Making waves: Addressing the over-conservatism of the assessment factor method in aquatic ecological risk assessment

The assessment factor (AF) method remains the most widely used method for deriving predicted no-effect concentrations (PNEC) in aquatic ecological risk assessment (ERA), particularly for emerging contaminants (ECs). However, the inherent conservatism of the AF method may result in the systematic overestimation of ecological risks. This study critically evaluates PNEC derivation for sulfamethoxazole and other representative ECs. The findings reveal that studies identifying these pollutants as posing high ecological risks consistently relied on AF-derived PNEC values, which were typically 2-3 orders of magnitude lower than those obtained using the species sensitivity distribution (SSD) method. Bibliometric analysis further indicates that these conservative PNEC have been extensively adopted and cited, potentially shaping regulatory decisions and environmental management practices. To address this issue, we propose methodological advancements, including standardized toxicity data screening protocols, simplified derivation methods, adaptive assessment factor schemes, and the creation of an open, dynamically updated global PNEC database. These innovations aim to improve the scientific accuracy of ERA, mitigate regulatory overprotection, and optimize resource allocation in environmental management.