Are tire emissions 1,000 times worse than exhaust emissions?
Research has not demonstrated that tire emissions are 1,000 times worse than exhaust emissions. The claim that tire emissions are 1,000 times worse than exhaust emissions is based on the flawed and unscientific suggestion that comparing the weight of different emission types provides a measure of the relative risk that they pose.
The assertion that tire emissions are “1,000 times worse” than exhaust emissions is sensationalist and disingenuous. It is a misrepresentation of an Emissions Analytics claim that the weight of tire-wear emissions are 1,000 times greater than exhaust emissions per kilometer driven.
Emissions Analytics’ comparison of tire wear particle emissions and exhaust emissions are not credible because their comparison did not make consistent use of vehicles or test conditions. To the admission of Emissions Analytics’ chief executive, this figure comes from a test performed on a car driven in such a way as to maximize tire emissions (“driven as crazily as you could, really pushed it”). Driving style is known to be the main factor of tire wear (Le Maitre et al., 1998), but the extreme measures adopted by Emissions Analytics are not representative of normal driving and would result in a tire lifespan of not more than 500km.
Furthermore, the assertion that tire emissions are 1,000 times worse than exhaust emissions does not take into account the different potential risks to health and the environment from particles of different weight and size. Exhausts emissions are extremely tiny airborne particles that pose a greater risk of entering living organisms by inhalation; whereas TRWP are typically bigger in size and weight, and it is estimated that as little as 2% of total TRWP are released to the air (Unice et al., 2019a, b).
Overall, the Emissions Analytics approach did not follow the basic principles of science and has not been validated as an accurate way to evaluate tire and road wear particle (TRWP) emissions. The Emissions Analytics data are not published in any peer-reviewed scientific journals and the only information regarding the tests that they perform comes from their own website, which mentions the use of “a proprietary sampling system”.
There is no detailed description of the methodology. There are no pictures of this sampling system, no identification of the instrument that they describe as a “real-time detector measuring the size distribution of the particles by mass and number,” no description of the air flow rate of the sampling device, and no information about any techniques critical for accurately capturing or detecting particles in a moving air stream.
Emissions Analytics’ claims have been debunked by transport professionals and independent experts.
