Open letter: Regulating pollutants from tyre emissions

From Nick Molden, Co-Founder of the AIR Alliance and Dr Andreas Mayer, Chairman of the Scientific Committee of the VERT Foundation

27 June 2023: To whom it may concern

An important and groundbreaking part of the proposed Euro 7 regulation involves setting a limit value for tyre wear emissions. This is particularly important as vehicles continue to become heavier, not least with the growing sales of battery electric vehicles. However, the current proposal covers only the total mass of emissions and, therefore, ignores both ultrafine nanoparticles and chemicals released from the tyres. Without changes, it is likely that tyres will be re-engineered to deliver lower emissions of larger particles but potentially at the cost of the release of more invisible nanoparticles and potentially toxic chemicals.

Therefore, we would call on the European regulators to initiate work as soon as possible on a second phase to Euro 7 tyre emissions that would expand the coverage to both nanoparticles and chemical release in real-world conditions.

Regulating mass, and thereby larger particles, is important particularly for marine pollution, as the over 50% reduction in the population of coho salmon on the west coast of North America shows. This die-off has been conclusively linked by academics to a preservative compound found primarily in tyres. By this very fact, it can be seen that it is not only the particles themselves that is causing the issue, but the chemicals leaching out as those particles settle in the environment. Furthermore, these same tyre chemicals are being seen on a widespread basis in human foodstuffs and excreta.

These chemicals are typically volatile organic compounds. Within this broad collection there is group of aromatic compounds, many of which are carcinogenic, such as polycyclic aromatic hydrocarbons (PAHs). To some extent these are regulated at the tailpipe currently through the total hydrocarbons limit value, although this could also be made more stringent and targeted to the most potentially toxic individual compounds. Eight compounds are also restricted under the REACH chemical regulation, but the coverage is too narrow and the limits too accommodating. Emissions Analytics presented on this topic at the fifth session of the UNECE Task Force on Tyre Abrasion on 30 September 20221. There is regulatory precedent from Switzerland, where the 2014 particle number standard (SN 277206:2014) included a secondary emissions test for certain target chemicals—including PAHs and nitro-aromatics—based on the US Clean Air Act section 2022.

Nanoparticles are already regulated at the tailpipe since Euro 5. This intervention has been highly successful in reducing in-use emissions by particle filters in most vehicles, and measurement of these ultrafine particles is being expanded into the periodic technical inspection regimes in a number of European countries, which in all likely will deliver further significant reductions in real-world particle emissions. As the evidence for the negative health outcomes from chronic and acute exposure to nanoparticles becomes ever clearer, the value of this regulation grows. Yet, there are no current plans to regulate the same particles from tyres, despite tyres being made of the same underlying fossil materials as liquid fuels. Multiple academic studies have shown that tyres release large numbers of these particles in real-world use. Particle number measurement from tyres has been included for many years in the investigations of the Joint Research Centre of the European Community and the Particle Measurement Programme3, and such efforts should be accelerated to address this growing environmental issue.

In summary, we call on European regulators to apply the same approach they have applied to the tailpipe to the growing issue of tyre emissions. Particle mass, particle number and volatile organic compounds released from tyres must all come within a successful Euro 7 regulation at the earliest opportunity.


Nick Molden, Co-Founder The AIR Alliance, Chief Executive Emissions Analytics
Dr Andreas Mayer, Chairman of the Scientific Committee, VERT Association



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