Toxicity of Tire Particles Released from Personal Mobilities (Bicycles, Cars, and Electric Scooters) on Soil Organisms

Tire particles are generated by the abrasion of treads in tires on roads, and are major contributors of microplastics in soil environments. Tire wear particle contamination worsened when the use of personal mobilities increased in relation to the Covid-19 pandemic. In this study, tire particles (112–541 μm) were obtained from three types of personal mobility tires (bicycles, cars, and electric scooters) and exposed to plants ( Vigna radiata ) and springtails ( Folsomia candida ) for 28 d to assess the toxicity of each tire particle type. The tire particles exhibit adverse effects depending on the origin of the tire or test species. Particles from bicycle or electric scooter tires decreased the bulk density and inhibited the water holding capacity of the soil and plant growth (shoots and leaves). Car tire particles had detrimental effects on springtails (growth inhibition and decreased reproduction rate). We concluded that tire particles can affect the soil environment by changing soil properties; thus, causing adverse effects in soil organisms. Our findings could be the basis for the currently limited research on tire particles in soil environments and the toxicity of environmentally relevant microplastics.