Integrating BAF-BCF Disparities into Species Sensitivity Distributions to Refine Water Quality Criteria: A...

Disparities between the bioaccumulation factor (BAF) and bioconcentration factor (BCF) can cause laboratory-based water quality criteria (WQC) to deviate from the levels needed to protect organisms in actual environmental conditions, yet this issue has not been adequately addressed in current frameworks. To fill this gap, we compiled 2769 records of per- and polyfluoroalkyl substances (PFAS) spanning two decades and conducted a meta-analysis. The analysis systematically evaluated BAF-BCF disparities and their patterns, identified key drivers, and explored integrating them into species sensitivity distribution (SSD) models to refine WQC. Results showed that BCF were consistently lower than BAF for most PFAS, with disparities increasing with carbon chain length and octanol-water partition coefficient. Further analysis indicated that exposure concentration and trophic level were primary drivers, with concentration effects dominated by endowment effects and trophic effects by coefficient effects. Endowment effects were fixed within a mixed-effects model, and a trophic level-specific BAF/BCF ratio driven by coefficient effects was constructed. This ratio was then incorporated into the SSD framework to refine WQC, resulting in 2.5-fold and 3.2-4.4-fold reductions for PFOA and PFOS, respectively. This study provides the first systematic assessment of PFAS BAF-BCF disparities and integrates them into SSD-based WQC derivation, offering a practical pathway toward more accurate and ecologically relevant WQC for bioaccumulative contaminants.