How wildfire smoke can harm human health, even when the fire is hundreds of miles away – a toxicologist explains

Christopher T. Migliaccio, University of Montana

Smoke from more than 100 wildfires burning across Canada has been turning skies hazy in North American cities far from the flames. We asked Chris Migliaccio, a toxicologist at the University of Montana who studies the impact of wildfire smoke on human health, about the health risks people can face when smoke blows in from distant wildfires.

What’s in wildfire smoke that’s a problem?

When we talk about air quality, we often talk about PM2.5. That’s particulate matter 2.5 microns or smaller – small enough that it can travel deep into the lungs.

Exposure to PM2.5 from smoke or other air pollution, such as vehicle emissions, can exacerbate health conditions like asthma and reduce lung function in ways that can worsen existing respiratory problems and even heart disease.

But the term PM2.5 only tells you about size, not composition – what is burning can make a significant difference in the chemistry.

In the northern Rockies, where I live, most fires are fueled by vegetation, but not all vegetation is the same. If the fire is in the wildland urban interface, manufactured fuels from homes and vehicles may also be burning, and that’s going to create its own toxic chemistry, as well. Chemists often talk about volatile organic compounds, (VOCs), carbon monoxide and PAHs, or polycyclic aromatic hydrocarbons produced when biomass and other matter burns having the potential to harm human health.

How does inhaling wildfire smoke harm human health?

If you have ever been around a campfire and got a blast of smoke in your face, you probably had some irritation. With exposure to wildfire smoke, you might get some irritation in the nose and throat and maybe some inflammation. If you’re healthy, your body for the most part will be able to handle it.

As with a lot of things, the dose makes the poison – almost anything can be harmful at a certain dose.

Generally, cells in the lungs called alveolar macrophages will pick up the particulates and clear them out – at reasonable doses. It’s when the system gets overwhelmed that you can have a problem.

One concern is that smoke can suppress macrophage function, altering it enough that you become more susceptible to respiratory infection. A colleague who looked at lag time in the effect of wildfire smoke exposure found an increase in influenza cases after a bad fire season. Studies in developing countries have also found increases in respiratory infections with people who are cooking on open fires in homes.

The stress of an inflammatory response can also exacerbate existing health problems. Being exposed to wood smoke won’t independently cause someone to have a heart attack, but if they have underlying risk factors, such as significant plaque buildup, the added stress can increase the risk.

Researchers are also studying potential effects on the brain and nervous system from inhaled particulate matter.

When smoke blows over long distances, does its toxicity change?

We know that the chemistry of wildfire smoke changes. The longer it’s in the atmosphere, the more the chemistry will be altered by ultraviolet light, but we still have a lot to learn.

Researchers have found that there seems to be a higher level of oxidation, so oxidants and free radicals are being generated the longer smoke is in the air. The specific health effects aren’t yet clear, but there’s some indication that more exposure leads to greater health effects.

The supposition is that more free radicals are generated the longer smoke is exposed to UV light, so there’s a greater potential for health harm. A lot of that, again, comes down to dose.

Chances are, if you’re a healthy individual, going for a bike ride or a hike in light haze won’t be a big deal, and your body will be able to recover.

If you’re doing that every day for a month in wildfire smoke, however, that raises more concerns. I’ve worked on studies with residents at Seeley Lake in Montana who were exposed to hazardous levels of PM2.5 from wildfire smoke for 49 days in 2017. We found a decrease in lung function a year later. No one was on oxygen, but there was a significant drop.

This is a relatively new area of research, and there’s still a lot we’re learning, especially with the increase in wildfire activity as the planet warms.

What precautions can people take to reduce their risk from wildfire smoke?

If there is smoke in the air, you want to decrease your exposure.

Can you completely avoid the smoke? Not unless you’re in a hermetically sealed home. The PM levels aren’t much different indoors and out unless you have a really good HVAC system, such as those with MERV 15 or better filters. But going inside decreases your activity, so your breathing rate is slower and the amount of smoke you’re inhaling is likely lower.

We also tend to advise people that if you’re in a susceptible group, such as those with asthma, create a safe space at home and in the office with a high-level stand-alone air filtration system to create a space with cleaner air.

Some masks can help. It doesn’t hurt to have a high-quality N95 mask. Just wearing a cloth mask won’t do much, though.

Most states have air quality monitors that can give you a sense of how bad the air quality is, so check those sites and act accordingly.

This article was updated May 26, 2023, with over 100 fires now burning.

Christopher T. Migliaccio, Research Associate Professor in Toxicology, University of Montana

This article is republished from The Conversation under a Creative Commons license. Read the original article.

I didn’t see Thunderbolt and Lightfoot when it first came out – and later I spent several years working along the highline where it was filmed.  It showed up on youtube – free to view if you’re willing to put up with ads – and, with the familiarity with the area, and the fact that I was in my early 20’s when it was filmed, I enjoyed a Clint Eastwood movie that I hadn’t seen.

The movie starts with Clint preaching a sermon – only to be interrupted by a guy trying to shoot him with a broomhandle Mauser.

Dad had told a story about pre-revolution Chinese officials shooting out his tires with Brooms in China before I was born – I’m not sure the Marine sergeant that pulled him out of the jam wasn’t the source of my name “Michael.”  So it starts with a church I’ve seen, and Eastwood under fire from a gun I enjoyed rebuilding in the late eighties – until Bill Clinton froze my source of Chinese Broomhandles.  If I’m remembering correctly, the old church in Hobson was taken down in the eighties, and moved (either in part or total) to Troy – but memory is a fickle thing.

The cars – first Thunderbolt and Lightfoot liberate a 72 Buick Riviera.  Dad had one – the same tan color (the one pictured looks a lot nicer).  The guy who was trying to shoot Eastwood with the broomhandle was driving a 51 Mercury club coupe – in high school and college, I drove a 50.  Gerald Johnson gave me a transmission from his 51 when that engine blew.  I’d never realized that my car choices were so close to Eastwood’s.

While I was working in Chinook, I met a deputy whose Model 29 Smith had Eastwood’s autograph on the butt.  Not a bad thing, but he had added a bunch of clear sealant to protect the autograph, and couldn’t get the grips off when the bloody thing went out of time.  A Clint Eastwood autograph undoubtedly has value – but I really like having a firm belief that my revolver will be in time, and go bang, when I squeeze the trigger.

Then there was the gun that gave Clint’s character the name “Thunderbolt”.  So help me, a 20 mm Oerlikon.  The most produced anti aircraft cannon of World War II.  Responsible for almost half the Japanese aircraft shot down during the war.  Dad’s comment was that he got nervous when the 20 millimeters opened fire – those Japanese planes were too close to his ship.  Still, the Oerlikon was the late war Kamikaze killer.

Clint was using the Oerlikon to create an opening in the bank vault.  Now the Oerlikon is the only cannon I know of that fires from blowback – like a 22.  Like a Hi-Point.  I’m kind of accustomed to some sort of locked breech even in pistol calibers – but the Oerlikon firing pin hits the primer before that 50 pound breechblock even closes.  I mean, yes, it was the most common cannon in the US Fleet – but a 20 mm cannon just seems a little too much for blowback.

I’m pretty sure the schoolhouse where the loot was hidden is alongside the highway by Saco.  If you drive by on highway 2, look for it.  I liked the scenes in Fort Benton – the trees have grown since 1972, but it’s still identifiable.  Great Falls, over 50 years, has seen a lot of rebuilding.  Still, if you have spent time in central Montana and along the High Line, I hope you can enjoy the old movie as much as I.  I do wish that I had been able to watch it with Dad – and put the movie on pause to talk about everything we would have recognized.

It’s reached a point where 9mm ammunition is the cheapest centerfire cartridge available.  When I was younger, that title belonged to 38 Specials – but somewhere along the years, it moved to the old 9mm parabellum.  Back in the revolver day, it made sense (at least to me) to have a revolver and a lever action carbine in 357 magnum – where I could feed either with 38 specials or 357 magnums.  Now, as revolvers have given way to semiautomatic pistols, the default option is 9mm.

The chart shows the power advantage that a carbine has over a pistol – and the carbine makes hitting the target a bit easier.  The next chart  shows the differences between velocity based on barrel length for the 357 magnum. 

Since velocity correlates with power when the same bullet weights are used, that 16 inch barrel offers about 17% more energy than the 6-inch barrel on my revolver.  Going back to the 9mm, the carbine bounces the power up by about 46% over the pistol (and it’s worth mentioning that my 9mm pistol barrel isn’t quite 4 inches long).

A century and a half ago, the combination was in 44-40 – the Colt Frontier revolver and the Winchester model 1873.  That carbine showed the same 17% advantage as the 357 magnum charts – the bottom line is that the longer barrel offers more power and is easier to hit with.  The combination in the same caliber meant that the same box of ammunition could feed both rifle and revolver.

Occasionally, someone asks about the best pistol cartridge for bear country.  I’ve never had to deal with a bear attack.  I have had a fistfull of 22, of 38, of 357, and of 45 when I’ve been fairly close to a large grizzly – if you go back and click the link, you will quickly see that no handgun fills me with absolute confidence.  Despite that, it is easy to remember that Bella Twin used a single-shot 22 rifle, with 22 long (not even long rifle) cartridges to take the world record 1953 grizzly in Alberta.  This photo shows Bella Twin’s bear rifle:

Robert Ruark wrote the book Use Enough Gun.   The chart below suggest that a big part of using enough gun is having a long enough barrel.

At any rate, there is an argument to be made for pistol caliber carbines – whether in bear country or facing a paper target.  My own, from the pre-cataract surgery days, is a Hi-point 9mm with a simple red dot sight added.  It isn’t enough gun – but it beats praying.

My thoughts go back almost 35 years – to a time with a vertebrae smashed with a compression fracture, a brace that I wore constantly, and a 10 pound lifting limit. Fundamentally, the back part of the vertebrae had been converted to bone mush, and I was fortunate in having trained people calmly get me strapped to the backboard and hauled out.

After that, the medical part was just living in the brace, walking in my one pair of slip-on shoes, and doing nothing. As Fall moved into winter, I was visited by two old friends – Winton and Hallie Weydemeyer. I had known for years that Hallie was a Christian Scientist – but I had never expected to have Hallie show up to use the power of prayer to heal me.

With snow covering the ground, Renata abandoned me (after hiding my shoes) to Hallie’s prayers. Winton threw in a few (kind of like a relief pitcher) whenever Hallie would run down, and then she would return with new vigor to pray me better.

I don’t know whether the prayer was effective or not – the initial x-rays show a vertebrae that slopes down at about a 45 degree angle – not safe in any sort of a fall or strain. A future surgery to fuse things to better protect the spinal cord was a strong option. The post-prayer x-rays show a shorter vertebrae, still sloping, but at probably 5 or 6 degrees. It could be that the bone, turned into mush by the impact, just reformed as best it could as I spent the months of recovery in a brace, 24-7. It could be that Hallie and Winton got the divine intervention they requested.

And when people come to heal you with several hours of tag-team prayers, you really do have to be polite. After all, I don’t have any evidence that it hurts recovery.

I noticed this cartoon – and it holds a message that doesn’t come from the typical guidance counselor’s office:

It’s a slightly different way of displaying the bell curves that explain IQ (intelligence, the G factor)

The article describes parts of the author’s life after the brain injuries associated with multiple concussions – “Two standard deviations below the mean is considered to be low IQ or mentally handicapped. We accept that people with low IQ fall outside the norm and may need additional assistance to adapt and be successful in society. Sadly, the same compassion and understanding does not often exist for people more than two standard deviations above the mean.  The existence of only “positive” words to describe IQ on the high side is an example of that. A big difficulty for people with high IQs is that they are sorely in the minority.  Though there is a long tale to the bell curve it is a narrow one.  96% of all people fall within 30 points of the mean IQ of 100.”  Clicking the link takes you to her page, where she discusses her own experiences of high intelligence and traumatic brain injury.

“One of the biggest difficulties for Gifted/Brain Injured adults is that all of our life we have been able to rely on our ability to pick things up quickly, make the thought connections between disparate ideas, multitask, multi-think . . .  We relied on it even if we were unaware that we were doing so. Suddenly those abilities have been stripped from us.  That is huge. We are completely at a loss how to navigate life.  Even with a very mild TBI executive functions involving planning, multitasking, and sequencing are usually compromised.  Because the gifted tend to “coast” relying on the enhances abilities, this fall from grace is into an especially deep pit.”

Note the verbal, the grammatical  error in the statement, and how they support the situation she describes.  Her writings are worth the click and the time it takes to read them.