Updated on November 18, 2024.
Wildfire season in North America typically runs from June to August. But in recent years, as climate change has caused hot, dry months to stretch into September, October, and even November, there have been an increasing number of fires in the fall season. That means that wildfire safety precautions are important almost year-round.
Wildfire smoke can also travel thousands of miles from its original source. Even if you live on the opposite side of the country from the source of a fire—or even in a different country entirely—your community can still be affected.
No matter where you live or the time of year, it’s important to understand the risks of wildfires. The good news is that there are science-backed ways to protect yourself and loved ones from the dangers of wildfire smoke exposure.
What makes wildfire smoke different
Wildfire smoke is different from the smoke you might get from a campfire, says toxicologist Christopher Weis, PhD, DABT, science director and principal at Weis Toxicology, LLC, a firm that specializes in identifying environmental hazards and mitigating risks and liabilities. That’s because fires often occur in the wildland urban interface (WUI), the area where the natural environment meets urban terrain. In these types of fires, wood is not the only substance that burns.
“If you look around your home, you’re probably going to find a lot of plastic,” Weis explains. When synthetic (human-made) building materials like insulation, vinyl flooring, and other plastics burn, they can emit potentially hazardous fumes, particles, and volatile chemicals.
The increased use of synthetic chemical materials in buildings and furniture has resulted in houses that burn faster and generate unique mixtures of toxic smoke. These emissions from WUI fires often contain known cancer-causing and endocrine-disrupting chemicals. (Endocrine disruptors, also known as hormone disrupters, change how hormones work in the body. Hormone changes could potentially lead to serious health issues over time, including certain cancers.)
When a wildfire burns at the wildland urban interface, it is difficult to protect everything in its path. “Burning homes, garages, and other man-made structures at the WUI all release fumes, aerosols, and particles that pose a threat to firefighters and residents, both nearby and many miles away from the fire,” Weis explains.
Health risks and wildfire smoke
Wildfire smoke can release many harmful pollutants into the air. These materials can include:
- Carbon monoxide, a colorless, odorless, and dangerous gas
- Heavy metals (potentially toxic metallic elements), including lead
- Formaldehyde, a cancer-causing chemical commonly used to embalm dead bodies, among other uses
- Volatile and semi volatile chemicals released from plastics and other synthetics
- Fumes and gasses that may linger in the air or in homes for days or months following a WUI fire
One component of wildfire smoke that’s of special concern is fine particulate matter, also known as PM2.5 because it is 2.5 microns in size or less. To picture how tiny these particles are, a single strand of hair is 30 times wider than a single PM2.5 particle.
"PM2.5 are dangerous particles,” says Weis. “Due to their small size, they can get deep into your lungs. From there, they can travel through the bloodstream and into the nervous system.”
PM2.5 and other pollutants from wildfire smoke can contribute to a range of health issues affecting several parts of the body. These include:
Lung health risks from wildfires
The level of lung health risk from wildfire smoke depends on how heavy the smoke is and the length of time it lingers after the fire. The concern with short-term exposure is irritation of the mouth, nose, and lungs. These symptoms usually subside quickly for most people who inhale small amounts of polluted air. For some people, like those with asthma or chemical sensitivities (allergy-like reactions to certain chemicals), exposure could have longer-lasting effects.
“Long-term exposure is known to be a serious problem because in adults and children it can cause inflammation in the lungs and lead to breathing problems,” Weis says.
Prolonged exposure to wildfire smoke can worsen existing lung conditions such as asthma and chronic obstructive pulmonary disease (COPD). That means people with these conditions are at a higher health risk during and after wildfires. Some studies also show a link between wildfire smoke and the formation of blood clots in the lungs (called pulmonary embolism), which can be life-threatening.
“It’s important to remember the specific effects on kids,” Weis adds. “Kids are not just little adults. They’re more likely to be affected by exposures from their environment, particularly exposure from breathing in pollutants.”
Heart health risks from wildfires
Wildfire smoke may also contribute to heart issues including heart attacks, heart disease, and heart failure.
“Smoke exposure is known to increase the rate of heart attacks in communities that are heavily affected,” says Weis. Exposure to wildfire smoke can be especially dangerous for people with heart disease.
Heart rhythm issues are another concern. A 2022 study published in the Journal of the American Heart Association found that breathing fine particulate matter contributed to irregular heart rhythms in teenagers. Untreated heart rhythm issues may contribute to stroke, heart failure, or cardiac arrest.
Brain health risks from wildfires
PM2.5 particles are so tiny that they can enter the brain either through the nose or through the bloodstream, leading to a range of brain health issues. “It can enter the central nervous system and affect cognitive function,” says Weis.
For example, one 2023 study published in JAMA Internal Medicine looked at the effect of PM2.5 exposure over time on nearly 28,000 U.S. adults older than 50 years. The researchers found that greater exposure to PM2.5 was linked with higher rates of dementia. The connection was strongest when exposure to fine particles came from agriculture and wildfires.
Cancer risks from wildfires
For people with frequent or long-term exposure, wildfire smoke can increase the risk of certain cancers, as well. Firefighters may be at particularly increased risk. Certain products that firefighters use to put out fires—and even some types of firefighting equipment—contain known cancer-causing chemicals called PFAS (per- and polyfluoroalkyl substances).
For example, the foam used to extinguish flames often contains a particular PFAS that is associated with kidney and testicular cancer. The protective gear that firefighters wear, known as turnout gear, may also contain chemicals that release PFAS. This increases their job-related health risks even further.
What’s more, the hazardous chemicals firefighters are exposed to are linked to reproductive health issues. These include preterm birth and miscarriage. In fact, as many as 22 percent of firefighter pregnancies end in miscarriage, according to a 2021 study published in Environmental Health. Despite these facts, there are scarce recommendations for women firefighters on when to stop working when pregnant or breastfeeding.
Some communities are at higher risk
Some people are more sensitive to the effects of wildfire smoke exposure than others. Factors that can increase long- and short-term risk include age and life phase, where you live, and where you work.
Your age and life phase
Pregnant people, children, and older adults are at a higher risk of being affected by wildfire smoke. These groups are more likely to have health effects from smoke exposure because their organs and body systems are more sensitive to pollutants.
Where you live
Neighborhood and housing type can potentially increase the risk of smoke exposure. For instance, in addition to potentially relying heavily on synthetic construction materials, affordable housing often lacks good insulation or ventilation. That means smoke can more easily enter buildings and can be harder to remove.
Communities with less access to healthcare services may also experience worse health outcomes after a wildfire. That’s because people may not be able to find a hospital or clinic when they need one or because those facilities may become overcrowded with limited supplies. If you or a loved one is concerned about local access to care, contact your local department of public health for help finding low- or no-cost health services.
Where you work
Outdoor workers don’t always have the luxury of staying inside on days with poor outdoor air quality. Some employers care more about how fast a project can be completed than their workers’ health and safety. California, Oregon, and Washington are currently the only states with laws protecting employees from wildfire smoke exposure.
Increased health risks in women firefighters
Firefighting is a traditionally male-dominated field and women make up a smaller percentage of the workforce. As a result, they have largely been left out of consideration when it comes to policies and practices. For example, the turnout gear that firefighters wear wasn’t designed for female bodies, which may lead to improper fit and less protection from harmful exposures.
People of color are disproportionately affected
People of color may be disproportionately affected by wildfire smoke exposure due to a combination of historical, social, and economic factors.
Communities with a history of segregation, for example, are more likely to be located near highways, toxic waste sites, industrial areas, and other areas with environmental and health risks. These areas may contain more synthetic building materials than other locations and may not have the proper planning to protect residents from wildfire damage or smoke. In addition, system-level inequalities in housing policies means that many communities of color have limited access to healthcare services.
The physical and mental stress of exposure to wildfire smoke, combined with chronic stress from the lived experience of discrimination, can make existing health issues in these communities worse.
How to protect yourself and loved ones
Given the health hazards associated with wildfire smoke exposure, it’s important to take steps to protect yourself and loved ones. The following guidance can help you reduce exposure risk and safeguard health in the event of a wildfire.
Check your community’s air quality index
Air quality is a measure of how clean or polluted the air is. The air quality index (AQI) is a scale from 0 to 500, designed to help you understand and weigh the risks of going outside on certain days. An AQI value of 50 or below indicates good air quality, while an AQI above 100 means members of sensitive groups, like pregnant people and people with asthma, should aim to stay indoors if possible.
Visit AirNow.gov from the Environmental Protection Agency (EPA) or download the AirNow smartphone app to check the air quality in your area and to learn about the location and risk posed by wildfires.
Shelter in place, if possible, when pollution levels are high
Local AQI readings above 151 may cause health issues for members of the general public and particularly for people with respiratory issues like asthma or COPD. The best course is to shelter in place if you can. Close your windows, doors, and anything else that connects to the outside, like vents and fireplace flues. If you have a mechanical heating, ventilation, and air conditioning (HVAC) system, run the air in “recirculation” mode. This will help prevent outside pollutants from entering your home.
If you have a child or an older loved one, aim to minimize their time outside. If school is still open, contact the office and request that kids play indoors until air quality improves. Children with asthma are legally permitted under the Americans with Disabilities Act (ADA) to skip outdoor sports and activities when their breathing is at risk.
If you need to go outside, wear the right mask
Not everyone has the option to stay indoors. Outdoor workers, for example, may risk losing their source of income if they stay home when their employer expects them to work.
If you have to leave home when pollution levels are high, wear an N95 mask. These are designed to filter out small particles, including PM2.5. They can be found at many retail and hardware stores and pharmacies. The Centers for Disease Control and Prevention (CDC) offers tips on how to properly wear an N95 mask.
Protect your indoor air quality
Having an effective air filtration system in your home can help keep smoke particles and other pollutants out. If you have an HVAC system, make sure it is regularly maintained and has a filter to remove particles. If possible, install a MERV filter of the highest rating possible. Replace the filter when it becomes dirty.
If you don’t have an HVAC system or if it doesn’t run properly, consider using a portable air purifier. The cost of a reliable portable air purifier can range from $100 to $300 at big retail stores and online. If you’re not sure how to choose the right air purifier for your space, refer to this expert-approved indoor air guide.
If you can’t afford a store-bought product or if it’s out of stock, you can make an air purifier at home using products available for low cost at most hardware or home improvement stores. Or follow these tips from the CDC to build your own air purifier.
Clean surfaces regularly
It’s important to clean after a wildfire to avoid buildup of dust or ash that could contain harmful residues from smoke. For hard surfaces like countertops, windowsills, furniture, and blinds, use a microfiber duster or a damp cloth to remove dust. Microfiber and damp cloths work by collecting the dust and trapping it. By contrast, traditional dry dusting tends to disperse dust into the air. Get more tips on how to effectively clean your home.
Have a “go bag”
Use the WUI Fire Property Awareness Explorer tool from the U.S. Fire Administration to help determine if your residence may be at risk from wildfires. If you live in a fire hazard zone, it can relieve some stress to be prepared to evacuate in advance.
Weis recommends packing a bag or two with any essentials you may need, such as drinking water, non-perishable foods, medications, and personal care items. Use a go-bag checklist when packing to make sure you have everything you’ll need.
“One of the most important things to have in your ‘go bag’ is an old-fashioned radio that works on batteries,” Weis says. “You need to have a way to listen for recommendations from local authorities outside of the internet and your cell phone because those services can be destroyed in a fire."
After a fire, don’t go home right away
Evacuating your home to avoid a wildfire can be a traumatic experience. “There’s a very natural tendency after an event like that to want to return to your home, to process what has just happened to you, and to see what you can salvage,” says Weis. “But with respect to fires, especially WUI fires, the fumes and smoke are extremely dangerous.”
If your home is affected by a fire, do not return until local emergency response officials tell you it is okay. Firefighters need to extinguish any smoldering fires and check for any potential sources of explosions, such as propane tanks for grilling.
Follow expert guidance
The Chemical Insights Research Institute (CIRI) has created a website to share free educational resources for protecting communities from wildfire smoke. The resource offers strategies to safeguard yourself and loved ones before, during, and after a wildfire.
This article has been written in collaboration with the Center for Children’s Health Assessment, Research Translation, and Combating Environmental Racism (CHARTER) at Emory University and the Chemical Insights Research Institute (CIRI) of UL Research Institutes, a leading independent safety science organization. CIRI is a nonprofit organization dedicated to researching the ways in which environmental exposures can affect human health and developing strategies for reducing health risks. CIRI provides data and resources to help educators, healthcare providers, and consumers make informed decisions to protect and improve the health of people everywhere. Marilyn Black, PhD, is Vice President and Senior Technical Advisor of CIRI.
