It isn’t just those in the path of the flames who are adversely affected by wildfires. With so many acres burning, wildfire smoke is becoming a significant human health concern. “We tend to think of wildfires in terms of direct exposure: Will my house burn?” says ecologist Tania Schoennagel. But wildfires also present a serious health hazard for the broader population, even those who reside thousands of miles away from the area burning. (Zaldal, 2010)
Although wildfires account for less than a quarter of all fine particulate patter (PM) emissions in the U.S., on those days when air quality exceeded regulatory standards, wildfires accounted for nearly 65% of PM 2.5 levels, suggesting wildfires play a significant role in pushing air quality out of compliance. Under the EPA’s Air Quality Index, a reading of 101-150 is considered unhealthy for sensitive groups. A 151 to 200 reading is unhealthy for everyone, and anything over 250 is considered very unhealthy. When wildfires are burning nearby, it’s common to get readings between 150 and 250 or even higher.
In the U.S. alone, smoke from wildfires leads to around 17,000 premature deaths each year, and this is projected to double by 2100 as wildfires grow worse with climate change. Just a few days of exposure to wildfire smoke can send people with asthma or other vulnerabilities to the E.R. “Even people who don’t have lung conditions have been feeling ill effects,” said one Washington resident as fires were burning in the state. “It’s like suddenly becoming a smoker,” adds another. (Carlton & Malas, 2018)
How far does wildfire smoke travel?
Most significant wildfires in the U.S occur in the arid west, in the region extending from the edge of the Rocky Mountains in Colorado to the west coast in states like California. Yet wildfire smoke doesn’t stay in those places. Jet streams can carry it eastward, impacting air quality hundreds or even thousands of miles away from where a forest fire is burning. The distance smoke travels depends on the size of the wildfire, weather patterns, and how high into the atmosphere the smoke plume reaches.
A study published in April 2022 in the journal +Nature Communications,+ authored by Rebecca Buchholz and her colleagues, found that fires in the Pacific Northwest “have the potential to impact surface air quality even at large distances downwind of the fires,” affecting people in Eastern states.
“In fact,” writes Megan Sever, “the majority of asthma-related deaths and emergency room visits attributed to fire smoke in the United States occur in eastern cities, according to a study in the September 2021 +GeoHealth.”+ (Sever, 2022) Wildfire smoke can be especially toxic to children living in cities, who are already exposed to more air pollution, which has weakened their respiratory and immune systems.
What’s in wildfire smoke?
All smoke contains what are referred to as PM 2.5 particles–fine particulate matter that’s no more than 2.5 micrometers wide, or roughly 1/30th the width of a human hair. These are particles small enough that they can get into the airway and even make their way into the blood to cause damage to the lungs, heart and brain. Wildfire smoke contains a lot of these worrisome particles.
When wildfires consume houses, power lines and other human-made structures, they burn material that releases all sorts of nasty chemicals into the atmosphere; toxins you definitely don’t want to be breathing. This can include everything from asbestos and arsenic to the array of harmful chemicals used in plastics.
Another thing few people realize is that wildfire smoke can contain airborne pathogens. Fire has the effect of aerosoling many species of fungi and bacteria that wouldn’t otherwise be airborne, releasing more microbes into the atmosphere. For example, air samples taken near wildfires in Utah found more than 100 different airborne fungi that weren’t in the air before the fire. Many of these are benign to humans, but they can also include pathogens like valley fever.
How harmful is wildfire smoke?
Experts used to think that wildfire smoke, which consists mostly of wood and vegetation, was less harmful than industrial pollution. Recent studies are casting doubt on that narrative, suggesting wildfire smoke may actually be more harmful than industrial pollution.
A study by atmospheric chemist Ga Lee Ng and his colleagues found that particulate matter from wildfire smoke can be more toxic than the urban kind, “inducing about five times higher cellular oxidative stress,” he says. It also seems to become more toxic as it travels through the atmosphere and reacts to sunlight and atmospheric gases, so over time, “the health effects per gram are greater,” according to Daniel Jaffe, an atmospheric chemist.
Wildfire smoke & its effects on children
Children, due to their age and physiology, are especially vulnerable to airborne pollutants such as wildfire smoke. First, they have higher respiratory rates, so they breathe more air per pound of body weight than adults, which translates into a higher dose of whatever contaminants are in the air. Smaller lungs mean more of their total lung surface is exposed. And because they are young and still developing, children’s organs can be more sensitive. Chemical exposure thus casts a broader shadow and leaves a longer legacy.
A study by environmental scientist Rosana Aguilera and her colleagues, published in +Pediatrics+ in 2021, analyzed pediatric respiratory-related ER and urgent care visits in San Diego County from 2011 to 2017. Her team found that wildfire-specific PM 2.5 was 10-times as harmful to respiratory health in children 5 and under as ambient pm 2.5.
Even a small increase in PM 2.5 by wildfires can increase respiratory-related ER and urgent care visits in kids under 12, according to an earlier 2020 study led by Aguilera in the +Annals of the American Thoracic Society. “Even relatively smaller wildfires can still generate quite an impact on the pediatric population,” she says.
Animal studies have been especially worrisome. A 2008 study looked at a group of infant rhesus macaques at the California National Primate Research center following a series of devastating wildfires in Northern California that year, comparing them with a group born a year later. By age 3, the smoke-exposed monkeys had reduced lung capacity, lung volume and lung function, along with higher rates of immune disorders. “Early life smoke exposure…changed the trajectory of lung development” in a way that doesn’t seem to be reversible, says molecular biologist Hong Ji, who wasn’t involved in the study.
Separate research on monkeys by Ji and her colleagues found exposure to wildfire smoke in infancy can lead to long-term changes in the nervous and immune system of monkeys. It also impacts brain development. Early exposure to wildfire smoke can even lead to DNA changes that are passed down from generation to generation. The more scientists study the issue, “the more dangerous we realize it is,” says Sever.
Parents shouldn’t panic at this information. Scientists often dramatize their findings, and the bitter truth is that your kids are being exposed to other chemicals on a daily basis that have been linked to similar adverse effects. (See our area on chemicals & toxins.) So it’s not as though your child is doomed if they catch a few whiffs of wildfire smoke. But it does mean you should take basic precautions to avoid unnecessary exposure. Tips to help you do this are included at the bottom of this page.
Asthma & wildfire smoke
Wildfire smoke tends to be especially detrimental on those who are asthmatic, since anything that aggravates the lungs will worsen asthma symptoms. Asthma is a widespread condition, affecting around 8% of adults and 7% of children, according to the CDC, or roughly 25 million Americans in total.
As wildfires worsen, so will problems with asthma. A study by environmental epidemiologist Jennifer Stowell and her colleagues, published in the Jan. 2022 +Environmental Research Letters,+ estimated that by the 2050s, wildfire smoke in the west will lead to an additional 155,000 asthma-related ER visits and hospitalizations every fire season just in the west alone.
True to what we discussed earlier, those in the east are affected too. A study by atmospheric scientist Katelyn O’Dell and her colleagues found that more people in the east visit the ER and are hospitalized with asthma-related problems from wildfire smoke than those west of the Rockies. Part of this is due to the fact that the east coast has a higher population (220 million people east of the Rockies compared to 64 million west of them), and part of it is due to the fact that dirtier air in big cities in the eastern United States has put people at a previous disadvantage. Over the 13-year study period (2006-2018), it was estimated 74% of asthma-related deaths and 75% of asthma ER visits and hospitalizations were provoked by smoke carried downwind from wildfires east of the Rockies, accounting for 4,600 of the 6,300 excess deaths from asthma.
Wildfire smoke & heart attack risk
Those with pre-existing heart conditions can be negatively impacted by wildfire smoke. It’s estimated that exposure to heavy smoke during the 2015-2017 wildfires in California raised the risk of heart attacks by up to 70%. (Sever, 2021)
Wildfire smoke & its effects on the brain
Air pollution can have profound effects on the brain, leading to impaired cognitive development. (See our information on air pollution.) Wildfire smoke is no exception. Small particles get into the bloodstream and find their way to the brain, where they can wreak havoc. Toxicologist Mathew Campen believes wildfire smoke PM 2.5 has a bigger effect on the brain than the lungs, leading to “profound” inflammation in the brain. Studies in mice found an inflammatory effect within 24 hours of exposure. But once again, duration of exposure is key to the equation: Breathing in wildfire smoke over the course of a week isn’t going to have as profound of an effect as breathing in air pollution from a city year round. But it certainly doesn’t help the situation.
Protecting your family from wildfire smoke
Here are some simple precautions you can take to limit your family’s exposure:
- Avoid outdoor activities on days when the air quality is bad, and keep kids inside.
- Close all windows.
- Turn on any air purifiers you might have.
- Purchase some indoor plants, which improve the air quality inside your home.
- Wear good masks when outside. N95 and KN95 masks will keep out harmful particles from wildfire smoke, as will virus masks.
References:
Gorney, C. (2021) “Where there’s fire, there’s toxic smoke,” National Geographic, April, pp. 60-67
Sever, M. (2022, June 18) “Wildfire smoke threatens health from afar,” Science News, pp. 17-21
See also…
- Fire Resistant Homes: Building or Retrofitting a House in Wildfire-Prone Areas
- Protecting Your Home From Wildfires: How To Reduce Wildfire Risk
- Wildfire Smoke & Its Effects on Human Health