Elevated Reproductive Risk and Toxicity of Triclosan in Urban Freshwater Environments after the COVID- 19 Pandemic

Abstract

Triclosan (TCS) is widely used in personal care products due to its effective antibacterial properties. However, the increasing frequency of TCS detection in global surface waters, particularly following the heightened use of disinfectants during the COVID- 19 pandemic, underscored the need for careful environmental risk assessment. In this study, we conducted ecological toxicity assays using the model organism Caenorhabditis elegans to investigate the potential risks of environmentally relevant concentrations of TCS. After 72 h of exposure, specific reproductive toxicity, including a decrease in eggs in utero at concentrations ranging from 0.1 to 5 μg L⁻¹ was observed. The predicted no-effect concentration (PNEC) was determined based on a 10% inhibition of egg formation using the Hill and Weibull models. At lower concentrations, TCS inhibited total brood size in C. elegans and increased intracellular ROS levels and sod- 3 antioxidant gene expression. The reproductive risk of TCS in urban freshwater environments was further assessed using predicted environmental concentrations (PEC) from 2019 to 2022 and the PNEC simulated in this study. Risk quotient (RQ) and exceedance risk (ER) analyses indicated a high reproductive risk of TCS (RQ > 1 or inhibition > 10% at ER = 0.5) in urban rivers and lakes, particularly in the post-pandemic period. Given the global concern over the potential hazards of TCS, our findings contributed to understanding its environmental risks in urban freshwater systems and provided a basis for regulatory authorities to develop appropriate control measures and management strategies.