Environmental risk assessment of paracetamol in aquatic ecosystems using species sensitivity distribution and global occurrence data

Paracetamol is one of the most widely consumed pharmaceutical compounds globally, yet its environmental and human health impacts remain poorly characterized. This study provides a comprehensive environmental risk assessment of paracetamol by combining Species Sensitivity Distribution (SSD) modeling with global occurrence data. A total of 55 EC₁₀ values from aquatic species were collected to define the related SSD, resulting in a hazard concentration affecting the 5 % of the population (HC₅) of 0.05 mg/L and a predicted no-effect concentration (PNEC) of 0.01 mg/L. Paracetamol concentrations were compiled from multiple environmental compartments, including wastewater treatment plant (WWTP) influents and effluents, hospital and industrial discharges, surface waters, groundwater, and drinking water, across five continents. Risk Quotients (RQs) revealed extremely high ecological risks in influents (up to RQ > 800) and notable risks in surface and treated waters in countries with limited wastewater infrastructure. A preliminary human health risk assessment based on drinking water data was also performed to estimate Chronic Daily Intake (CDI) and Hazard Quotients (HQs) for adults and children. HQ values were consistently higher in children, but remained below the safety threshold (HQ < 1) across all scenarios. The findings underscore both the environmental persistence of paracetamol and the importance of strengthening monitoring efforts, especially in regions with elevated exposure. The study also highlights the need to consider cumulative effects from pharmaceutical mixtures and account for age-specific vulnerability in future risk assessments. Overall, this work provides a robust, global perspective on the risks posed by paracetamol and offers actionable insights for regulatory and public health interventions.