Health risk assessment of emerging PFOS substitute 8:2 Cl-PFESA: evidence from mouse spermatogenesis and derivation of a safe exposure threshold

The global decline in total fertility rate has been linked to environmental contaminants like per- and polyfluoroalkyl substances (PFASs), yet the male reproductive toxicity and health risks of the widely detected emerging substitute, 8:2 chlorinated polyfluorinated ether sulfonate (8:2 Cl-PFESA), remain poorly understood. This study aimed to investigate the testicular toxicity of 8:2 Cl-PFESA (0.04, 0.2, 1.0 mg/kg for 12 weeks) in male mice. Dose-dependent testicular damage was observed, manifested as seminiferous tubule disarray, reduced serum testosterone levels, and sperm abnormalities. Integrated omics analysis highlighted the sphingolipid signaling pathway as a core pathway, which was validated through the disruption of stress fibers and downregulation of F-actin expression. Benchmark dose modeling predicted a BMDL₁₀ of 0.023 mg/kg/day and a CRfD of 4.577 ng/kg/day, indicating a higher sensitivity of 8:2 Cl-PFESA compared to PFOS. Risk assessment indicated potential non-carcinogenic risks (HQ = 1.60, MOE = 0.59) for highly exposed occupational populations, while carcinogenic risk remained below the concern threshold (CR = 1.39 × 10^-7). By innovatively coupling mechanism-driven multi-omics discovery with quantitative, health-based threshold derivation (CRfD) and probabilistic risk metrics (HQ, MOE), this study establishes a predictive and evidence-based assessment framework. This approach moves beyond traditional hazard identification to enable sensitive, early-warning risk characterization for emerging contaminants prior to widespread human exposure, thereby providing a critical scientific basis for proactive chemical regulation and preventing regrettable substitution.