LLast week, smoke from more than 100 wildfires across Canada rolled far away from the blazes into North American cities. New York City and Detroit were ranked among the five most polluted cities in the world due to the June 7 fires. The smoke has triggered air quality warnings in several states in recent weeks.
We asked Chris Migliaccio, a toxicologist at the University of Montana who studies the human health effects of wildfire smoke, about the health risks people may be exposed to when smoke wafts in from distant wildfires.
What is a problem in wildfire smoke?
When we talk about air quality, we often talk about PM2.5. This is particulate matter that is 2.5 microns in size or smaller – small enough that it can get deep into the lungs.
Exposure to PM2.5 from smoke or other air pollution, such as Emissions, such as vehicle emissions, can aggravate health conditions like asthma and affect lung function in ways that can exacerbate existing respiratory problems and even heart disease.
But the term PM2.5 only indicates size, not composition – what burns can make a significant difference in chemistry.
In the northern Rocky Mountains, where I live, most fires are fueled by vegetation, but not all vegetation is created equal. As the fire burns at the intersection of forest and city, manufactured fuels from homes and vehicles can also burn, and that too will create its own toxic chemistry. Chemists often speak of the potential of volatile organic compounds (VOCs), carbon monoxide and PAHs, or polycyclic aromatic hydrocarbons, produced when biomass and other materials are burned to harm human health.
How does inhaling wildfire smoke harm human health?
If you’ve ever stood by a campfire and had a puff of smoke in your face, you were probably irritable. Exposure to wildfire smoke can cause irritation of the nose and throat and possible inflammation. If you’re healthy, your body will mostly be able to handle it.
As with many things, the dose makes the poison—almost anything can be harmful above a certain dose.
In general, cells in the lungs called alveolar macrophages take up the particles and excrete them – in appropriate doses. When the system is overloaded, problems can arise.
One concern is that smoke can suppress macrophage function, altering it enough to make you more susceptible to respiratory infections. A colleague studying the lag time in the effect of smoke pollution from wildfires found an increase in influenza cases after a severe fire season. Studies in developing countries have also found an increase in respiratory infections among people who cook over open fires in their homes.
The stress of an inflammatory response can also make existing health problems worse. Exposure to wood smoke does not necessarily result in a heart attack, but if underlying risk factors are present, such as B. a heavy plaque build-up, the additional stress can increase the risk.
Researchers are also studying possible effects of inhaled fine dust particles on the brain and nervous system.
Does its toxicity change when smoke blows long distances?
We know that the chemistry of wildfire smoke is changing. The longer it stays in the atmosphere, the more the chemistry is altered by ultraviolet light, but we still have a lot to learn.
Researchers have found that the longer smoke is in the air, the higher the rate of oxidation appears to be, producing oxidants and free radicals. The specific health effects are not yet clear, but there is evidence that higher exposure leads to greater health effects.
It is believed that the longer smoke is exposed to UV light, the more free radicals are formed, increasing the risk of damage to health. Much of this, in turn, depends on the dosage.
If you are a healthy person, a bike ride or a hike in a light haze is probably not a big problem and your body can recover.
However, doing this every day for a month in the smoke of a wildfire is cause for concern. I worked on studies with residents of Seeley Lake, Montana who were exposed to dangerous levels of PM2.5 from wildfire smoke for 49 days in 2017. A year later we noticed a deterioration in lung function. No one was getting oxygen, but there was a significant drop.
This is a relatively new area of research and we still have a lot to learn, especially given the increased wildfire activity as the planet warms.
What precautions can people take to reduce risk from wildfire smoke?
If there is smoke in the air, you should reduce your exposure.
Can you avoid the smoke completely? Not unless you are in a hermetically sealed home. Unless you have a really good HVAC system, say with MERV 15 or better filters, there is little difference in PM levels indoors and outdoors. But when you go indoors, your activity decreases, so your breathing rate is slower and the amount of smoke you inhale is likely to be less.
In addition, if you belong to a vulnerable group, such as people with asthma, we recommend that you create a safe space at home and in the office with a high-level self-contained air filtration system to create a cleaner air space.
Some masks can help. There is no harm in having a quality N95 mask. However, just wearing a cloth mask doesn’t do much good.
Most states have air quality meters that can give you an idea of how bad the air quality is. Therefore, check these locations and act accordingly.
Christopher T. Migliaccio is a research associate in toxicology at the University of Montana
This article was republished by Conversation, a nonprofit news organization dedicated to sharing ideas from academic experts