Whole Blood with Unlabeled and Labeled PFAS Standards Spiked onto Dried Blood Spot Cards Analyzed using a 6546 Mass Spectrometer

A small subset of per- and polyfluoroalkyl substances (PFAS) are routinely screened in human blood. These compounds generally explain less than 50% of the total PFAS in human blood, estimated based on organic fluorine. Furthermore, the percentage of known PFAS in human blood has been decreasing as replacement PFAS and more complex PFAS chemistries are introduced to the market. Most of these novel PFAS have not been previous identified. Non-targeted methods are required to characterize this “dark matter” PFAS. The objective of this study was to apply non-targeted PFAS analysis to human blood to gain an understanding about the sources, concentrations, and toxicity of these compounds. A state-of-the-art high resolution tandem mass spectrometry and software workflow for PFAS characterization in dried blood spots is reported. Dried blood spots are a less invasive collection technique compared to venous blood draws, allowing collection from vulnerable populations. Large biorepositories of archived dried blood spots are available internationally from newborns and present opportunities to study prenatal exposure to PFAS. In this study, pooled human whole blood was dried on blood spot cards and analyzed using iterative MS/MS on an Agilent 6546 LC/Q-TOF. Blinded data processing was conducted using FluoroMatch Suite including a recently developed visualizer tool that presents homologous series, retention time vs m/z plots, MS/MS spectra, feature tables, annotations, and fragments for fragment screening. This workflow was able to annotate 95% (20/21) of standards  spiked on dried blood spot samples, signifying a low false negative rate using FluoroMatch Suite. A total of 28 PFAS (20 standards, 4 standard contaminants, and 4 additional endogenous compounds) were detected across  five homologous series with Schymanski Level 2 confidence: fluorotelomer perfluoroalkyl sulfonic acids (FTS), perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl ether carboxylic acids (PFECAs), perfluoroalkyl sulfonic acids (PFSAs), and perfluoroalkyl ether sulfonic acids (PFESAs). 93 additional potential PFAS were further detected using fragments screening. PFAS are extremely persistent and widespread yet remain largely unregulated. Our findings will contribute to an improved understanding of exposures. Application of these methods in environmental epidemiology studies have the potential to inform policy with regards to PFAS monitoring/ regulation and individual-level mitigation strategies.