summer. These higher temperatures worldwide and the resulting dry conditions have led to larger forest fires and longer wildfire seasons.

Some of the world’s largest wildfires have happened in the last five years. Wildfire smoke can travel hundreds of miles and affect air quality there. Notably, Canadian fires in the summer of 2023 spread to New York City and other parts of the United States, making the air quality hazardous.

Due to the increase in large wildfires, there are more chances of coming into contact with wildfire smoke. This smoke can cause health problems, especially for people with respiratory (breathing) issues.

Wildfire Smoke: What’s in It?

Wildfires burn material around them. This burning of material releases smoke into the atmosphere, which contains different gases and small particulate matter. The smoke and particulates can change based on what the fire is burning. In general, wildfire smoke contains carbon monoxide and nitric oxide, which are gases.

Because wildfires can burn anything in their path, they may also contain carcinogens — cancer-causing chemicals. These can include:

• Asbestos
• Benzenes
• Formaldehyde
• Hydrocarbons
• Heavy metals

Fires break down substances into tiny particles and release them into the air. Most particles are either coarse or fine. Coarse particles are particles that are greater than 0.0001 inch (2.5 microns) but less than 10 microns in diameter. Fine particles have a diameter of less than 2.5 microns, also referred to as PM2.5. Coarse particles include pollen and mold. They can be stirred up into the air by agricultural machines and cars but also sometimes from wildfire smoke. Fine particles, which can be made from combusted materials and metals, are more common during wildfires.

The Environmental Protection Agency (EPA) puts out an index that describes how much air pollution there is on a given day. This is called the air quality index (AQI). The higher the AQI, the worse the air quality is. The index ranges from 0 to 500. High AQIs from wildfire smoke are usually caused by high amounts of fine particles.

Wildfire Smoke and Health Hazards

Both coarse and fine particles can pose a health risk. Coarse particles irritate the eyes, nose, and airways.

Fine particles, on the other hand, are more dangerous because they can be absorbed into your lungs and bloodstream. Absorbed fine particles in the bloodstream can cause bronchitis and make asthma symptoms worse. Breathing in fine particles has been linked to an increase in many health problems, including lung cancer.

Inflammation

When fine particles are absorbed into the bloodstream, they can activate the immune system and cause inflammation. One study from the University of California, Davis, compared blood samples from people who were exposed to wildfire smoke to their blood once the air quality improved. The researchers found that during the exposure to wildfire smoke, the blood samples had higher levels of inflammatory markers and certain types of immune cells.

Risk of Wildfire Smoke in People With and Without Lung Cancer

There is still a lot to learn about the relationship between wildfire smoke and lung cancer. Scientists are continuing to study how exposure to wildfire smoke affects long-term health.

Studies on Wildfire Smoke and Cancer

There haven’t been many studies on wildfire smoke and cancer risk. One study looked at rates of lung cancer in Canada in people who lived within a 31-mile (50-kilometer) distance from a forest fire compared to people who lived greater than 31 miles from a forest fire. Over 10 years, people who lived near the forest fires had a higher risk of developing lung cancer.

Another study looked at cancer risk from hazardous air pollutants in smoke in the western United States. They found that the risk of cancer after exposure was 10 in 1 million people compared to 0.71 in 1 million in the general U.S. population. This study was not specific to lung cancer.

Firefighters May Have an Increased Risk of Developing Lung Cancer

One way we know about the effects of wildfire smoke is through firefighters because they have more exposure to wildfire smoke than the average person. One study estimated that firefighters have between an 8 percent and 43 percent increased risk of developing lung cancer based on their overall exposure. Firefighters who had long-term exposures were at increased risk.

Risk for Those With Lung Cancer

If you already have lung cancer, is wildfire smoke going to affect your health negatively?

One study from 2022 tried to answer this question. The researchers looked at people with non-small cell lung cancer who were exposed to wildfire smoke after their discharge from the hospital. People who were exposed to wildfire smoke were less likely to survive than those who had not. The earlier they were exposed to smoke after being discharged, the lower their survival rate was.

What We Don’t Understand About Wildfire Smoke and Cancer

We still don’t know a lot about whether wildfire smoke can cause lung cancer. Not many studies have directly asked this question.

We don’t know how much smoke or how long you need to be exposed to smoke to increase your risk. However, if you have lung cancer, you are probably at a higher risk for hazards associated with wildfire smoke. It’s best to be cautious, although not all of these questions have been fully answered.

How To Protect Yourself Around Wildfire Smoke

It’s important to protect yourself when you’re in an area with wildfire smoke. Here are some tips to help you avoid the smoke:

1. Stay inside as much as possible with the air conditioner turned on.
2. Keep an air purifier in the room that you’re spending time in. This will clean the air around you.
3. Use a high-efficiency particulate air (HEPA) filter.
4. Wear an N95 respirator when outside. These masks keep out most particulates from the air.
5. Clean the filter in your air conditioner. A dirty filter can introduce more hazardous air quality.
6. Keep away from indoor spaces where people are smoking inside.
7. Limit the use of the stove or oven, as these appliances can release gases and strain the air filtration system, causing it to work harder or clog faster.
8. Avoid frequent vacuuming. Vacuuming can bring more particles into the air and make respiratory symptoms worse.
9. Make an evacuation plan. If the smoke is too bad in your area and your home isn’t providing clean air, plan to stay with a family member or friend in a place with better air quality.

Find Your Team

MyLungCancerTeam is the social network for people with lung cancer. On MyLungCancerTeam, more than 13,000 members come together to ask questions, give advice, and share their stories with others who understand life with lung cancer.

Are you living with lung cancer and wondering how wildfire smoke can affect your lung cancer risk? Share your experience in the comments below, or start a conversation by posting on your Activities page.