Developing AquaticLife Criteria for BenzalkoniumChlorides Based on QSAR-ICE-SSD Prediction and Ecological Risk Assessment

Benzalkonium chlorides (BACs) are emerging prevalent antimicrobial chemicals in aquatic ecosystems, but there is limited research on their aquatic toxicity and the development of aquatic life criteria (ALC), hindering ecological risk assessments and regulatory policies. To address this knowledge gap, we studied three predominant BAC homologues: BAC-C12, BAC-C14, and BAC-C16. These compounds are widely used in industrial applications and are frequently detected in surface waters, making them a priority for aquatic toxicity assessment and ALC development. A novel approach integrating quantitative structure–activity relationship (QSAR) and interspecies correlation estimation (ICE) models was developed to predict aquatic toxicity, validated with an experimental test. The expanded toxicity data set, including predicted and measured values, was used to develop species sensitivity distribution (SSD) models for deriving ALC. The criterion maximum concentrations (CMC) were determined to be 7.04, 6.66, and 5.72 μg/L for BAC-C12, BAC-C14, and BAC-C16, respectively, while criterion continuous concentrations (CCC) were 1.18, 1.11, and 0.95 μg/L for BAC-C12, BAC-C14, and BAC-C16, respectively. Ecological risk assessment based on data from previous literature revealed that BAC-C12 and BAC-C14 pose a non-negligible risk to aquatic ecosystems in the investigated countries, underlining the need for further monitoring and regulatory action.