Intuition might suggest that exhaust gases are the number one source of automotive pollution, but tires are also very problematic.
This is a fact long established; the traditional automobile, with its fossil fuel engine, is a first class ecological disaster. But the source of this pollution within the car, on the other hand, is much less intuitive than one might think.
In any case, this is the conclusion of a series of studies carried out by Emissions Analytics, a company specializing in the measurement of atmospheric pollutants. They were interested in the smallest caliber of fine particles – those no larger than 23 nanometers in diameter.
Their size makes them difficult to quantify and study. For this reason, according to the Guardian, they are not regulated by either the European Union or the United States. A real nonsense in terms of public health. Because of their size, these particles can lodge in the organs via the bloodstream, and thus considerably increase the risk of cancer.
Tire wear more polluting than the exhaust?
When looking at a car, the origin of these particles seems quite obvious. The combustion of fuel takes place in the engine; the majority of fine particles must therefore come directly from the exhaust, right? Missed; according to this study, the main culprits would be above all the four crowns of rubber that come to garnish your axles.
During testing, the researchers determined that the exhaust produced on average 0.02 milligram of fine particles per kilometre. Tires, on the other hand, produced on average 36 mg/kg – almost 2000 times more fine particles than the exhaust.
And that was normal driving. Also according to the Guardian, when researchers pushed their Mercedes C-Class to its limits with what they describe as a “very aggressive driving”, emissions have reached an implausible 5760mg/km… that is nearly 300,000 times the figure measured at the level of the exhaust of very recent cars.
Obviously, the exact figures must be taken with a grain of salt. The measurements at the level of the exhaust were for example carried out only on vehicles aged 2 to 3 years maximum. They are therefore not representative of the entire vehicle fleet. But overall, the conclusion remains the same. And it will continue to impose itself over the replacement of older vehicles that are more up to standard.
An underestimated aspect of automobile pollution
“Tires are rapidly eclipsing exhaust pipes as a major source of vehicle emissions” explains Nick Molden, one of the researchers behind the study. After years of tougher green standards, he says “the exhausts are now so clean that if we started from scratch today, we wouldn’t even bother to regulate them”.
We obviously have to be satisfied with the relative progress made by the industry on the issue of exhaust gases. However, the same cannot be said for the tires. These elements are highly regulated for all aspects of handling and reliability; on the other hand, it is another story for their composition.
According to the Guardian, it is virtually unregulated. However, Emissions Analytics researchers have identified a large number of highly toxic or carcinogenic compounds. However, each year, the equivalent of 300,000 tonnes of tires is shredded by the asphalt and released into the environment in the form of fine particles, in the United States and Great Britain alone…
An urgent need for regulation
A problematic situation that researchers would like to see changed. They explain that there is an urgent need to regulate tire composition. This would get rid of at least the most problematic compounds. “If we could eliminate the worst half, and bring them up to the level of the best, we could make a massive difference.”, explains Molden. “But at present, there is no regulatory tool or monitoring”, he laments.
The other problem is that unlike exhaust gases, where the situation is improving with the evolution of standards, the problem with tires could be accentuated by industry trends. Indeed, more and more consumers tend to opt for SUV, particularly heavy. This imposes an even greater constraint on the tyres, which therefore tend to wear out more quickly, with all that this implies for fine particle emissions.
To a lesser extent, the problem could also concern electric vehicles. They tend to be heavier than traditional equivalents for equal size, due to the presence of the batteries. But as it stands, the industry still lacks a bit of perspective on this issue. If we refer to current studies, the average tire wear does not really seem to be greater on electric vehicles.
But anyway, after several decades of struggle to clean up vehicle engines and countless controversies over consumption and emissions, it will therefore be very interesting to see how the automotive industry will negotiate this new sharp turn in this context where microplastics are becoming a problem on a global scale.