Tire wear emissions emit 1,850 times more pollution into the environment than exhaust pollutants, according to new research. This is particularly concerning for electric vehicles, as tire wear emissions increase for heavier vehicles, and EVs weigh more than their gas counterparts due to their batteries.

Emissions Analytics initially published research in 2020 claiming that tire particulate wear emissions were 1,000 times worse than exhaust emissions. Generating more feedback than any subject ever tackled by the organization, it decided to do a deeper dive. 

Researchers began testing and analyzing tire wear emissions in more detail across a wider range of driving conditions and performed a detailed chemical analysis of hundreds of new tires.

After performing extensive research, Emissions Analytics determined that tire wear emissions are 1,850 times greater than real-world tailpipe particulate mass emissions.

However, tailpipe particulates are lower on new cars, and tire wear emissions increase with vehicle mass and aggressiveness of driving style. Exhaust filters becoming more efficient has led to tailpipe emissions falling over time, while tire wear emissions are rising as vehicles become heavier and added power and torque are available to drivers.

“On current trends, the ratio may well continue to increase,” said Emissions Analytics. 

Emissions Analytics used high-precision scales to measure tire wear mass emissions weighing all four wheels, tires and rims together, without detaching for at least 1,000 miles on real roads. Then, a sampling system was used to collect particles at a fixed point immediately behind each tire, which was drawn into a real-time detector measuring the size of the distribution of particles by mass and number.

To measure the particles coming out of the exhaust in real-world conditions, researchers used special equipment, including a diffusion charger analyzer to check the number of particles by weight and a condensing particle counter to count the number of particles. Both of these tools were used together with a portable system designed to measure the overall flow of exhaust gases from the vehicle.

As a result, distance-specific mass and number emissions were derived and compared to equivalent tire metrics.

The mass wear from new tires is 16 times greater than the maximum permitted for the tailpipe, but 3,650 times greater than actual tailpipe emissions. The difference falls to 1,850 times greater when considering the full-life average tire emissions.

The increased emissions from aggressive driving highlight the potential risks associated with the heavier weight of battery-powered EVs.

“Half a tonne battery weight can result in tire emissions that are almost 400 times greater than real-world tailpipe emissions, everything else being equal,” said the organization. 

Emissions Analytics revealed that cautious driving in battery-powered electric vehicles can mitigate the increased tire wear emissions caused by the vehicle’s additional weight, potentially resulting in lower tire wear than that of poorly driven internal combustion engine vehicles. It further points out the differences in how tire and tailpipe emissions interact with our environment, with tire emissions primarily affecting soil and water and exhaust emissions lingering in the air, thereby underscoring the challenges in evaluating their overall effect on public health and the environment.

The preliminary findings suggest that the ultrafine particles produced by tire wear, which represent a substantial portion of emissions, could have far-reaching effects on human health due to their ability to penetrate deeply into the lungs and, potentially, the bloodstream.

However, the research is far from conclusive. The variability in chemical composition and toxicity of tire emissions points to a significant gap in our understanding of their environmental and health implications. 

With hundreds of different compounds identified in tires, some of which are known carcinogens, the need for further study is evident. 

As this body of research expands, Emissions Analytics is actively looking for contributors and collaborators who can aid in this crucial investigation. 

“We are looking to talk to anyone interested in research in this area,” concluded the research.