Brake Emissions: The Next Hot Environmental Issue?

Theodoros Grigoratos has been studying brake-related emissions since 2013. He’s a leading expert, but he’s quick to point out that the field is still struggling with incomplete information and a lack of standardized testing.

At the SAE Brake Colloquium in October, he gave a presentation titled “Brake Emissions — A Global Challenge.” It outlined what experts know and the next steps required to obtain a better understanding of the issue.

One point of emphasis: Engine emissions are dramatically lower than they used to be. Non-exhaust emissions, meanwhile, are holding steady. That inevitably will bring more attention to issues like tire wear and brake wear, as these emissions make up a larger portion of overall vehicle emissions than in the past.

Grigoratos works with the United Nations Economic Commission for Europe Particle Measurement Programme (UN PMP). He cites two other organizations, JASIC in Japan and the California Air Resources Board, as also leading the effort to get a handle on the issue.

He stresses the need for solid scientific answers to the big question: How damaging are these emissions? Collaboration is required, since the issue involves medical research, knowledge of air dynamics, better testing of emissions, and the study of overall ambient air quality. In his SAE Brake Colloquium presentation, Grigoratos noted that “at the moment, the information we can provide health experts on brake emissions appears vague.”

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The biggest obstacle to building high-quality data “seems to be the lack of a standardized method for measuring brake particle emissions,” Grigoratos says. “Each researcher applies their own method and as a result incomparable or even contrasting results are published.” In addition, much of the testing fails to replicate real-world conditions.

Grigoratos is confident that this obstacle is surmountable. Agencies are working together to create standard testing methods, and a recently published paper suggested an effective way to measure brake particulate matter.

The BRAKE Report spoke with Grigoratos about his research:

TBR: Asbestos is used a lot less often than it used to be. Copper and other heavy metals are being phased out. So what are the biggest remaining problems with brake-related PM?

TG: Without a doubt there have been several steps towards the right direction. However, there are still several aspects that need to be addressed. First of all, the actual overall amount of brake particles released in the atmosphere shall be investigated. Then it is the size of these particles, which in some cases fall in the nanoparticles range (i.e. 10-30 nm) that raise concerns. Additionally, not much is known with regard to the organic constituents of the brake pads. Finally, possible adverse health effects need to be investigated.

TBR: Speaking subjectively, if someone asks you, “How big of a problem is brake-related PM,” what would you say?

TG: We miss fundamental information to answer this question. First of all, we need to assess the contribution of brake emissions to the ambient air PM concentrations. Published studies are either out of date or based on not very accurate source apportionment methodologies. I believe that when the ongoing PMP project is finalized we will be in the position to provide more accurate emission factors and answer this question.

Last but not least we should not forget future technologies. There are projections showing that a significant amount of real-world brake applications will be covered by regenerative braking in EVs. This topic should be further investigated as it will completely change the brake system design, thus affecting brake wear emissions.

We miss fundamental information to answer this question.

TBR: What are some next steps that you would like to see?

TG: Brake emissions have a global character. There are strong ongoing activities in Europe, US and Japan. However, there are big challenges that a single group cannot address alone. In PMP we have managed to approach the topic by involving stakeholders from all around the world. We would like to see more key players joining our common efforts and we would also like decision makers to continue enabling this joint global approach.

Earlier in The BRAKE Report: Where lightweighting and brakes intersect

Ben Nussbaum
Ben Nussbaum

Ben Nussbaum, Chief Content Officer of The Brake Report, has more than 20 years experience in publishing. He was the founding editor for USA Today's line of special interest magazines and the founding editor for i5 Publishing's newsstand one-off magazine program. He lives outside Washington, D.C. Email him at [email protected].