Analytical challenges and possibilities for the quantification of tire-road wear particles

As one of the largest sources of microplastic particle emissions, tire-road wear particle mixtures (TRWPs) pose a potentially high threat to various environmental compartments. Their heterogenous properties, from varying particle size, density, shape, texture, elemental and chemical composition, cause challenging analytical workflows. Current analytical methods for TRWP can be summarized in two main groups: single-particle-based and bulk-based methods. Both groups include a large variation of methods, with different demands for sampling and sample pre-treatment, and different possible outputs. This review provides an overview of the current analytical methods used for TRWP studies and in particularly quantifications, with focus on methods that have been peer-reviewed and tested for environmental samples. The review presents current possibilities and limitations with the different analytical approaches, as well as highlighting gaps in the current TRWP knowledge and information needed to move this research field forward.