Road-runoff pollution in English surface drains: Chemical composition and potential associated environmental risk(s)

Rivers and other surface waters worldwide receive thousands of chemicals from diverse sources, including road runoff. We identified more than 170 chemicals that have been associated with road runoff across the published literature that derive from tire wear, exhaust emissions, and brake pad abrasion, among other sources. However, the impact of these chemicals on aquatic organisms is poorly understood. Addressing this knowledge gap for United Kingdom (UK) surface drains, we first analyzed the available literature studies on road runoff (23) to determine the concentrations of 70 chemicals in road runoff monitored in surface drains by the U.K. Environment Agency over 25 years (between 2000 and 2024). We showed that 43 of the 70 monitored chemicals in U.K. surface drains exceeded reported minimum concentrations and 19 exceeded the highest measured concentrations across the existing literature. Twenty of the monitored chemicals exceeded the lowest effect concentration for 50% lethality in fish and/or aquatic invertebrates. These findings suggest that road-runoff chemicals in U.K. surface drains pose a potential risk to aquatic life, but their impacts will depend on other factors including their dilution levels in rivers.