Fluorine mass balance, precursor transformability, and screening-level inhalation prioritization of PFAS-containing...

Ten PFAS-containing firefighting foam concentrates from South Korea were characterized by LC-MS/MS target analysis, IMS-HRMS suspect screening with CCS-supported confidence assignment, the total oxidizable precursor (TOP) assay, total organofluorine (TOF) analysis, and screening-level inhalation prioritization. PFOS and PFOA were not detected, whereas C6 fluorotelomer-derived PFAS dominated all eight AFFF-related products. 6:2 FTAB accounted for 97.5-98.6% of quantified PFAS in five products and 6:2 FTS for 92.3-96.3% in the remaining three. Suspect screening identified 16 PFAS classes, including four candidate classes previously unreported in firefighting foams. TOP results indicated unknown oxidizable PFCA precursor pools. Apparent target-plus-suspect fluorine recovery averaged 45 ± 52% across all ten products, including LOQ-bound estimates for two SS products without directly quantifiable TOF, indicating unresolved organofluorine. Under a conservative indoor scenario without self-contained breathing apparatus (SCBA) protection, the toxicity reference value (TRV)-normalized hazard index (HI) was dominated by 6:2 FTS and reached 18.1 for H-AFFF at 450 L/min. Although 6:2 FTAB had the largest target-PFAS burden, it was excluded from the main HI because only an exploratory 28-day oral provisional TRV was available; therefore, the HI should be interpreted as a screening-level prioritization metric rather than a definitive inhalation risk estimate.