Environmental occurrence, fate, impact, and potential solution of tire microplastics: Similarities and differences with tire wear particles

Highlights: • Tire microplastics (TMPs) include tire wear particles and other types. • Litte is known for recycled tire crumb and tire repair-polished debris. • Different analytical methods of TMPs were assessed and compared. • Environmental behavior, toxicity, and risk of TMPs were discussed. • Future studies should focus on environmentally relevant TMPs. Tire microplastics (TMPs) are identified as one of the most abundant types of microplastics, which originate from rubber with intended or unintended release. While increasing knowledge about TMPs concentrates on tire wear particles (TWPs), TMPs from other potential sources like recycled tire crumb (RTC) and tire repair-polished debris (TRD) are much less understood. Excessive levels of TMPs and their additives have been fragmentarily reported in the environment. The accumulating environmental TMPs from different sources may directly or indirectly cause adverse impacts on the environment and human health. The objectives of this review are to (1) summarize the properties, abundance, and sources of TMPs in the environment; (2) analyze the environmental fates and behaviors of TMPs, including their roles in carrying abiotic and biotic co-contaminants; (3) evaluate the potential impacts of TMPs on terrestrial and aquatic organisms, as well as human; and (4) discuss the potential solutions to mitigate the TMP pollution. By collecting and analyzing the up-to-date literature, this review enhances our better understanding of the environmental occurrence, fates, impacts, and potential solutions of TMPs, and further highlights critical knowledge gaps and future research directions that require cooperative efforts of scientists, policymakers, and public educators.