Human health risk assessment of Tire and Road Wear Particles (TRWP) in air

Abstract

This risk assessment addresses potential human health impact of exposure to tire and road wear particles (TRWP), which are formed at the interface of the pavement and road comprising rubber with embedded mineral from the pavement. To conduct the risk assessment, we reviewed literature on hazards associated with and exposures to TRWP and developed a screening value for TRWP reliant on the available hazard data and appropriate dosimetric adjustments. The species- and time- adjusted no-observed-adverse-effect-concentration (NOAEC) for respirable TRWP was 55 µg/m3. This NOAEC was compared to exposure estimates for respirable TRWP for both typical and worst case exposure scenarios based on age-specific activity patterns to determine the margin of exposure for TRWP. The estimated daily exposure to TRWP ranged from 0.079 to 0.147 µg/m3, resulting in a margin of exposure for TRWP ranging from approximately 400 to 700. Though there remain uncertainties in the risk assessment stemming from both the hazard and exposure assessments, the current weight of evidence suggests that TRWP presents a low risk to human health.