Ecotoxicological Risk Assessment of Anionic Surfactants, an Underestimated Pollutant: A Case Study in Mexican Lotic Waters.

Abstract

Anionic surfactants are widely used in domestic and industrial products and are commonly discharged into aquatic environments due to inadequate wastewater treatment, particularly in developing countries. This study evaluated the ecological risk of Linear Alkylbenzene Sulfonate (LAS) in Mexican lotic systems using data from the National Water Quality Measurement Network collected between 2019 and 2024. Measured environmental concentrations were compared with a predicted no-effect concentration of 0.08723 mg/L derived from a species sensitivity distribution model and with a value established by the Mexican state for the protection of aquatic life: Freshwater, 0.1 mg/L. Ecological risk was characterized using risk quotients (RQs), which identified sites with unacceptable risk (RQs ≥ 1). Spatial analyses revealed persistent multi-year hotspots, suggesting semi-continuous discharges and limited contaminant removal. Key uncertainties include reliance on acute toxicity data, Interferences associated with the MBAS method, and limited information for native tropical species. These findings emphasize the need to strengthen wastewater treatment policies (in low and middle-income countries) and expand chronic toxicity assessments using native aquatic species.