A Review of Road Traffic-Derived Non-Exhaust Particles: Emissions, Physicochemical Characteristics, Health Risks, and Mitigation Measures

Implementation of regulatory standards has reduced exhaust emissionsof particulate matter from road traffic substantially in the developed world. However,nonexhaust particle emissions arising from the wear of brakes, tires, and the roadsurface, together with the resuspension of road dust, are unregulated and exceedexhaust emissions in many jurisdictions. While knowledge of the sources ofnonexhaust particles is fairly good, source-specific measurements of airborneconcentrations are few, and studies of the toxicology and epidemiology do not givea clear picture of the health risk posed. This paper reviews the current state ofknowledge, with a strong focus on health-related research, highlighting areas wherefurther research is an essential prerequisite for developing focused policy responses tononexhaust particles.