Unveiling novel and legacy PFAS in human hair

A recent approach for human biomonitoring of per- and polyfluoroalkyl substances (PFAS) is non-invasive human hair sampling. In this study, solid-phase extraction (SPE), liquid-chromatography and tandem mass spectrometry (UPLC-MS/MS) were used to measure an extended set of PFAS in human hair. 45 hair samples from German voluntary subjects (19 female, 26 male) were screened for 26 target compounds, including perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs), fluorotelomer sulfonic acids (FTSAs), fluorotelomer carboxylic acids (FTCAs), fluorotelomer unsaturated carboxylic acids (FTUCAs), polyfluoroalkyl phosphate diesters (diPAPs), perfluorooctanesulfonamide (FOSA), N-ethyl perfluorooctane sulfonamidoacetic acid (N-EtFOSAA) and bis(trifluoromethane)sulfonimide (NTf2). 22 out of 26 target analytes were detected with two to 16 PFAS per sample. The most frequently detected substances were 6:2 FTSA, PFOS, PFOA and 6:2 diPAP with detection frequencies (Df) of 93, 87, 84, and 78 %, respectively. The emerging ionic liquid ingredient NTf2 was found in 44 % of all samples, which points to its widespread occurrence. To the best of our knowledge, NTf2 has been detected for the first time in human hair. The PFAS sum concentrations per subject ranged from 121 pg/g to 10332 pg/g. Maximum concentrations were found for PFOS (3763 pg/g), 6:2 FTSA (3600 pg/g) and PFPeS (3154 pg/g). Young subjects <30 years showed significantly higher levels for the ∑_PFAS (median 2231 pg/g) and the ∑_PFSAs (median 735 pg/g) compared to subjects >30 years (median ∑_PFAS 1196 pg/g, and for ∑_PFSAs 453 pg/g). This study demonstrates that in addition to the generally monitored PFCAs and PFSAs further precursors like diPAPs, FTSAs, and their transformation products considerably contribute to the total PFAS pattern in hair. This reflects the PFAS exposure of humans, even if blood-hair transfer factors are not yet established for PFAS and subject selection was not representative for the whole German population.