Brake-Wear Particle Emissions - An Emerging Challenge

Today non-exhaust particulate matter emissions, the abrasion of brakes, tires and the road itself, as well as resuspension of road dust, already have a significant share of up to 86% of all road traffic emissions. The UNECE's Particle Measurement Program is currently elaborating a planned test procedure for the regulation of brake-wear particle emissions. This paper covers the latest state of knowledge of brake wear emissions discussing their origins, physical properties and health effects. Further insights into the challenges in sampling, detection and characterization that need to be addressed to allow for a standardized, robust and reproducible brake-wear particle measurement, are given. Finally, the methodology is reviewed with respect of its potential to represent real-world emission behavior and the potential and challenges for on-board measurements.