Should Tire and Brake Emissions from Vehicles Be Regulated?

• Upcoming Euro 7 regulations, due to come into force at the end of 2026 in the European Union, will regulate particle emissions from brakes and tires.

• Bosch has built a special testing rig for examining emissions from brake pads and discs in an effort to design components that produce fewer emissions of this type.

• Regulations and studies regarding microplastics and other particulates produced by tire and brake component wear are still in their early stages, as the issue has started to receive regulatory scrutiny just recently.

When it comes to vehicle emissions, most of the focus has been on tailpipe exhaust from passenger cars and light trucks, even if the methods of measuring such emissions have often fallen short of faithfully replicating real-world conditions.

For the most part, automakers have been entrusted by various regulators to police themselves when it comes to emissions given the transparent number of new vehicle models and engines introduced in just a short span of time.

But it's more recently that toxic chemicals generated by tires and brakes have begun to be studied by governments, independent research organizations, and manufacturers alike.

And these chemicals are now understood to be a much larger issue than previously suspected, with the majority of ocean microplastics now believed to be generated by tire rubber.

"Dust shed by tires generates 450,000 metric tonnes of microplastic—particles of plastic that are less than 5 mm in size—per year in the EU, making tire particles the second-largest quantified source of microplastic pollution in the bloc, after paint," the Pew Charitable Trusts noted in March of this year, largely applauding the Euro 7 standard while noting some shortcomings.

These particles, once they are emitted from tires and brakes, can leach dangerous chemicals into the environment that are almost impossible to contain or remove, recent studies have shown.

And the issue itself, from the standpoint of believing that it exists in the first place, may not even require microscopes: As your car's tires age they shrink in size, and all of those fine particles certainly have to go somewhere.

Late last year the European Parliament as well as the Council of the European Union agreed to emission standards for cars and trucks, with a new regulation dubbed Euro 7 set to be enforced by the end of 2026.

The Euro 7 requirements will impact light- and heavy-duty vehicles, regulating tire and brake particle emissions generated by the abrasion of brake pads and discs.

Only tires that will feature an abrasion rate below the Euro 7 standard will obtain type approval in the EU, while different standards will be set for ICE vehicles and EVs for brake particle emissions.

But regenerative braking in EVs perhaps should not be seen as a silver bullet solution to the brake particle issue. EV deceleration, lest we forget, is not done entirely via regenerative systems, as many electric and PHEV models still use brake pads.

"As vehicles get heavier due to electrification, tire-related pollution is set to increase, with estimates that by 2050, 90% of particulate emissions from road transport in Europe will originate from non-exhaust sources—predominantly tires and brakes," noted Natacha Tullis, an officer with Pew's Preventing Ocean Plastics Project.

The Euro 7 tire requirements, meanwhile, are designed to come into force in phases based on tire class, with new tire models being subject to the Euro 7 requirements earlier than all tire models on sale.

While the regulations are an important step in the right direction—even if they feature certain compromises—just how will such particles be tested prior to type approval?

Bosch, a well-known supplier and developer of vehicle components, has recently updated a test rig that has been used to examine brake particle emissions since 2022. Upgrades to this rig have now been revealed after more than a year of work and over €1 million spent on the effort.

"This high-precision system provides Bosch engineers with detailed information on emissions behavior in a multitude of different driving situations," the company notes.

Bosch says the Euro 7 regulations will apply not only to automakers, but also to aftermarket manufacturers of tires and brake pads.

The test rig, which can detect particles as small as PM 1 or less than one micrometer in diameter—exceeding the requirements of the Euro 7 standard—allow engineers to test brake components in different driving scenarios. The rig itself will be used to make improvements to Bosch brake pads and discs.

"As well as helping to meet future emissions limits, the tests are also designed to reduce emissions of ultra-fine particles, which are particularly harmful to health and are not yet included in Euro 7 regulations," Bosch adds.

We are still in the very early years of tire and brake particle awareness and regulations in the EU and elsewhere, with much work to be done on old-fashion internal-combustion emissions. (The clouds of black diesel soot being produced by almost every school bus, for instance, remain an unaddressed daily reality).

The EPA certainly regulates emissions from tire-producing facilities in the US, but not from individual tires in service. However, the EPA is broadly aware of the issue and has discussed it with industry representatives and research organizations.

It is clear that governments, organizations, and suppliers are waking up to the dangers posed by microplastics to ecosystems and to human health, at least in the EU, even if regulations are still seen as lagging behind the actual emissions.

Should particle emissions from tires and brakes be regulated in the US, or are engine exhaust emissions still a more pressing concern, if at all? Let us know what you think in the comments below.