Tire wear particles impact a roadside wild plant species.

Road traffic is a fundamental component of modern human society. Recently, tire wear particles, generated by road traffic through friction between tires and road surfaces, have been increasingly recognized as toxic to a wide range of organisms. While previous studies have examined impacts on aquatic ecosystems or edible plants (i.e., crops), the effects of tire wear particles on urban green spaces, such as parks and roadside vegetation belts located close to roads, have remained largely unexplored. Here, we conducted a tire wear particle exposure experiment using Bromus catharticus, a common roadside weed species in Japan. Our results demonstrated tire wear particles significantly inhibited both shoot and root growth. In addition, the particles significantly elevated oxidative stress, assessed by malondialdehyde (MDA) content, in roots. These findings show the potential for widespread impacts of tire wear particle contamination in urban green ecosystems.