A review on rubber tire originated micro- and nano-plastics: fate, impact and risks

Micro- and nano-plastics generated by friction- and traction-induced wear and tear of rubber tires, designated as TMPs and TNPs, are a major source of air, terrestrial, and aquatic contamination. These particles are dispersed from the point of generation to distant locations via wind action, and storm water and wastewater discharges, adding to the particulate matter load in ambient air, and resulting in river and marine flora and fauna contamination. The occurrence of TMPs and TNPs in the environment is widespread, persistent and unregulated. This paper critically assesses the current scientific knowledge on TMPs and TNPs by conducting a systematic review and focusing on their occurrence, methods of identification and characterization, and knowledge gaps related to their fate, transport, and environmental impacts. Their fate primarily depends on the particles’ size, shape, density, composition, and possible interactions with living organisms and plants, along with processes like fragmentation, aggregation, sorption, and bioaccumulation. These particles also have the potential to leach heavy metals and aromatic hydrocarbons, causing detrimental impacts on aquatic and terrestrial organisms, including physical damage, physiological disruption, and bioaccumulation, depending on exposure levels, duration, and the type of interaction. The lack of standardized methodologies for the identification, quantification, and characterization of TMPs and TNPs poses a significant challenge in terms of wider environmental risk assessment, while their sources, emissions, transport, and impacts remain highly uncertain.