Smoke from wildfires contains a complex mixture of gases, hazardous air pollutants, water vapor and particulate matter (or particulate pollution) that pose the greatest threat.
Some of these particles, including dust, dirt, soot or smoke, are so large or dark that they can be seen with the naked eye. But the smallest of these — microscopic particles that are about five to 30 times smaller than the width of a human hair — can travel deep into your lungs and even into your blood. There, they can cause inflammation and weaken your immune system.
While ash and soot from burning wood are some of the most worrisome types of particulate pollution, wildfire smoke can also contain other toxic and cancer-causing substances, including chemicals, heavy metals and plastics. Indeed, said Dr. John Balms, a pulmonologist and professor of medicine at the University of California, San Francisco: wildfire smoke is “pretty much like tobacco smoke without the nicotine.”
Inhaling wildfire smoke can make anyone cough, wheeze, and gasp for air. It can irritate the eyes, nose and throat and cause headaches.
People with certain illnesses such as asthma, chronic obstructive pulmonary disease or heart disease are particularly vulnerable, as are those who are very young, very old or pregnant. Even short-term exposures can have long-term consequences: A 2021 study conducted in California concluded that just one week of exposure to wildfire smoke was associated with a 3 percent increase in preterm births.
Lower-income areas and communities of color may also be at greater risk of health threats from wildfire smoke because they are more likely to breathe in daily pollution from cars, trucks and power plants, said Keith Bain, atmospheric scientist at the Air Quality Research Center at the University of California, Davis. “That leaves you behind when there’s a wildfire,” he said, adding that the simultaneous exposure to smoke and smog is an environmental justice issue that “adds insult to injury.”
If a wildfire is close enough that you can see flames, or if your community is covered in smoke and ash, you should be prepared to evacuate if instructed to do so, according to the Environmental Protection Agency.
Even if you’re far from the flames but smoke is obscuring your sky, your safest bet may be to evacuate, Dr. Prunicki said. If that’s not feasible, probably the next best thing is to stay indoors and take steps to limit your exposure to smoke.
According to the EPA, vulnerable people such as the elderly, children and people with heart or lung disease should avoid going outside when the air quality index — a number from 0 to 500 that indicates air pollution and health risk levels – goes over 100. Anything over 150 means it’s not healthy for anyone to be outside without a high-quality mask.
You can consult AirNow’s interactive fire and smoke map, a federally operated tool for tracking air quality conditions. PurpleAir can also offer a more local picture of air quality, as well as other products and applications, such as IQAir and BreezoMeter.
For children, safety concerns arise when the air quality index is even lower. Because smoke inhalation can increase the risk of asthma in children and can even have irreversible effects on their immune cells, experts recommend that when the air quality index is above 50, caregivers should start think about keeping children inside, especially if they already have asthma.
This is not always easy. Public health experts recognize that parents need to give children room to move. So one compromise “is for the child to wear a mask outside,” Dr. Balmes said. But keep in mind that dust masks, surgical masks and bandanas won’t be enough to protect your child from smoke, according to the Centers for Disease Control and Prevention. And higher-quality masks, such as N95s, are usually only available in adult sizes, so children may not be fully protected when wearing them. In all cases, outdoor play time should be limited.
By some estimates, a good air filtration system can reduce indoor smoke pollution by about 50 to 80 percent. When the skies turn foggy, if you have central air and heat, close your windows and switch your system’s filtration settings to recirculation. Adding a higher efficiency filter, such as one with at least a Minimum Efficiency Reporting Value (MERV) of 13, to central air systems makes them even more effective at removing small particles from smoke. If you don’t have central air, portable air purifiers with HEPA filters can work well in smaller spaces.
Experts warn that you should avoid using air purifiers that rely on and emit ozone, which can be harmful even at low levels and can irritate the lungs. Check with local community agencies to see if they provide guidance or financial support for purchasing air filters. People with low incomes and certain respiratory illnesses who live in the Bay Area, for example, are eligible for free portable air filters.
If you can’t find an affordable air purifier, you can make one from a box with a fan, some tape, and some high-efficiency filters.
Thick smoke can creep into your home through loose seals and cracks; closing them may help. Simply closing the windows can reduce pollution by about 30 percent. If it still smells like barbecue inside on a smoky day, placing wet towels around cracks under doors and around windows can slow smoke from entering your home.
The EPA also recommends avoiding activities like cooking, vacuuming, or smoking on smoky days that can stir up pollutants already in your home. And the American Lung Association recommends using a good welcome mat to wipe off your shoes, or taking them off completely when walking around your home to avoid trailing pollutants.
If your indoor space is larger than the air purifier can filter, the EPA recommends setting aside one room as a “clean room” to use as a refuge on smogier days. But avoid using rooms where you create smoke or other particles indoors, such as the kitchen or any room with lots of windows and doors.
Health experts say it can. Air pollution can cause stress and inflammation in your brain as it fights invading particles, according to Dr. Robin Cooper, associate clinical professor of psychiatry at the University of California, San Francisco. And it can compromise executive functioning, or the cognitive skills that help guide your choices, including working memory and self-control, she added.
“It interferes with your ability to think clearly,” Dr. Cooper said. “The headache is part of it.”
Direct exposure to wildfire can increase the risk of certain mental conditions, including post-traumatic stress disorder and depression. And there is some preliminary evidence to suggest that some people may also have increased anxiety, fear and stress during or after exposure.
Dr. Cooper, who has been in private practice for more than 40 years, said she has seen increased anxiety among her patients who have encountered wildfire smoke in the past. One Bay Area mother, she recalled, was so concerned about whether she would be able to protect her child from wildfire smoke that she worried she should never have become a parent in the first place.
But making sure you’re prepared for the dangers of wildfire smoke before a fire starts can help, Dr. Cooper said. This might include setting aside good N95 masks for smoky days, stocking up on supplies like bottled water, non-perishable food, personal care products and flash packs if you have to huddle indoors, or having a bag ready if you have to evacuate .
Not to mention, Dr. Cooper added, talking to your friends and neighbors about how you feel about climate change and how to prepare for the smoke when it comes. “Collective engagement with other people reduces feelings of isolation,” she said. “Builds resilience.”
Limiting time outside is a good start. There is no safe distance from the smoke and its health effects can be cumulative. So if you must go outdoors, wearing a high-quality mask, such as an N95 respirator, is essential.
Reporters at Wirecutter, a New York Times company that reviews and recommends products, suggest choosing a mask that filters exhaled air as well as inhaled air. You want to check that the mask has a good seal around your nose and mouth. Cloth masks are less effective.
And keep in mind that no mask will protect you 100 percent. “Wearing an N95 reduces your exposure, but if you have to go out, you’re going to be exposed,” Dr. Balmes said.
There’s also some evidence that you might want to protect your skin when you go outside. In a first-of-its-kind study published in 2021, researchers found links between short-term smoke exposure and health care visits for itchy skin and eczema.
Some creams and skin care products with labels like “anti-pollution” or “anti-pollution” probably won’t do much. Although applying a lotion with emollient properties – such as shea butter, lanolin or petroleum jelly – before going outside can help create an artificial barrier on your skin. Dermatologists advise avoiding smoking if you can, covering up with long sleeves and pants if you must go outside, and cleansing your skin after spending time outdoors to remove any pollutants.