Do car tires create more pollution than exhaust fumes?

Question

The article Exhaust fumes don't pollute nearly as much as this part of a car claims that tires cause more pollution than exhaust fumes.

Car tires are worse for the environment than exhaust fumes

In an article for the Chartered Institute of Environmental Health, Kerry Taylor-Smith wrote, "Car tires may represent a greater threat to the environment than exhaust fumes, with a new study suggesting tire wear produced almost 2,000 times more particle pollution."

Is this correct?

Answer 1

tl;dr

• The study only focuses on particulate emissions.
• It does not take into account other forms of pollution.
• It does not claim all tire emissions are worse for the environment than all exhaust fumes.
• The ratio is so high, in part, because tailpipe emissions have gotten so low.
• The study concludes more research and regulation is needed for tire emissions.

The source does not support the claim.

The article makes claims such as

Exhaust fumes don't pollute nearly as much as this part of a car

and

Exhaust fumes are the least of our problems

and

Tires pollute more than exhaust

and

Car tires are worse for the environment than exhaust fumes

These are all misleading, overly general statements which are not supported by the study.

The study is about particulate emissions only.

Their claims appear to be based on studies and presentations by Emissions Analytics. In their article Gaining traction, losing tread Pollution from tire wear now 1,850 times worse than exhaust emissions adds some nuance. As they note...

Quoting such ratios, however, needs careful interpretation.

The study only focuses on particulate emissions. It does not take into account other forms of pollution from your car's tailpipe nor tires. It does not claim all tire emissions are worse for the environment than all exhaust fumes.

The ratio is high, in part, because tailpipe emissions are so low.

The fundamental trends that drive this ratio are: tailpipe particulate emissions are much lower on new cars, and tire wear emissions increase with vehicle mass and aggressiveness of driving style. Tailpipe emissions are falling over time, as exhaust filters become more efficient and with the prospect of extending the measurement of particulates under the potential future Euro 7 regulation, while tire wear emissions are rising as vehicles become heavier and added power and torque is placed at the driver’s disposal. On current trends, the ratio may well continue to increase.

Which is to say...

1. Tailpipe emissions have fallen to almost nothing.
2. Heavier cars cause more wear on tires.
3. Aggressive driving of more powerful cars causes more wear on tires.

Claims 2 and 3 have been used as way to claim EVs pollute worse than Internal Combustion Engine (ICE) vehicles, because they tend to be heavy and have more torque. However, they note that tire wear is largely a function of driver behavior and regenerative braking.

The excess emissions under aggressive driving should alert us to a risk with BEVs: greater vehicle mass and torque delivered can lead to rapidly increasing tire particulate emissions. Half a tonne of battery weight can result in tire emissions that are almost 400 more times greater than real-world tailpipe emissions, everything else being equal. Nevertheless, it is important to say that a gentle BEV driver, with the benefit of regenerative braking, can more than cancel out the tire wear emissions from the additional weight of their vehicle, to achieve lower tire wear than an internal combustion engine vehicle driven badly.

They conclude now that tailpipe emissions are so low, its time to study and regulate other forms of polluting emissions from cars.

The aim is to bring transparency and insight to an area that has historically been under-researched, but which has now been thrown into the spotlight with ever-heavier vehicles and rapidly cleaning tailpipes.