Tire crumb in the environment: a review on occurrence, fate and recent advances in detection and analysis

Tire wear particles (TWPs) are increasingly recognised as a contaminant of emerging concern, owing to their toxic and omnipresent nature. Given these characteristics, it is imperative to discuss their occurrence and fate across different environmental matrices and critically examine the current state-of-the-art technologies utilised for their sampling, detection and analysis. This review provides a comprehensive overview of the physicochemical characteristics of TWPs, their occurrence, environmental fate, and detection methodologies. It further investigates the dominant methodological bottlenecks in the detection and quantification of TWPs across different environmental matrices, highlighting key challenges in their atmospheric and waterborne cycling, including inconsistent emission estimates, a lack of standardised protocols, and a limited understanding of transport and transformation processes. Our findings revealed that TWPs are ubiquitous across all environmental matrices; however, their transport and transformation remain poorly constrained due to variable density, aggregation, ageing and additive leaching behaviour, all of which complicate modelling efforts. In addition, we also concluded that despite rapid progress in spectroscopic, thermal and mass-based approaches, there remains no standardised, matrix-independent method potent enough for achieving simultaneous chemical specificity, particle-scale resolution, and quantitative recovery. Such findings emphasise the urgent need for harmonised analytical workflows and integrative studies linking physicochemical properties to environmental mobility and toxicity. This review thus establishes a conceptual framework for bridging analytical advances with environmental process understanding, an essential step towards reliable risk evaluation of tire-derived microplastics. It further offers essential insights to researchers, policymakers, and environmental professionals determined to better comprehend and alleviate the effects of tire wear particles on ecosystems and human health.