Biological effects of Tire and Road Wear Particles (TRWP) assessed by in vitro and in vivo studies – A systematic review

Air quality is a critical issue because even small amounts of air pollutants can cause significant adverse health effects. Road traffic is a major contributor to air pollution both through aerosols from exhaust emissions (EE) and non-exhaust emissions (NEE). The latter result from mechanical abrasion of brakes and tires, erosion of road surfaces and resuspension of road dust into the atmosphere by passing traffic. EE have been extensively characterized and have declined over time due to mitigation measures. By contrast, NEE have been less studied, are not tightly regulated and there are limited data on their toxicity. Thus, NEE relative part has become prevalent, potentially making of these emissions a major human health concern. The aim of this systematic review was to provide an overview of the current state of knowledge on the biological effects of NEE. We paid particular attention to the toxicological effects of Tire and Road Wear Particles (TRWP) induced in vitro and in vivo in mammalian models. To this end, we performed a bibliographic search in two databases (PubMed and Web of Science). Of the 400 papers, 22 were found to be relevant and included in our analysis, confirming that the assessment of the TRWP toxicity in mammalian models is still limited. This review also reports that oxidative stress and inflammation are the main mechanisms underlying the toxicity of TRWP.