Prediction of freshwater ecotoxicological hazardous concentrations of major surfactants using the QSAR-ICE-SSD method

Abstract

Synthetic surfactant products are continuously released into the aquatic environment in large quantities, posing a burden on ecosystems as a "pseudo-persistent" organic pollutant. Threshold derivation for protecting aquatic ecosystems is challenging due to the various homologous components of surfactants. In this study, five commercially available products were chosen as representative major types of surfactants. Corresponding quantitative structure-activity relationships (QSAR) were screened and subsequently combined with interspecific correlation estimation (ICE) to develop species sensitivity distributions (SSDs) for each component. Then, the 5th percentile hazard concentrations (HC₅s) were calculated. The results indicated that the developed QSAR-ICE models demonstrated good toxicity prediction performance. The HC₅ of each component showed a negatively correlation with alkyl chain length and a positive correlation with the amount of ethylene oxide. The HC₅s of surfactants correlate with variations in their charged properties. Quaternary ammonium compounds (QAC) exhibited the lowest HC₅s (8.5 ± 18.3 μg/L), followed by alcohol ethoxylates (AE), linear alkylbenzene sulfonates (LAS), and alcohol ethoxylated sulfates (AES); and alkyl oxide (AO) exhibited the highest HC₅s (15784.2 ± 21552.6 μg/L). For cationic surfactants, the HC₅s in the invertebrates were significantly lower than those in the fish; conversely, for anionic surfactants, the opposite was true, indicating a difference in the toxic mechanisms of surfactants with different charged properties across species taxa. Additionally, among invertebrates, shellfish demonstrated heightened sensitivity to surfactants, owing to their high accumulation and low metabolism of pollutants. Salmoniformes were the most sensitive among all species, indicating the necessity of prioritizing these species for aquatic ecological conservation in surfactant-contaminated waters.

Keywords: Aquatic toxicity; Hazardous concentration; Interspecies correlation estimations; Quantitative structure–activity relationship; Species sensitivity distribution; Surfactants.