## ICL briefing paper estimates that 52% of all small particle pollution from road transport comes from tires and brakes

##### 27 February 2023

A new briefing paper from Imperial College London estimates that in 2021, 52% of all small particle pollution from road transport came from tires and brakes. The researchers, from Imperial College London’s Transition to Zero Pollution (TZP) initiative, warn that even though electric vehicles remove the problem of fuel emissions, we will continue to have a problem with particulate matter because of tire wear.

Six million tonnes of tire wear particles (TWP) are released globally each year, and in London alone, 2.6 million vehicles emit around nine thousand tonnes of tire wear particles annually. Despite this, research on the environmental and health impacts of tire wear has been neglected in comparison to the research and innovations dedicated to tackling fuel emissions.

Different shapes and sizes of tire wear particles imaged using scanning electron microscopy showing, relative to each other: (A) a PM10 spherical tire wear particle; (B) a smooth, long and large tire wear particle; (C) a large uneven tire wear particle mass; and (D) a PM10 tire wear sharp fragment resembling a crystal structure similar to silica. Scale bar of 10 μm = 0.01 mm (Mao, 2021) Tan et al.

The Imperial researchers say that the effect of new technologies on the generation and impact of tire wear should be a priority.

In the new briefing paper, a multidisciplinary group of Imperial experts including engineers, ecologists, medics, and air quality analysts have called for as much investment into tire wear research as there is for reducing fuel emissions—and for understanding their interactions.

Tire wear particles pollute the environment, the air we breathe, the water run-off from roads and has compounding effects on waterways and agriculture. Even if all our vehicles eventually become powered by electricity instead of fossil fuels, we will still have harmful pollution from vehicles because of tire wear.

We urge policymakers and scientists to embark on ambitious research into tire wear pollution to fully understand and reduce their impacts on biodiversity and health, as well as research to reduce the generation of these particles.

Where tire wear particles end up, illustrated with model values from Wagner et al., 2018.

As tires break down they release a range of particles, from visible pieces of tire rubber to nanoparticles. Large particles are carried from the road by rain into rivers, where they may leach toxic chemicals into the environment, whilst smaller particles become airborne and breathed in. They are small enough to reach into the deep lung.

These particles may contain a range of toxic chemicals including polyaromatic hydrocarbons, benzothiazoles, isoprene, and heavy metals such as zinc and lead.

Particulate matter from tire wear is a significant source of microplastics in rivers and oceans, and tire wear in cities could pose up to a four-fold greater risk to the environment than other microplastics.

While existing technological interventions, such as filters, and environmental policies could help to control our ecological footprint, there are huge gaps in our knowledge, understanding, and ability to forecast the impacts of tire wear pollution.

Our gaps in understanding make further research and development of new solutions vital so we can limit all types of vehicular pollution. Tire waste does not naturally degrade and instead builds up in the environment, and may interact with other pollutants as well as biological organisms.

—Co-author Dr Will Pearse

The impact of tire wear particles on human health is an increasing cause for concern, and the full long-term effects on our health urgently require more research, the ICL team says.

There is emerging evidence that tire wear particles and other particulate matter may contribute to a range of negative health impacts including heart, lung, developmental, reproductive, and cancer outcomes.

We are growing increasingly concerned by the impact of tire wear on human health. As some of these particles are so small they can be carried in the air, it’s possible that simply walking on the pavement could expose us to this type of pollution. It is essential that we better understand the effect of these particles on our health.

—Co-author Professor Terry Tetley

The researchers argue that reducing tire pollution should be seen as a critical part of making transport cleaner and more sustainable, alongside reductions in CO2 and other exhaust emissions.

The report authors call for policymakers and scientists to investigate the complex problems related to tire-wear pollution, from the basics of wear-particle production, to understanding how these particles affect the health of people and the planet. Potential innovation solutions include particle capture technologies, new advanced materials, and disruptive business models that encourage different transport choices. These need to be coupled to clear policy and regulation and to a broader discussion around urban transport systems.

The research efforts, they say, should include the following:

• Establishing standardized ways of measuring environmental tire wear levels and their toxicity.

• Reducing harm to land and water species and in humans by tightening limits on the use of harmful components in tire materials.

• Launching new trials to better understand the short and long-term effects of different sized particles on the environment and human health.

• Efforts to better understand underlying wear mechanisms and to propose wear mitigation strategies such as reducing vehicle weight, using advanced driving techniques, and ensuring tire materials pass wear resistance regulations.

Resources

• Tan Z, Berry A, Charalambides M, Mijic A, Pearse W, Porter A, Ryan MP, Shorten RN, Stettler MEJ, Tetley TD, Wright S, Masen MA (2023) “Tyre wear particles are toxic for us and the environment.” Imperial College London (2023). doi: 10.25561/101707

• Mao, Y. (2021) “Tyre Thread Ageing Behaviour and Lung Toxicity of Tyre Wear Particles.” MSc. Imperial College London.

• Wagner, S., Hüffer, T., Klöckner, P., Wehrhahn, M., Hofmann, T. & Reemtsma, T. (2018) “Tire wear particles in the aquatic environment - A review on generation, analysis, occurrence, fate and effects.” Water Research 139, 83-100. doi: 10.1016/j.watres.2018.03.051

That is without taking into account road abrasion, which is another major non-exhaust contributor:

https://www.greencarcongress.com/2019/07/20190714-nee.html

So you come out to something of the order of 2/3rds of the emissions are non exhaust, and of course the heavier and faster accelerating the vehicle, the bigger the problem.

I drive the least polluting car there is, it is a manual hyundai accent and also i don't do speeding and i put regular gasoline.

@Gorr,
provided you are using your brakes, you don't drive the least polluting car.

Electric cars and hybrids use regenerative braking; they barely emit brake dust.

Another strong argument for EVs, which can get 250,000 miles on a set of brake pads, about 5x more than an ICE.

With better one pedal driving technology (like regenerative braking to a full stop) even that remarkable feat can be improved. That is happening now.

@electric car insider.com - Only for the early adopters that drive one pedal most often. We have seen the general public just wants to put it in D and drive. Which results in a lot of late braking and brake wear. Less than ICE vehicles, but still not same as you are implying.

@peskanov - If @gorr can slow the car be coasting and using smart engine braking then brake use ends up being about what a BEV is. I drove a 2015 Golf 163K miles and never replaced the brakes (was totaled when another driving turned left in front of me).

Also the extra weight of BEVs has proven out in previous studies to increase the tire wear substantially. ID 4 on average have been wearing thru tires in 10-20K miles. (here in Florida). Also similar road wear from BEV as seen from heavier commercial vehicles.

I don't know the overall emissions total. I would hazard a guess it works in BEV favor. But we need to be realist and not over sell it.

On another thread I posted this exact issue. BEV have 4 to 10 times the tire wear rates of a similar capacity ICE vehicle. 10 to 20K miles is right for a heavy sedan sized BEV at 5000+ lbs on sedan sized tires. I leased a model S because I have solar panels on my roof and wanted free miles of charging. That Tesla absolutely ate expensive tires at 20,000 intervals if you are lucky and do mostly highway. I had taken it from DFW to Houston,Midland,New Orleans and Mobile every three weeks I'm a geologist and those are my work locations. Stopping to super charge was a major inconvenience especially when time pressed it took two stops to New Orleans , three to mobile only one to Houston though. I got tired of having to stop every 250 miles or so. I can handle 600+ in the seat at a time.

Ended up just taking my F250 diesel most of the times and billing the clients for miles but it was using up the life of the asset too fast with no gain in equity in fact it was a loss. the tesla while fun to drive in the city so it got replaced with a GDI KIA commuter car love it @45mpg I have seen as high as 48 pure hwy and I just had a set of Kumho tires low pros at that in 55r17s go 107,000 miles before not meeting inspection specs they still had grooves just not the minimums needed to pass the state sticker.

This is a full sized 5 pass sedan that gets 38,000 miles per year with 1800 mile round trips every three weeks and bumper to bumper city stop/go at each end for weeks at a time. Brakes were done at 85000 and will last till 150/160 for sure. I expect these Kumho's to be the last set it gets it will be traded by 200k so two set of tires and maybe two set of brakes over my useful 200k lifespan thats better than any BEV in cost for sure those telsa tires were also low pros and $200 each every 20k miles vs$130 for Kumho which are OEM for Kia Motors.

I will be getting a new K5 when this one goes to the great car lot in the sky. I.want Kia to make a K5 plug in capable with a 20kwh LiFePO4 bladecell.pack, electric drive units and a small GDI 3cyl that is flexfuel up the compression from 11.3:1 to 16:1 like a diesel with diesel levels of BSFC. E85 can be run at diesel levels of compression. Why because compression ratio is the number one determinate for BSFC. Alternatively going to 14:1 like Mazda skyactive would allow for flexfuel and/or premium 93 to be used but you loss peak BSFC efficiency to allow.for pump gas vs E85 I'm happy with just E85 there are pumps everywhere for it now. For my use the pack would cover all my.needs locally and at my end point destinations with the 3cyl covering the 600+ miles each way at 80-90 mph continuously with no stops for.charging. My current Kia can go 620 miles door to.door at those speeds and still have 2 gallons in the tank left at each end. For my needs I learned I require at least 500 miles real range and 5 min or less refueling times until a BEV can do that with the A.C. Roaring in West Texas at 90mph constantly because of 85 mph speed limits I.won't consider another BEV for me. A plug in K5 with the specs above would be bought tomorrow as a business asset.

@JamesDo:

A fuel cell car could do your runs and still not put crap out of the exhaust.
That is why there is no one answer to decarbonisation.

EPA Tier 3 Bin 0 is classified as a CARB ZEV the air coming out of a T3B0 in cities such as LA or Houston cleaner than the air that went in when measured for NOx,SOx, PM2.5 due to the catalysts and PM filters in the exhaust train. The EPA is now down to individual PPM range of emissions limits at that point trees produce more NOx and PM2.5. The single largest emitter of NOx in nearly every state is coal followed by natural gas turbines guess what makes 60% of the power grids power in the USA yup coal and Ngas.

Fuel cells are an order of magnitude more expensive than a small ICE engine for equal kw of output. The platinum alone in a fuel cell is 10,000 bucks or more. You can go to Harbor freight and get a 30hp engine for less than $500 a 25 kw fuel cell is going to sat you back ten grand or more then you need Gucci expensive carbon fiber tanks to hold H2 and then a whole infrastructure of H2 stations. Or use cheap plastic tanks and liquid fuels use biofuels if you care about CO2 half of Americans don't care about CO2 but they do care about imported oil from countries hostile to the USA. LDV are 60+% of our fuel consumption a good portion of that imported. Going to a affordable small battery pack, electric drive units and a range extender based on cheap motorcycle or industrial engines could eliminate 95% of ALL LDV fuel use that is how you win over the half of Americans who don't give a single care about climate change. Make affordable cars as in$25K or less that can use any fuel and do it at 60+ mpg while allowing the first 45 miles to be from the plug at 8 cents per kwh like we have in Texas that s 2 cents per mile in energy costs.

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