Risk assessment of bisphenol A and its analogues via breast milk within a select population of lactating women in South Korea: A multi-method approach for reducing exposure assessment uncertainty.

Bisphenol A (BPA) and its structural analogues-bisphenol F (BPF) and bisphenol S (BPS)-are ubiquitous environmental contaminants of concern for breastfed infants due to their high intake per body weight and vulnerable developmental windows. This study evaluated bisphenol exposure via breast milk in Korean infants using three complementary methodological approaches-deterministic, probabilistic, and individualized assessment-to reduce assessment uncertainty. Breast milk samples from 203 Korean lactating mothers were analyzed for BPA, BPF, and BPS using validated LC-MS/MS methods. EDIs were calculated using deterministic assessment, probabilistic Monte Carlo simulation with 10,000 iterations, and individualized pair-level assessment. Detection frequencies were 39% for BPA, 26% for BPF, and 28% for BPS, with geometric mean concentrations of 0.101, 0.127, and 0.070 μg/L, respectively. Median EDIs ranged from 5.37 to 11.61 ng/kg bw/day across the three bisphenols. Risk characterization varied substantially depending on selected international HbGV. Sensitivity analysis revealed that bisphenol concentration contributed 65-82% of exposure variability, followed by milk intake (15-30%). Individualized assessment identified high-risk subgroups with BPS exposures exceeding 1000 ng/kg bw/day. The multi-method assessment framework effectively reduces exposure assessment uncertainty and reveals how methodological choices influence risk characterization. Because BPF and BPS were detected almost as frequently as BPA, yet neither compound has a compound-specific health-based guidance value in any jurisdiction, an expedited regulatory review of the BPA substitutes-rather than a continued exclusive focus on BPA-is required if the current market substitution is not to reproduce, in the most vulnerable population, the very risk that restricting BPA was intended to remove.