B-294 PFAS combinations identified in more than 10,000 human serum/plasma samples

Background PFAS are endocrine disrupting chemicals that can have additive effects. Thousands of perfluoroalkyl substances (PFAS) have been synthesized for various applications over several decades. They are widely used in industrial and commercial applications due to their excellent surfactant properties, hydrophobicity, lipophobicity, and chemical and thermal stabilities. Their persistence and wide distribution in the environment mean that humans experience ongoing exposure. One concern is that PFAS exposure is associated with numerous health effects including, but not limited to certain cancers, dyslipidemia, and developmental and reproductive issues. Identification of the PFAS combinations found in human samples can help inform research efforts about the mixtures that should be included in comprehensive additive-effect studies. The objective of this study was to determine the combination of PFAS observed in a large population of human serum/plasma samples. Methods The testing laboratory receives serum and plasma samples from across the United States for PFAS testing. Special handling instructions include avoiding sample collection devices coated with PTFE/Teflon® and polyvinylidene fluoride. Rejection criteria include submission of sample in a polymer gel separation tube. Instrumental analysis was performed on a Sciex API 4500 QTrap triple quadrupole mass spectrometer with electrospray ionization (ESI+). The LLOQ (lower limits of quantification) for each PFAS were 0.1 ng/mL. Demographic information such as sex, age, occupation, and geographic location is limited as it not always provided with the sample. Exposure histories are also unknown. Two PFAS test panels were selected for this study. The first test panel (Panel 1) includes 13 PFAS and was selected because it had the most test orders while the second test panel (Panel 2) was selected because it was the most comprehensive (18 PFAS). The data presented in this study is derived from samples received between DEC 2023 and DEC 2024. Comparable data evaluations were performed for both panels. Results A total of 58 different PFAS combinations were identified. The most common PFAS combination observed in both panels (n=2736 from Panel 1 and n=18 from Panel 2) included PFHxS, linear PFOA, linear and branched PFOS, PFNA and PFHpS. The greatest number of PFAS (n=10) were found in 11 samples. The figure shows the PFAS combinations and frequencies found in more than 10 samples analyzed using Panel 1. Conclusion It is known that PFAS are not equivalent regarding half-life or ability to produce an adverse health event. Additive effects have also been reported. This means that to best study overall effects, it is relevant to evaluate PFAS in combinations. The testing of more than 10,000 samples for PFAS, affords a valuable opportunity to report on the frequency of PFAS combinations found in humans. This work demonstrates many combinations of PFAS were observed in the samples tested with a large number of individuals attaining a body burden of at least 5 or more PFAS. It also provides a template that researchers studying PFAS additive effects in humans can follow to help ensure their work is representative of PFAS combinations found in authentic samples.