Wear Particle Emissions of Brake Systems—A Scoping Review

As electromobility reduces tailpipe emissions, regulatory focus, including the upcoming Euro-7 standard, shifts to non-exhaust emissions (NEEs). Brake wear particulate matter (PM) significantly contributes to urban pollution and severe health risks. This Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) for Scoping Reviews (ScRs) compliantly reviews systematically mapped research on brake dust generation, measurement methodologies, and mitigation strategies. Following a literature search across Scopus, Web of Science, and EBSCOhost for English and German publications, 125 studies were extracted using the AI tool Elicit and manually verified. The synthesis indicates that coarse particles (PM10 and PM2.5) originate primarily from mechanical abrasion and tribo-oxidation, while ultrafine particles (UFPs) form via thermal decomposition of organic binders at critical temperature thresholds. For quantification, enclosed inertia dynamometers with constant volume sampling (CVS) show clear convergence as the standard. Effective mitigation includes wear-resistant hard coatings, low-emission pad formulations, active on-board filtration, and enclosed drum or encapsulated wet brakes. Furthermore, regenerative braking in electric vehicles (EVs) can reduce particulate emissions by up to 95% under standardized driving cycles or optimal operating conditions. Despite these advancements, knowledge gaps remain. Future research must prioritize standardizing real-world on-road measurement protocols, enabling wet braking concepts for automotive applications by addressing drag losses and performance limits, and developing and validating coupled predictive models as a basis for future digital twins to design zero-emission braking architectures.