Dear Dot: Are (Winter) Tires Bad for the Environment? 

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Dear Dot,

I recently swapped out my regular tires for winter ones. But what impact do winter tires have on fuel economy? What about pollution? Are certain tires better for the environment than others?

–Bob

The Short Answer: While we wait for regulations to catch up and tackle the ubiquity of toxic materials in tires, and while researchers are at work seeking more sustainable materials from which to make tires, for now, we’re mostly stuck with the toxic ones. 

So let’s control what we can — our driving. When possible, leave the car at home and walk, cycle, e-bike to your destination. Or take public transportation. When you are behind the wheel, don’t drive aggressively. Ease into braking and acceleration. Don’t zip between lane changes. Purchase the right-sized tires for your cars. Larger tires burn more fuel. Smaller tires wear out more quickly. And when your tires have well and truly rolled their last mile, dispose of them responsibly. There is tire recycling available in the U.S. and in Canada

Dear Bob,

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While swapping out all-season tires for a winter version isn’t a universal experience (my daredevil New England colleagues tell me they don’t do it!), it’s a ritual that has forever been a part of my Canadian driving experience. 

Each November, Mr. Dot hauls out his car jack, rolls the winter tires out of our shed, and proceeds to undertake the loathed task. And then, for at least a week after, he moans about his sore back and vows to pay someone else to do this job next year. It’s a ritual as Canadian as vinegar on fries and maple syrup (the real stuff!) on pancakes.

While it’s true that my fuel economy goes down in the winter, it’s not entirely due to winter tires. Winter tires do increase what those in the biz call “rolling resistance” — deeper treads create more friction between road and tire, thereby requiring more fuel to move the vehicle — but other culprits have a more significant impact on winter fuel economy. 

The U.S. Department of Energy notes that cold-weather driving decreases fuel efficiency by roughly 15–20 percent in cars with internal combustion engines, 30–34 percent in hybrids, and about 40 percent in EVs due to a number of factors, including heated seats and steering wheels, idling to warm up the vehicle, and defrosters. Most of the reduced efficiency (two-thirds!) can be blamed on heating the car’s cabin. 

And considering that winter tires contribute to safer driving on icy and snowy roads, we Canadians put fuel economy concerns aside in favor of getting where we’re headed without incident. 

But tires — winter and otherwise — do have an altogether different environmental impact, and it’s something that two researchers, both of whom know winter in their bones, are keen to tell us about.

Marcus Brinkman is an Associate Professor in the School of Environment and Sustainability at the University of Saskatchewan (have you experienced winter in Saskatchewan, Bob? Brrrr); and Elisabeth S. Rødland has a PhD in environmental chemistry and works at the Norwegian Institute for Water Research. (Do you know how cold it gets in Norway, Bob?)

While both Elisabeth and Marcus are winter-tire adherents, their work has focused on the environmental impact of microplastic particles released by tires generally. 

“One of the issues with tires,” Marcus says, “is all that material that you’re losing over the years and which prompts you to replace the tires when the tread is worn down … all that material lands on the road.” He doesn’t want to bog us down with what he admits is “a lot of math,” but, essentially, “it’s tons and tons — hundreds of thousands of tons of material that we distribute on our road surfaces.” That material, he says, either becomes airborne or gets washed off road surfaces into waterways. 

Both he and Elisabeth point to fascinating research out of Washington State. Community organizations, scientists, and various levels of government were trying to solve a mystery regarding Pacific Salmon, a crucial species economically, culturally, and environmentally, that were experiencing what is referred to as “mortality events,” (what you and I, Bob, might simply understand as a whole lot of dead fish). It was clear that these “events” followed big rainstorms after long dry periods. “The fish started dying within less than an hour,” Marcus says. “Within minutes.” Thanks to advances in analytical chemistry, the mystery-solvers’ tool box gained something called non-target chemical analysis, which, after close to two decades of trying to figure out the culprit for these spontaneous fish deaths, enabled researchers to discover that there was a strong signature of tire compounds in the bodies of the dead fish. And from that, they identified one chemical in particular that seemed to be entirely responsible — an antioxidant added to tires so they don’t get too brittle. It’s called 6PPD-Quinone, and it’s toxic enough that, as Marcus puts it, as little as a particle the size of a single grain of salt in an Olympic swimming pool can be enough to kill fish. Indeed, researchers have created a test to detect 6PPD-Quinone at one part per trillion. 

Tires that shed microplastics are shedding more than one specific chemical. What else is coming off remains a bit of mystery, largely because the tire industry doesn’t want to tell us what other materials they’re using in their tires.

Yale Environment 360 reported that “the chemical continues to be used by all major tire manufacturers and is found on roads and in waterways around the world. Though no one has studied the impact of 6PPD-q on human health, it’s also been detected in the urine of children, adults, and pregnant women in South China. The pathways and significance of that contamination are, so far, unknown.”

But, of course, tires that shed these microplastics are shedding more than that chemical. What else is coming off remains a bit of mystery, largely, Elisabeth says, because the tire industry doesn’t want to tell us what other materials they’re using in their tires. “They tell us it’s impossible because it’s trade secrets,” she says, “which makes the science behind it very difficult.” Scientists have to try and figure it out by analyzing samples. 

And though tires are typically blended with natural rubber, she says, and would have a lower concentration of synthetic polymers than, say, our polyester clothes, “tires are defined as one of the largest sources of microplastics in the world.”

Researchers came to this conclusion by examining how much wear tires undergo, recognizing that all the stuff that started on a tire but was no longer there when tires were tested after use had to go somewhere. And that somewhere is into soil, into water, into all our environments. 

Tracking it down was no easy feat, Elisabeth says. The shedded particles are microscopic, for one thing. And they’re black — just like asphalt and bitumen particles. But organic material breaks down when heated to super-high temperatures — about 700 degrees Celsius — making molecule samples smaller and easier to differentiate. “By looking at all of these molecules,” she says, “and finding what type of molecules are in the sample, we can determine what type of plastics were in there.” In the winter, they take snow samples and assume that any plastics they find in them are from winter tires. They’ve also compared the amounts of plastics found in samples taken close to roads and from farther away. “We’re slowly trying to build up this knowledge to understand where [these plastics] end up, what happens to them when they end up in nature.” She’s confident that, although there are wide ranges of amounts of particle dispersal depending on size and type of car, the average vehicle’s tires are responsible for the release of two kilos (slightly less than four-and-a-half pounds) of microplastics per year. 

All of which leaves researchers and scientists with more questions. “It’s figuring out the hotspots where our [microplastics from our] tires are ending up,” Elisabeth says, and it’s sorting out which species are sensitive to which additives. “The Atlantic salmon that we have in Norway, for example, hasn’t been found to be very sensitive, which is a big relief for us,” she says. “But that doesn’t mean that there are no effects found for other species or other fish or other aquatic organisms.” 

So are winter tires a bigger problem because of their deeper treads? Not necessarily, Elisabeth says. “Tires, in general, are a problem.” 

Which leaves us … where exactly? 

Elisabeth has some ideas for what we can do. “There are simple things,” she says, “like drive less. Take public transport.” But, even die-hard drivers can take steps. “We found significant correlation between the amount of tire particles and traffic speed,” she says. Higher speed causes more friction with the road surface, ergo more microplastics. Braking harder (also often due to higher speeds), puts more wear on your tires. And more lane changes also put more wear on tires. 

If you’re an EV driver, stifle your smugness. Turns out that electric vehicle drivers, because their EVs have greater torque, accelerate and brake faster, which — you guessed it, Bob! — causes tires to shed more microplastics. Consequently, tires on EVs require replacing more often, which is … not great environmentally. 

I grow tired, Bob. So let’s wrap this up: While we wait for regulations to catch up and tackle the ubiquity of toxic materials in tires, and while researchers are at work seeking more sustainable materials from which to make tires (you can look for those, such as Pirelli, that use 50 percent bio-based materials), for now, we’re mostly stuck with the toxic ones. 

So let’s control what we can — our driving. When possible, leave the car at home and walk, cycle, or e-bike to your destination. Or take public transportation. When you are behind the wheel, don’t drive aggressively. Ease into braking and acceleration. Don’t zip back and forth between lanes. 

Purchase the right-sized tires for your cars — larger tires burn more fuel; smaller tires wear out more quickly. 

And when your tires have well and truly rolled their last mile, dispose of them responsibly. There is tire recycling available in the U.S. and in Canada

Thanks for your question, Bob. Now, if you’ll excuse me, Dot is going to take a nap.

Non-toxically,

Dot

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