Wildfire smoke: How it affects air quality

Wildfire smoke: How it affects air quality




People who have lived most of their lives in the West often talk about the glory days — back when mountain towns still felt like hidden gems (and when home prices reflected that). Recently, nostalgic images of the mountain towns of yesteryear have added another idyllic quality — summer skies not filled with smoke.

Over the past few years, summer has become synonymous with wildfire season. And where there’s fire, there’s even more smoke.

For generations, vehicle and industrial emissions have been responsible for the majority of air pollution across the West. But the quantity of “smoke days” has increased by nearly two full days every year since 2005, rising above 40 days per year. Now, wildfire smoke is responsible for up to half of the particulate matter pollution in the West, and up to 25% nationwide, according to a 2021 study from Stanford University.

“I remember up until about 2000, we rarely had bad smoke in Missoula,” Bob Yokelson, an atmospheric chemist at the University of Montana, says. “And now, pretty much the second half of August and the first part of September, you can almost count on it being crappy air quality. Last summer we even had smoke in July.”

In August 2021, Salt Lake City – which is already incredibly vulnerable to air pollution – experienced the worst air quality in the world.

Yokelson is a wildfire smoke expert — studying its composition and chemical properties — and can reel off complex smoke data and research casually. But beyond his extensive background studying wildfire smoke, Yokelson also lives in an area with a millennium of wildfire history — and as those wildfires grow in size and severity, has had to adapt to the subject of his research just like everyone else.

“I can look out the window and if I can’t see the mountain (I don’t go outside),” he says, referring to the Rattlesnake Mountains that cradle the valley Missoula lies in. “Like, OK, it’s smoky so maybe I shouldn’t do my big 20 mile run today. Or maybe I should work on cabinets instead of the roof. Or maybe we should, you know, do soccer practice on Wednesday instead of Thursday.”


How did the West get here — a time that some have dubbed the “Pyrocene,” a fire age, cloaked in toxic air? Smoky summers are only a symptdn-om of a much larger issue in this case. While there are myriad overlapping problems that have contributed to more intense and destructive wildfires, the most fundamental are management practices and changing climate conditions.

The most widespread and impactful forest management policy throughout the 20th century in the United States was full-suppression firefighting, which very effectively removed fire from landscapes. We’re now witnessing the consequences of those policies that kept all wildfires from burning. Namely, forests that haven’t been allowed to burn in a century have become overrun with vegetation and are thus more prone to disease, drought sensitivity and the inevitability of wildfires doing what they’ve always done — but with hotter temperatures, higher consequences and more smoke.

We’ve also added the effects of climate change to the mix; these effects are varied but can look like more extreme weather patterns, diminished snowpack or increased drought, and other climatic variations that exacerbate wildfire potential for longer periods through the year.

As wildfires driven by climate change and mismanagement continue to increase by almost every conceivable measure, it’s clear that communities across the United States will suffer from poor air quality for longer stretches every summer and fall. These impacts will not only affect the communities hardest hit by wildfires, or even just those living in the West. Recent fire seasons have shown that smoke from California, Oregon, Washington and even British Columbia can affect air quality as far away as the East Coast and Europe.

“The reality is that we’re just going to see more and more fire,” says Natasha Stavros, the director of the Earth Lab Analytics Hub at the University of Colorado Boulder. “This means smoke is going to be more real, and it’s going to be something we have to think about more.”


Have you ever checked the air quality report on a summer day? These reports‚ which you can access online at AirNow.gov, are one of the most helpful tools we have as individuals to check whether the air outside is safe on a day-to-day basis. It shows the concentrations of gasses and particulates in the atmosphere at any given time. A daily air quality index (AQI) report can range from zero to higher than 500 — numbers that are increasingly common in areas vulnerable to wildfire smoke.

Yokelson explains that particulate matter is the primary driver of unhealthy air quality following wildfires. Fine particles are especially harmful, as they can be inhaled deep into the lungs and even into the bloodstream. They are largely responsible for the long-term health impacts of smoke exposure, like chronic obstructive pulmonary disease and certain cancers.

When wildfire smoke begins to block out the sun, air quality has likely breached the 150- 200 range of the AQI system, which is considered “unhealthy.” Above the unhealthy tier is “very unhealthy,” ranging from 201 to 300. Anything above 301 is considered “Hazardous.”All three of these tiers may have notable impacts on those with existing medical conditions — considered “sensitive” groups by the Environmental Protection Agency — and on the entire population in affected areas.

Smoke from recent wildfires has regularly exceeded AQI values in recent years, with AQIs well over 500 being measured in some communities over the last few summers — summers marked with air so hazy with pollution that it crowds out light completely, reducing the sun to a dimmed orange bulb in the sky and making headlights necessary in the middle of the day.

These extreme smoke impacts are often limited to areas with certain topographic characteristics that keep smoke in valleys and drainages, “socking in” communities for weeks or months at a time in some cases. But extremely high AQIs are now occasionally seen in major metropolitan areas far beyond the actual burn areas — Portland, Salt Lake City, Los Angeles and other major cities have all experienced severe smoke impacts over the last two years alone.

The Portland area had never experienced “unhealthy” on the AQI scale before 2020; however, following the Labor Day fires across Oregon and Washington in September of that year, the city ended up logging three “Very Unhealthy” and five “Hazardous” days that month alone. In 2021, Salt Lake City — which is already incredibly vulnerable to air pollution — experienced some of the worst air quality in the world for multiple days in August.

This takes a toll on folks’ health. Older adults and children are especially susceptible — as elders tend to have a higher likelihood of preexisting conditions that can be exacerbated by smoke exposure, while children inhale more air per pound of body weight compared to adults, leading to more smoke inhalation on days with poor air quality.

According to a recent study from the University of Georgia, “fresh” smoke — or that which hasn’t aged in the atmosphere — can cause damage to the mitochondria, which are responsible for processing food and energy production at the cellular level. On the other hand, smoke that has traveled beyond the immediate fire area can grow more toxic over time, leading to excess free radical production in the body, which can ultimately lead to cell death, according to the European Research Council.

Experts say these health impacts can be lessened with a few key actions: The first and most obvious is to limit time outside on particularly smoky days. Others include installing HEPA filters or an air purifier for your home, wearing an N95 mask if you need to be outside in the smoke and increasing access to “clean air shelters” for residents who cannot ensure clean air at home.

And while the recommendations for in-home filters and choosing to stay indoors during the worst days of wildfire smoke pollution during the summer will continue to flood the media, not everyone has an equitable opportunity to reduce the risks of the persistent exposure to poor air quality.

For that reason, Oregon has recently developed protections for agricultural workers, with new Occupational Safety and Health Administration rules related to smoke and heat exposure that were to be implemented starting in June and July. These rules require paid breaks to take refuge from excessive heat or smoke exposure and require that employers provide N95 masks for their employees during the fire season. California has implemented similar measures, though genuine enforcement of these measures has been brought into question. And while not enough research has been done to identify exactly what types of health disparities exist in vulnerable communities, it’s still widely understood that these communities will continue to be inordinately impacted by increasingly bad fire seasons and air quality.


How wildfire smoke is affecting people right now is a massive concern — but not our only one. Standards from the EPA have lessened the impacts of fossil fuel pollution across the United States over the last 60 years, but wildfire smoke is now rapidly countering those gains. It’s long been assumed that wildfire smoke isn’t as harmful as fossil fuel pollution; however, it’s now clear that wildfire smoke has similar levels of toxicity, especially as fires affect more homes, vehicles and infrastructure — all of which create more toxic smoke when they burn.

Yokelson recalls how poor air quality in Los Angeles in the ’50s spurred the realization that air pollution was a nationwide problem that needed to be addressed. “We began cracking down on things like cars and factories, and all kinds of dangerous emissions of pollutants,” he says. “We were making tremendous progress. But now in the last 10 years or so … we’re starting to reverse the progress we made by cleaning up our industries and our cars, because of the increased wildfires.”

So how do we have any hope for a future where the air is clear and the outdoors is safe?

One seemingly paradoxical solution to worsening air quality due to wildfires is – get this – more fire.

Experts like Yokelson agree that one seemingly paradoxical solution to worsening air quality due to wildfires is — get this — more fire.

More fire can come in the form of prescribed fires or “controlled burns,” in addition to indigenous burning practices. These types of fires are set by practitioners and tribes in the “offseason,” when conditions are not as volatile as they are in the summer. This type of burning allows for some level of control over how the fire burns, as well as how much land is treated.

At their best, these burns clear excess vegetation and — if done consistently in the right places — can lessen fire intensity should a wildfire burn into the area, giving firefighters a better chance of suppressing the fire in these “treated” areas. However, windows for getting this type of ecologically beneficial fire on the ground are shrinking by the year. It’s also important to note that prescribed fire is no knight in shining armor for our fire problem — there will still be smoke and its negative side effects. But it is an important step in building forest resilience and, hopefully, lessening future smoke impacts from megafires.

Prescribed fire smoke is also demonstrably less toxic than wildfire smoke.

If you’ve ever seen a nice, clean-burning campfire, you can imagine what would happen if you threw a green branch on it. Smoke.

Prescribed burns limit what — and how much — is burned. When less fuel is consumed, that fuel produces less smoke, and that can add up to about 18 times less pollution per area, according to Yokelson.

While the reality of the prescribed burning of millions of acres of land that hasn’t been allowed to burn in a century is not necessarily optimistic, it could be one of the most important tools we have to limit both wildfire and smoke impacts in the future, especially if combined with meaningful community adaptation to wildfires and smoke. These adaptation measures could include improving access to air filters and purifiers, educating communities about the benefits of fire and how to improve their resilience to it, and developing community clean air shelters for those who are unable to protect themselves in their own homes. It will also require more research from scientists to develop a stronger understanding of wildfire smoke and its increasing public health impacts.

“I’m very excited about all of this work that’s being done to try and think about ways that we can protect people’s health in the face of this exposure,” says Colleen Reid, assistant professor in the geography department at the University of Colorado Boulder. “We can try really hard to do more prescribed burning, or more forest thinning, or all sorts of things to try and lessen the fires. But that’s going to take a long time. And in the meantime, we need to protect people’s health.”


We’re all likely guilty, to some degree, of taking life in the West for granted. We get mountain views and after-work hikes and meadows of wildflowers and swims in lakes, but we don’t often consider what the wilderness requires back from us. Increasingly volatile wildfire seasons have forced us to grapple with how deeply intertwined our lives and the wild spaces we love are.

The days of begrimed haze are likely not going anywhere. This isn’t good news but perhaps it will spur some critical action on our part. We can no longer escape the reality that living in the West will require significantly more accountability to the places and landscapes where we live — or, at the very least, a capacity to coexist with the smoke that settles.

This story appears in the July/August issue of Deseret MagazineLearn more about how to subscribe.





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