The rapid screening of protein binding affinity for poly- and perfluoroalkyl substances (PFAS) benefits risk assessment and fate and transport modelling. PFAS are known to bioaccumulate in livestock through contaminated food and water. One excretion pathway is through milk, which may be facilitated by binding to milk proteins such as bovine serum albumin (BSA). We report a label-free differential scanning fluorimetry approach to determine PFAS–BSA binding over a broad temperature range. This method utilizes the tryptophan residue within the protein binding pocket as an intrinsic fluorophore, eliminating the need for fluorophore labels that may influence binding. BSA association constants were determined by (a) an equilibrium-based model at the melting temperature of BSA and (b) the Hill adsorption model to account for temperature dependent binding and binding cooperativity. Differences in binding between PFAS and fatty acid analogs revealed that a combination of size and hydrophobicity drives PFAS binding.
A sensitive method for the detection of legacy and emerging per- and polyfluorinated alkyl substances (PFAS) in dairy milk
There is widespread contamination by per- and polyfluoroalkyl substances (PFAS) across the globe, with adverse effects on human and environmental health. For human exposure, drinking water and dietary exposure have been recognized as important PFAS exposure pathway for the general population. Several documented cases of dairy milk contamination by PFAS have raised concerns over this exposure pathway in general. A sensitive method for determination of 27 PFAS in milk was hence modified and applied on raw and processed milk samples from 13 farms across the United States (U.S.). A combination of acid and basic extraction method and ENVI-Carb clean-up achieved recoveries of targeted PFAS between 70 and 141%. The method detection limits (MDL) ranged from 0.8 to 22 ng/L (for 26 PFAS) and 144 ng/L for perfluorobutanoic acid (PFBA). The uniqueness of this method is considered in the targeted screening of a broad range of legacy PFAS, as well as perfluorinated sulfonamide species and fluorotelomer sulfonates. No legacy PFAS were detected in 13 milk samples from regions of concern given local use of biosolids or proximity to fire training areas. Overall, then, the uptake of perfluoroalkyl acids (PFAA) from dairy milk in the U.S. is considered low.
Probing the Interactions of Perfluorocarboxylic Acids of Various Chain Lengths with Human Serum Albumin: Calorimetric and Spectroscopic Investigations
Abstract. Despite an exponential increase in PFAS research over the past two decades, the mechanisms behind how PFAS cause adverse health effects are still
Species-Specific Unbound Fraction Differences in Highly Bound PFAS: A Comparative Study across Human, Rat, and Mouse Plasma and Albumin
Per- and polyfluoroalkyl substances (PFAS) are a diverse group of fluorinated compounds which have yet to undergo comprehensive investigation regarding potential adverse health effects and bioaccumulative properties. With long half-lives and accumulative properties, PFAS have been linked to several toxic effects in both non-clinical species such as rat and mouse as well as human. Although biological impacts and specific protein binding of PFAS have been examined, there is no study focusing on the species-specific fraction unbound (fu) in plasma and related toxicokinetics. Herein, a presaturation equilibrium dialysis method was used to measure and validate the binding of 14 individual PFAS with carbon chains containing 4 to 12 perfluorinated carbon atoms and several functional head-groups to albumin and plasma of mouse (C57BL/6 and CD-1), rat, and human. Equivalence testing between each species-matrix combination showed positive correlation between rat and human when comparing fu in plasma and binding to albumin. Similar trends in binding were also observed for mouse plasma and albumin. Relatively high Spearman correlations for all combinations indicate high concordance of PFAS binding regardless of matrix. Physiochemical properties of PFAS such as molecular weight, chain length, and lipophilicity were found to have important roles in plasma protein binding of PFAS.
Binding of Per- and Polyfluoroalkyl Substances (PFAS) to Serum Proteins: Implications for Toxicokinetics in Humans
Abstract. Per- and polyfluoroalkyl substances (PFAS) are a diverse class of highly persistent anthropogenic chemicals that are detectable in the serum of m
Estimated exposure to perfluoroalkyl substances during infancy and serum-adipokine concentrations in later childhood
Perfluoroalkyl substances (PFASs) are transferred through human milk and may cause elevated exposure during infancy. Given the lack of early postnatal blood samples, PFAS concentrations can be estimated to serve as predictors of subsequent metabolic toxicity.
Addressing Urgent Questions for PFAS in the 21st Century
Abstract. Despite decades of research on per- and polyfluoroalkyl substances (PFAS), fundamental obstacles remain to addressing worldwide contamination by
A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects
Here, we review present understanding of sources and trends in human exposure to poly- and perfluoroalkyl substances (PFASs) and epidemiologic evidence for impacts on cancer, immune function, metabolic outcomes, and neurodevelopment. More than 4000 PFASs have been manufactured by humans and hundreds have been detected in environmental samples. Direct exposures due to use in products can be quickly phased out by shifts in chemical production but exposures driven by PFAS accumulation in the ocean and marine food chains and contamination of groundwater persist over long timescales. Serum concentrations of legacy PFASs in humans are declining globally but total exposures to newer PFASs and precursor compounds have not been well characterized. Human exposures to legacy PFASs from seafood and drinking water are stable or increasing in many regions, suggesting observed declines reflect phase-outs in legacy PFAS use in consumer products. Many regions globally are continuing to discover PFAS contaminated sites from aqueous film forming foam (AFFF) use, particularly next to airports and military bases. Exposures from food packaging and indoor environments are uncertain due to a rapidly changing chemical landscape where legacy PFASs have been replaced by diverse precursors and custom molecules that are difficult to detect. Multiple studies find significant associations between PFAS exposure and adverse immune outcomes in children. Dyslipidemia is the strongest metabolic outcome associated with PFAS exposure. Evidence for cancer is limited to manufacturing locations with extremely high exposures and insufficient data are available to characterize impacts of PFAS exposures on neurodevelopment. Preliminary evidence suggests significant health effects associated with exposures to emerging PFASs. Lessons learned from legacy PFASs indicate that limited data should not be used as a justification to delay risk mitigation actions for replacement PFASs.
Can profiles of poly- and Perfluoroalkyl substances (PFASs) in human serum provide information on major exposure sources?
Humans are exposed to poly- and perfluoroalkyl substances (PFASs) from diverse sources and this has been associated with negative health impacts. Advances in analytical methods have enabled routine detection of more than 15 PFASs in human sera, allowing better profiling of PFAS exposures. The composition of PFASs in human sera reflects the complexity of exposure sources but source identification can be confounded by differences in toxicokinetics affecting uptake, distribution, and elimination. Common PFASs, such as perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) and their precursors are ubiquitous in multiple exposure sources. However, their composition varies among sources, which may impact associated adverse health effects.
Stability of Per- and Polyfluoroalkyl Substances in Solvents Relevant to Environmental and Toxicological Analysis
Abstract. Per- and polyfluoroalkyl substances (PFASs) are widely used anthropogenic chemicals. For environmental and toxicological analysis, it is importan
Are Fluoropolymers Really of Low Concern for Human and Environmental Health and Separate from Other PFAS?
Abstract. Fluoropolymers are a group of polymers within the class of per- and polyfluoroalkyl substances (PFAS). The objective of this analysis is to evalu
A Liquid–Liquid Extraction Method for Measuring Ultrashort PFCAs and Longer-Chain PFAS in Water
Abstract. Natural waters can contain diverse per- and polyfluoroalkyl substances (PFAS) with contrasting chemistries, presenting challenges for using a sin
How Do We Measure Poly- and Perfluoroalkyl Substances (PFASs) at the Surface of Consumer Products?
Abstract. Exposures to poly- and perfluoroalkyl substances (PFASs) have been linked to metabolic disruption, immunotoxicity, and cancer in humans. PFASs ar
PFAS Exposure Pathways for Humans and Wildlife: A Synthesis of Current Knowledge and Key Gaps in Understanding
Abstract. We synthesize current understanding of the magnitudes and methods for assessing human and wildlife exposures to poly‐ and perfluoroalkyl substanc
Development and Evaluation of Aquatic and Terrestrial Food Web Bioaccumulation Models for Per- and Polyfluoroalkyl Substances
Abstract. There is a need for reliable models to predict the food web bioaccumulation and assess ecological and human health risks of per- and polyfluoroal
Calibration of Perfluorinated Alkyl Acid Uptake Rates by a Tube Passive Sampler in Water
Abstract. Per- and polyfluoroalkyl substances (PFAS) are a group of 4000+ man-made compounds of great concern due to their environmental ubiquity and adver
Machine learning-enhanced identification of fluorophilic interactions for improved SERS detection of PFOA
Per- and polyfluoroalkyl substances (PFASs), such as the legacy C8 compound perfluorooctanoic acid (PFOA), pose significant environmental and health risks due to their persistence and widespread use. , Per- and polyfluoroalkyl substances (PFASs), such as the legacy C8 compound perfluorooctanoic acid (PFOA), pose significant environmental and health risks due to their persistence and widespread use. While surface-enhanced Raman spectroscopy (SERS) has shown promise for PFAS detection, challenges remain in achieving high sensitivity and understanding the underlying molecular interactions. This study combines fluorinated thiol-modified SERS substrates with machine learning techniques to enhance PFOA detection and elucidate fluorophilic interactions. Three different fluorinated thiols were used to modify SERS substrates, and their performance in PFOA detection was compared to bare substrates. Surface modification improved SERS signal enhancement and lowered detection limits compared to unmodified surfaces. Machine learning algorithms, including partial least squares-discriminant analysis (PLS-DA), partial least squares regression (PLSR), and support vector machine (SVM) regression, were employed to classify and quantify PFOA based on Raman spectral features. The PLS-DA model successfully distinguished ligand-specific interaction patterns, demonstrating strong robustness and predictive performance, while SVM regression achieved a limit of detection of 3.61 ppb. We further validated the proposed machine learning-guided SERS approach for PFOA detection directly in water, demonstrating ligand-specific Raman responses arising from fluorophilic ligand–PFOA interactions. A linear and sensitive response was observed at environmentally relevant concentrations, confirming the practical applicability of the approach for aqueous PFAS monitoring. This approach offers a novel SERS-based strategy for detecting PFOA, with results anticipated to inform future developments in applying this strategy to a broader range of PFAS compounds and more complex environmental matrices.