Analysis of Ultra Short-Chain PFAS in Urine: Method Development by LC-MS/MS and First Human Biomonitoring Results from the German National Cohort (NAKO)

Ultra short-chain perfluoroalkyl substances (USC PFAS) with C1-C3 chain lengths are increasingly important. Globally, trifluoroacetic acid (TFA) makes up the largest proportion of PFAS in the environment, however, knowledge about human internal exposure to these substances is scarce. We present a new, fast and robust human biomonitoring (HBM) method to quantify simultaneously 5 USC PFAS in urine. A simple dilute and shoot method based on liquid chromatography-tandem mass spectrometry using isotope dilution was developed, validated and applied in a HBM pilot study using samples from a population-based subsample of the general population. It showed linearity up to 75 µg/L, low limits of quantification (LOQ 0.05–1.5 μg/L), satisfactory matrix spiked mean relative recoveries (95–107 %) and overall precision (VC 2.9–12 %). In an initial set of two longitudinal samples from 150 participants, aged 21–69 years, of the German National Cohort Hamburg study center, TFA was detected in all samples, ranging from 2.96 to 1512 µg/L. Trifluoromethanesulfonic acid (TFMS) was detected in 73 % and quantified in 8 % of samples, providing first evidence of its occurrence in urine. All other analytes were below LOQ in all samples. Adjusted linear regression analyses showed that baseline TFA levels increased across five age groups and year of examination. From baseline (2015–2019) to follow-up (2020–2024) median of TFA increased on average by 1.6-fold, independent of aging. These are the first longitudinal data on TFA internal exposure among adults from a German metropolitan region, revealing the need for analyzing potential predictors of exposure over time.