Youn Jeong Choi

A wide range of per- and polyfluoroalkyl substances (PFAS) have been found in human serum and linked to adverse human health effects. The current increase in ultrashort-chain PFAS levels in the environment has led to a significant increase in detection and reporting of ultrashort chain PFAS in human samples. However, studies on the potential background contamination of ultrashort chains from manufacturing processes or non- essential additives are limited compared to legacy PFAS. This study tested various blood collection tubes used for human blood sampling for ultrashort chain PFAS background contamination including TFA (trifluoroacetic acid). Findings showed TFA concentrations in multiple tubes at 11.5-53.7 ng per tube while concentrations of other PFAS were insignificant. TFA was found at particularly high rates in tubes containing separator gel. TFA was consistently detected in blood samples collected using tubes containing TFA. Previous studies have used a plethora of tubes without concern for PFAS contamination, thus potentially affecting results and interpretation. This study informs future researchers in better blood collection tubes when studies focus on evaluating PFAS bioaccumulation and impacts on human health.

Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants that readily interact with proteins, yet their interactive behavior with human hemoglobin (Hb) remains poorly understood despite its essential role in oxygen transport. We combined molecular modeling, equilibrium dialysis, and spectroscopic analyses to characterize the interactions of 11 structurally diverse PFAS with human Hb and evaluate whether binary PFAS mixtures exhibit additive or non-additive effects. Computational docking and molecular dynamics simulations ranked PFAS according to their predicted ability to perturb Hb structure, and these predictions were validated experimentally using equilibrium dialysis measurements of PFAS partitioning to Hb and fluorescence and UV-visible spectroscopy. Long-chain PFAS, particularly perfluorononanoic acid (PFNA), consistently exhibited the greatest interaction with Hb across computational and experimental approaches. Equilibrium dialysis showed increasing partition coefficients with increasing perfluoro carbon chain length, while fluorescence and absorbance analyses revealed concentration-dependent alterations in Hb conformation and local microenvironment. PFNA produced the largest fluorescence response and the clearest dose-dependent effects, whereas most short-chain PFAS and GenX elicited minimal structural perturbations. Binary mixture experiments with PFNA and PFOS demonstrated fluorescence responses that exceeded predicted additive effects at higher concentrations, indicating concentration-dependent synergistic interactions. Collectively, these findings demonstrate that PFAS structure strongly influences Hb interactions and conformational perturbation, that integrated computational approaches can successfully predict relative interactive behavior, and that PFAS mixtures can produce effects that are not readily predicted from single-compound exposures. This integrated framework provides a mechanistic basis for improving predictions of PFAS-protein interactions and supports more realistic evaluations of PFAS mixture toxicity.

Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants of emerging concern in the Laurentian Great Lakes, yet pathways of their transfer through aquatic food webs remain poorly understood. Chironomid midges, which are abundant in Lake Erie sediments and a key food source for fish and birds, may facilitate the transfer of PFAS from benthic sediments to higher trophic levels in aquatic and terrestrial ecosystems. We assessed the presence and concentrations of a suite of PFAS in surface water, sediment, and chironomid larvae collected from the Central Basin of Lake Erie and assessed whether concentrations change with increasing distance from shore. Sediment exhibited the highest total PFAS concentrations (mean ± SE = 88.93 ± 41.21 ng/g d.w.), with PFOS being the dominant compound. Water samples had a total PFAS concentration of 19.42 ± 3.55 ng/L, dominated by PFOA and PFOS. In contrast, chironomid larvae had comparatively low total PFAS body burdens (0.55 ± 0.13 ng/g d.w.), and like sediment, were dominated by PFOS. Biota-sediment accumulation factors (BSAFs) for midges were low (0.01 ± 0.007) PFAS concentrations in water, sediment, and midges varied with distance from shore, with inshore and midshore locations showing higher concentrations than offshore locations. Multivariate analysis revealed that PFAS profiles differed between water and sediment and that water profiles differed with distance from shore. Our findings demonstrate that chironomids in Lake Erie contain detectable PFOS concentrations, although at substantially lower levels than nearby sediments. However, their high abundance and ecological importance as prey suggest they may contribute to PFAS transfer between benthic, pelagic, and nearshore terrestrial food webs.

Aquatic organisms may be exposed to multiple concurrent stressors, including anthropogenic contaminants and alterations to abiotic parameters such as temperature and conductivity. Amid global climate change, elucidating the interactions between chemical and environmental factors is a priority. In recent years, per- and polyfluoroalkyl substances (PFAS) have emerged as contaminants of global concern owing to their persistence, bioaccumulation potential, and toxicity. While limited studies have documented the influence of temperature and conductivity on PFAS bioaccumulation in fish, the underlying physiological drivers associated with changes to uptake and elimination remain poorly understood. Therefore, the present study aimed to determine the influence of temperature and conductivity on metabolic parameters and bioconcentration of an environmentally relevant PFAS mixture in bluegill, Lepomis macrochirus . Fish were exposed to a mixture of perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid (PFOA), and perfluorohexanoic acid (PFHxA) at 20 and 25 °C and conductivity levels of 300, 600, and 1200 µS/cm for a 32-day uptake and 32-day depuration period. Additionally, we measured individual resting metabolic rate (RMR), maximum metabolic rate (MMR), and aerobic scope under the same temperature and conductivity conditions. Overall, PFOS and PFHxS accumulation in the liver were consistently higher in fish at 20 °C compared to 25 °C, which was linked to more rapid contaminant elimination at higher temperatures. Resting and maximum metabolic rates increased with temperature, independent of conductivity. These results will facilitate the development of robust bioaccumulation models to enhance predictive modeling of PFAS accumulation and aid in understanding the physiological drivers of fish contaminant accumulation.

Perfluorooctanesulfonate (PFOS), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnA) are three legacy long-chain per-/polyfluoroalkyl substances (PFAS). Although phased out of production, recent studies indicate substantial exposure can occur through consumption of contaminated freshwater fish, with minimal information known on the potential for developmental toxicity, especially for PFDA and PFUnA. In this study, zebrafish were used to characterize the toxicokinetics of these three PFAS as a model for developmental neurotoxicity, specifically behavior and dopamine (DA) dysregulation. Mass spectrometer quantification of water and tissue samples revealed that all three PFAS were rapidly absorbed during the early developmental window and bioconcentrated in tissue to a substantial degree. The visual motor response assay revealed altered behavioral patterns in the larvae, especially for PFDA and PFUnA. Enzyme-linked immunosorbent assay (ELISA) quantification of DA indicated these compounds induced elevations in total DA at nearly every exposure concentration for each compound down to the lowest test concentration used in this study at 0.004 ppb (ppb, μg/L) (equivalent to 4 ppb, US EPA drinking water regulation for PFOS). These findings confirm that PFOS, PFDA, and PFUnA exhibit a substantial capacity for bioaccumulation and demonstrate a need for further research into how developmental exposure impacts neurological health.

Amid global concern regarding the health and environmental impacts of per- and polyfluoroalkyl substances (PFAS), there is an urgent need to develop and implement alternative products without PFAS. Consequently, PFAS-free firefighting foams used for fire suppression have been developed for use in military and residential settings. To facilitate the selection of lower-risk PFAS-free foams, the present study focused on the chronic toxicity of seven PFAS-free and one PFAS-containing foam to six aquatic species. Target species included two cladocerans, Daphnia magna and Ceriodaphnia dubia; the chironomid Chironomus dilutus; the mysid Americamysis bahia; and two fish species, Pimephales promelas and Cyprinodon variegatus, with endpoints including growth, development, reproduction, and survival. To facilitate comparison and product toxicity rankings, effective concentrations (20%, 50%) and no- and lowest-observed-effect concentrations (NOECs and LOECs, respectively) were calculated. Effective concentrations, NOECs, and LOECs varied by over an order of magnitude among foams and species, with several of the PFAS-free formulations ranked as highly toxic based on US Environmental Protection Agency alternatives assessment hazard criteria. Overall, the PFAS-free foams were found to exhibit either similar or greater toxicity compared to the PFAS-containing reference foam across several species and endpoints. Nonmonotonic and hormetic dose responses were observed in D. magna for several of the tested foams, with increased reproduction and growth at intermediate exposures. Generally, tested foam toxicity rankings were consistent with a related acute toxicity study using the same species and formulations, and other research using soil invertebrates. Combined with related efforts for other taxa including mammals, birds, and plants, the present research will facilitate the selection of appropriate PFAS-free firefighting foams that minimize harm to the environment. Environ Toxicol Chem 2024;43:2436–2454. © 2024 SETAC