Comparative Toxicity of Seven Aqueous Film-Forming Foam to In Vitro Systems and Mus

The comparative toxicity of six per- and polyfluoroalkyl substance (PFAS)-free and one PFAS-containing aqueous film-forming foam (AFFF) was evaluated in an outbred mouse species as well as several in vitro assays. The in vivo toxicological profile of PFAS-free AFFFs in short-term, high-concentration exposures is different than that of a PFAS-containing AFFF. The PFAS-containing reference product induced increased liver weights, while the PFAS-free AFFFs were linked to either decreased or unaffected relative liver weights. The in vitro toxicological profile across PFAS-free AFFFs was uniform except in the Microtox® assay, where thresholds were variable and spanned several orders of magnitude. This direct comparison of products through short-term toxicity tests and in vitro screenings represents early data to support evaluation of potential regrettable substitutions when selecting alternative PFAS-free AFFFs. Further work in diverse taxa (e.g., aquatic organisms, terrestrial invertebrates, birds) and mammalian studies capturing sensitive life stages will refine and expand this data set across a range of risk-relevant toxicological endpoints. Environ Toxicol Chem 2023;42:2364-2374. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

Reproductive and immune effects emerge at similar thresholds of PFHxS in deer mice

Although perfluorohexane sulfonate (PFHxS) is structurally similar to perfluorooctane sulfonate (PFOS) and also widely detected in humans and the environment, comparatively fewer toxicity data exists on this 6-chain perfluoroalkyl sulfonic acid. In this study, repeated oral doses of PFHxS were administered to deer mice (Peromyscus maniculatus) to evaluate subchronic toxicity and potential effects on reproduction and development. Maternal oral exposure to PFHxS caused increased stillbirths, which is relevant for ecological risk assessment, and resulted in a benchmark dose lower limit (BMDL) of 5.72 mg/kg-d PFHxS. Decreased plaque formation, which is relevant for human health risk assessment, occurred in both sexes of adult animals (BMDL = 8.79 mg/kg-d PFHxS). These data are the first to suggest a direct link between PFHxS and decreased functional immunity in an animal model. Additionally, female animals exhibited increased liver:body weight and animals of both sexes exhibited decreased serum thyroxine (T4) levels. Notably, since reproductive effects were used to support 2016 draft health advisories and immune effects were used in 2022 drinking water health advisories released by the United States Environmental Protection Agency for PFOS and perfluorooctanoic acid (PFOA), these novel data can potentially support advisories for PFHxS because relevant points of departure emerge at similar thresholds in a wild mammal and corroborate the general understanding of per- and polyfluoroalkyl substances (PFAS).

Next-generation PFAS 6:2 fluorotelomer sulfonate reduces plaque formation in exposed white-footed mice

6:2 fluorotelomer sulfonate (6:2 FTS) has been used as a replacement for legacy per- and polyfluoroalkyl substances (PFAS). We assessed reproductive and developmental effects in a human-wildlife hybrid animal model based on the association of adverse effects linked to legacy PFAS with these sensitive life stages. In this study, white-footed mice were exposed orally to 0, 0.2, 1, 5, or 25 mg/kg-day 6:2 FTS for 112 days (4 weeks premating exposure plus at least 4 weeks mating exposure). Pregnancy and fertility indices were calculated, and litter production, total litter size, live litter size, stillbirths, litter loss, average pup weight, and pinna unfolding were assessed. Sex steroid and thyroid hormone serum levels were assessed. Body weight, histopathology, and immune function were also assessed in this study. Reproductive endpoints were not significantly altered in response to 6:2 FTS. Spleen weight increased in male mice dosed with 6:2 FTS. Immune function determined via a plaque-forming cell (PFC) assay was decreased in both male and female mice in the 2 highest doses. A low benchmark dose was calculated based on PFCs as the critical effect and was found to be 2.63 and 2.26 mg/kg-day 6:2 FTS in male and female mice, respectively. This study characterizes 6:2 FTS as being potentially immunotoxic with little evidence of effect on reproduction and development; furthermore, it models acceptable levels of exposure. These 2 pieces of information together will aid regulators in setting environmental exposure limits for this PFAS currently thought to be less toxic than other PFAS.

Reproductive and developmental toxicity of perfluorooctane sulfonate (PFOS) in the white-footed mouse (Peromyscus leucopus)

Concerns about per- and polyfluoroalkyl substances (PFAS) stem from their ubiquitous presence in the environment, bioaccumulation, resistance to degradation, and toxicity. Previously, toxicity data relevant to ecological risk assessment has largely been aquatic, terrestrial invertebrates, or avian in origin. In this study, repeated oral exposures of perfluorooctane sulfonate (PFOS) were administered to white-footed mice (Peromyscus leucopus) to evaluate effects on reproduction and development. Prenatal exposure to high doses of PFOS caused neonatal mortality, though growth and development were unaffected by low doses. Additionally, parental (P) generation animals exhibited increased liver:body weight, increased hepatocyte cytoplasmic vacuolization, and decreased serum thyroxine (T4) levels. Total litter loss was selected as the protective critical effect in this study resulting in a benchmark dose low (BMDL) of 0.12 mg/kg-d PFOS. Importantly, PFOS exposure has been linked to reduced adult recruitment in myriad species and at similar thresholds to this study. Similarities in critical/toxicologic effects across taxa may add confidence in risk assessments at sites with multiple taxa or environments.

Patterns in Serum Toxicokinetics in Peromyscus Exposed to Per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) are compounds manufactured for use in paints, cleaning agents, fire suppressants, nonstick cookware, food containers, and water-resistant products. Concerns about PFAS stem from their ubiquitous presence in the environment, persistence, and variable/uncertain bioaccumulation and toxicity. In the present study, 5 perfluoroalkyl acids and one polyfluoroalkyl substance were administered to white-footed mice (Peromyscus leucopus) to elucidate the kinetics of each chemical over 28 d of exposure. Perfluorooctanoate, perfluorohexane sulfonate (PFHxS), and perfluorobutane sulfonate were administered to male and female mice via drinking water. Perfluorooctane sulfonate, perfluorononanoate, 6:2 fluorotelomer sulfonate, and PFHxS were administered to male and female mice via oral gavage. Blood samples collected after 14 or 21 and 28 d of exposure were analyzed for individual PFAS concentrations via liquid chromatography-tandem mass spectrometry. In general, a plateau in serum concentration in this toxicity test-relevant timeline depended on interactions between 1) the type of PFAS (i.e., perfluoroalkyl sulfonic acids [PFSAs] vs perfluoroalkyl carboxylic acids [PFCAs] vs polyfluorinated), 2) continuous versus bolus dosing, and 3) to a lesser extent, sex. Specifically, PFCAs were detected at higher concentration in females than males, whereas PFSAs were generally detected at similar levels across sex. An exception occurred when PFHxS yielded higher serum levels in males than females through bolus, but not continuous, dosing. Type of PFAS had the largest impact on serum concentrations, whereas sex had the lowest. As such, future work on the toxicokinetics of PFAS in common ecological receptors would be valuable to further explore these patterns. Environ Toxicol Chem 2021;40:2886-2898. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Assessing the Impacts of Methoxychlor Exposure on the Viability, Reproduction, and Locomotor Behavior of the Seminole Ramshorn Snail (Planorbella duryi)

In the present study, the effects of short-term methoxychlor exposure on the viability, reproduction, and locomotor behavior of adult seminole ramshorn snails (Planorbella duryi) was assessed. To examine impacts on viability and behavior, individuals were exposed to a water control, vehicle control, or 12.5, 50, 100, 250, 500, or 1000 μg/L of methoxychlor for 48 h; and differences in mortality and locomotor behavior assessed using the freely available ToxTrac software. To determine impacts on reproduction, pairs of snails were exposed to a vehicle control and 12.5, 25, 50, 100, and 250 μg/L of methoxychlor for 9 d; and the number of clutches and eggs laid quantified every 24 h. Methoxychlor concentrations in treatments were determined using gas chromatography. Complete mortality was observed in the 500 μg/L and 1000 μg/L treatments after 48 h and in the 250 μg/L treatment after 9 d. Decreases in the number of egg clutches were observed in all treatments, and the number of eggs laid decreased starting in the 25 μg/L treatment. Decreases in average speed, mobile speed, and total distance traveled, as well as a significant increase in frozen events, were also observed. Our results suggest that methoxychlor exposure causes detrimental effects on several nonlethal endpoints in a nonmodel aquatic invertebrate species and that the analysis of locomotor behaviors serves as a reliable, sensitive endpoint for ecotoxicology testing. Environ Toxicol Chem 2019;39:220-228. © 2019 SETAC.

Differential expression of hepatic genes with embryonic exposure to an environmentally relevant PCB mixture in Japanese quail (Coturnix japonica)

The upper Hudson River was contaminated with polychlorinated biphenyls (PCB) Aroclor mixtures from the 1940s until the late 1970s. Several well-established biomarkers, such as induction of hepatic cytochrome P450 monooxygenases, were used to measure exposure to PCBs and similar contaminants in birds. In the present study, Japanese quail eggs were injected with a PCB mixture based upon a congener profile found in spotted sandpiper eggs at the upper Hudson River and subsequently, RNA was extracted from hatchling liver tissue for hybridization to a customized chicken cDNA microarray. Nominal concentrations of the mixture used for microarray hybridization were 0, 6, 12, or 49 μg/g egg. Hepatic gene expression profiles were analyzed using cluster and pathway analyses. Results showed potentially useful biomarkers of both exposure and effect attributed to PCB mixture. Biorag and Ingenuity Pathway Analysis® analyses revealed differentially expressed genes including those involved in glycolysis, xenobiotic metabolism, replication, protein degradation, and tumor regulation. These genes included cytochrome P450 1A5 (CYP1A5), cytochrome b5 (CYB5), NADH-cytochrome b5 reductase, glutathione S-transferase (GSTA), fructose bisphosphate aldolase (ALDOB), glycogen phosphorylase, carbonic anhydrase, and DNA topoisomerase II. CYP1A5, CYB5, GSTA, and ALDOB were chosen for quantitative real-time polymerase chain reaction confirmation, as these genes exhibited a clear dose response on the array. Data demonstrated that an initial transcriptional profile associated with an environmentally relevant PCB mixture in Japanese quail occurred.