Emissions Analytics finds pollution from tire wear can be 1,000x worse than exhaust emissions
08 March 2020
Pollution from tire wear can be 1,000 times worse than a car’s exhaust emissions, Emissions Analytics has found. Emissions Analytics is an independent global testing and data specialist for the scientific measurement of real-world emissions and fuel efficiency for passenger and commercial vehicles and non-road mobile machinery.
Harmful particulate matter from tires—and also brakes—is a growing environmental problem, and is being exacerbated by the increasing popularity of large, heavy vehicles such as SUVs, and growing demand for electric vehicles, which are heavier than standard cars because of their batteries.
Source: California Air Resources Board (ARB)
Vehicle tire wear pollution is completely unregulated, unlike exhaust emissions which have been rapidly reduced by car makers due to the pressure placed on them by European emissions standards. New cars now emit very little in the way of particulate matter but there is growing concern around non-exhaust emissions (NEEs).
Non-exhaust emissions are particles released into the air from brake wear, tire wear, road surface wear and resuspension of road dust during on-road vehicle usage. No legislation is in place to limit or reduce NEE, but they cause a great deal of concern for air quality.
NEEs are currently believed to constitute the majority of primary particulate matter from road transport, 60% of PM2.5 and 73% of PM10. In the 2019 report ‘Non-Exhaust Emissions from Road Traffic’, the UK Government’s Air Quality Expert Group (AQEG), recommended that NEE are immediately recognized as a source of ambient concentrations of airborne particulate matter, even for vehicles with zero exhaust emissions of particles—such as EVs. (Earlier post.)
To understand the scale of the problem, Emissions Analytics performed some initial tire wear testing. Using a popular family hatchback running on brand new, correctly inflated tires, it found that the car emitted 5.8 grams per kilometer of particles.
Compared with regulated exhaust emission limits of 4.5 milligrams per kilometer, the completely unregulated tire wear emission is higher by a factor of more than 1,000. Emissions Analytics notes that this could be even higher if the vehicle had tires which were underinflated, or the road surfaces used for the test were rougher, or the tires used were from a budget range—all very recognizable scenarios in real-world driving.
The challenge to the industry and regulators is an almost complete black hole of consumer information, undone by frankly out of date regulations still preoccupied with exhaust emissions. In the short term, fitting higher quality tires is one way to reduce these NEEs and to always have tires inflated to the correct level.
Ultimately, though, the car industry may have to find ways to reduce vehicle weight too. What is without doubt on the horizon is much-needed regulation to combat this problem. Whether that leads to specific types of low emission, harder wearing tires is not for us to say—but change has to come.—Nick Molden, CEO of Emissions Analytics
Lets assume a set of tires lasts 50,000 km and loses 10% of it's mass.
5.8 g x 50,000 km / 4 tires / 1000 g to kg = 72.5 kg
Each tire is losing 72.5 kg which means each tire would weigh about 725 kg to start with. My car weighs 740 kg, that's a huge tire for a "popular family hatchback ".
I think the people at Emissions Analytics have been inhaling too much exhaust fumes.
Posted by: Keith Ruddell | 08 March 2020 at 07:36 AM
Brake dust would be bad, use HEV/EV with regen, less dust.
Posted by: SJC_1 | 08 March 2020 at 08:04 AM
5.8g/km is per car, not per tire
Average tire life is around 40,000 km
So 232kg loss over the life, or 58kg per tire
Clearly impossible, but the wear may be differentially loaded as the experiment was specified as being on brand new tires.
But it would appear that tire wear is likely still way more than particulates from exhaust emissions.
Posted by: Davemart | 08 March 2020 at 08:21 AM
I would guess the problem with the figures is due to differential wear for brand new tires.
They were sloppy in not identifying this.
Just the same, if you knock off an order of magnitude you end up with a figure of around 5.8 kg loss over the tire life, per tire, and you are still talking about 100 times the particulates of the exhaust.
Posted by: Davemart | 08 March 2020 at 10:23 AM
The tyre and brakes emission needs to be studied analyzed and not be understimated BUT this is sensationalistic and attention grabbing.
Firstly the method of testing as you can read from Emission Analytics "we stacked the decks by choosing the cheapest tyres, ballasted the car heavily, chose a track with average surface quality and designed a test cycle with high speeds andmuch cornering." , so basically they ran an weighted car like they stole it on a track with the cheapest tyre they could find and then compared the weight loss of rubber with the supposed weight limit of the gaseous tailpipe emission that should be emitted in a vicar driven omologation cycle , personally i don't think it's very fair.
Also they admit that the tyre emission are mainly large chunks of material that is mostly made of particles that are 1000x times bigger than the micro and nanoparticulate ,the latter also tend to linger in the air that we breathe.
Posted by: Vittorio Piccotti | 08 March 2020 at 06:53 PM
What an, pardon my French, idiotic way to assess tyre wear. Here's a simpler, more reliable one:
Find out how many mm of tire is worn off on average (worst case: down to the legal limit) and multiply that by Pi and the diameter of the tyre. Then divide by the number of km/miles driven for a tyre, and viola, you have the per-km tyre wear. You could get that number by dividing the publically available number for miles driven annually for passenger vehicles by the number of tyres sold. It's really a quite simple half-hour desk top study to get right to within 10-20%.
It sounds like someone needed an excuse for renting a race track.
Posted by: Thomas Pedersen | 09 March 2020 at 02:14 AM
I think there are two main take-home messages from this study: 1) There are many other sources of particle emissions than the tailpipes and 2) This field should be studied in much more detail before conclusions are made. For sure, we already knew about that there were such gaps in the knowledge.
Posted by: Peter_XX | 09 March 2020 at 12:07 PM
If you weigh the tire you might lose 1 kg per 30,000 miles.
This would be a lot with 1 million cars in the city, but not much elsewhere.
Posted by: SJC_1 | 09 March 2020 at 08:24 PM
According to a companion study (https://www.emissionsanalytics.com/news/2020/1/8/burning-issue-tyres-and-air-quality), most of the tire PM mass is >PM2.5, and even >PM10.
However, there are still relatively high PN emissions in the nano-particle size range.
Posted by: Carl | 10 March 2020 at 10:01 AM
How on earth did we cope back in the days when brake pads were made with asbestos?
Posted by: Scott | 12 March 2020 at 02:03 PM