Abstract-Perfluorooctane sulfonic acid (PFOS) accumulates in the liver and blood of exposed organisms. The potential for these surfactant molecules to interfere with hormone/protein interactions in blood is of concern given the importance of these interactions. The PFOS binding to serum proteins was investigated by assessing its ability to displace a variety of steroid hormones from specific binding proteins in the serum of birds and fishes. Perfluorooctane sulfonic acid had only a weak ability to displace estrogen or testosterone from carp serum steroid binding proteins. Displacement of cortisone in avian sera occurred at relatively low PFOS concentrations. Corticosterone displacement potency increased with chain length, and sulfonic acids were more potent than carboxylic acids. The PFOS concentrations estimated to cause these effects were 320 M or greater, equivalent to serum concentrations greater than 160 mg/L. Using mass spectrometry and direct in vitro binding assays, PFOS was demonstrated to bind strongly to bovine serum albumin (BSA) in a 1:1 stoichiometric ratio. It appears that PFOS in serum is in general bound to albumins. Concentrations of PFOS required to saturate albumin would be in excess of 50 to 100 mg/L. Based on current environmental concentrations, it is unlikely that PFOS would cause displacement of hormones from serum proteins in wildlife.

The photodynamic, actue toxicities of 20 polycyclic aromatic hydrocarbons (PAHs) to Duphniu mugnu were predicted by photophysical and physiochemical parameters. The photophysical parameters considered were lowest singlet energy, lowest triplet energy, singlet-triplet splitting energy and phosphorescence lifetime. The physiochemical parameters were first-and second-order connectivity indices and log P values. D. magna were exposed to aqueous solutions of each PAH such that equimolar concentrations in D. mugnu were achieved. The organisms and the PAHs were then exposed to 120 pW/cm2 UV-A and 25 pW/cm2 UV-B light. Mortality times (min) were recorded and the results reported as median lethal time (LT50). Potency factors (+) were calculated and used to rank the PAHs in terms of relative photodynamic toxicity. Some statistically relevant correlations between individual physical parameters and toxicity were observed. Linear, multiple regression models were poor predictors of photoinduced PAH toxicity. A curve-linear model was developed to predict photoinduced toxicity from triplet energy. Goodness-of-fit chi-square tests were performed and demonstrated that triplet energy was an effective predictor both of observed LT5O and of LT50 values adjusted to a constant PAH concentration. Toxicity data were also analyzed using discriminant functional analysis. A stepwise, canonical correlation parameter selection method separated the PAHs into three toxic categories by using triplet energy and phosphorescence lifetime as variables. This model, which classifies PAHs as very toxic, moderately toxic or nontoxic, was 100% accurate when the model developed from one set of PAHs was tested with a different set.

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Toxicity reference values (TRVs) and predicted no effect concentrations (PNECs) were derived for perfluorooctane sulfonate (PFOS) based on the characteristics of a top avian predator. On the basis of the protective assumptions used in this assessment, the benchmarks are protective of avian populations and were based on acute and chronic dietary exposures of northern bobwhite quail and mallard. Toxicological endpoints included mortality, growth, feed consumption, and histopathology. Reproductive endpoints included egg production, fertility, hatchability and survival, and growth of offspring. On the basis of the U. S. Environmental Protection Agency Great Lakes Initiative methodology, and a lowest observable adverse effect concentration (LOAEC) of 10 mg PFOS kg(-1) feed, an uncertainty factor of 36 was derived. The TRV based on PFOS dietary intake was 0.021 mg PFOS kg(-1) body weight day(-1), while for serum, liver, and egg, TRVs were 1.7 microg PFOS mL(-1), 0.6 microg PFOS g(-1) wet weight, and 1.7 microg PFOS mL(-1), respectively. On the basis of the European Commission methodology, a correction factor of 2 (for lowest observed effect level to no observable effect level) and an assessment factor of 30, for a total adjustment of 60, were used to derive PNECs. PNECs based on dietary, mean serum, liver, and egg PFOS concentrations were 0.013 mg PFOS kg(-1) body weight day(-1), 1.0 microg PFOS mL(-1), 0.35 microg PFOS g(-1) wet weight, and 1.0 microg PFOS mL(-1), respectively.

Per-and poly-fluoroalkyl substances (PFAS) encompass a large, heterogenous group of chemicals of potential concern to human health and the environment. Based on information for a few relatively well understood PFAS such as perfluorooctane sulfonate and perfluorooctanoate, there is ample basis to suspect that at least a subset can be considered persistent, bioaccumulative, and/or toxic. However, data suitable for determining risks in either prospective or retrospective assessments are lacking for the majority of PFAS. In August 2019, the Society of Environmental Toxicology and Chemistry sponsored a workshop that focused on the state-of-the-science supporting risk assessment of PFAS. This paper summarizes discussions concerning ecotoxicology and ecological risks of PFAS. First, we summarize currently available information relevant to problem formulation/prioritization, exposure, and hazard/effects of PFAS in the context of regulatory and ecological risk assessment activities from around the world. We then describe critical gaps and uncertainties relative to ecological risk assessments for PFAS and propose approaches to address these needs. Recommendations include the development of more comprehensive monitoring programs to support exposure assessment, an emphasis on research to support the formulation of predictive models for bioaccumulation, and the development of in silico, in vitro, and in vivo methods to efficiently assess biological effects for potentially sensitive species/endpoints. Addressing needs associated with assessing the ecological risk of PFAS will require cross-disciplinary approaches that employ both conventional and new methods in an integrated, resource-effective manner.

Mink and otters are good integrators of their aquatic environments and useful sentinel species for determining exposure to environmental contaminants. In this study, perfluorooctanesulfonate (PFOS; C8F17SO3-), perfluorooctanesulfonamide (FOSA; C8F17SO2NH2), perfluorohexanesulfonate (PFHxS; C6F13SO3-), and perfluorooctanoate (PFOA; C7F15CO2-) were measured in livers of mink and river otters collected from various locations in the United States. PFOS was found in all mink livers analyzed. Frequencies of occurrence of FOSA, PFHxS, and PFOA were less. The greatest concentration of PFOS measured in liver of mink was 5140 ng/g, wet weight. Maximum concentrations of FOSA, PFHxS, and PFOA in mink livers were 590, 39, and 27 ng/g, wet weight, respectively. There were no significant positive relationships between concentrations of PFOS and PFHxS or PFOA in mink livers. Concentrations of PFOS were positively correlated with those of FOSA in mink livers from Illinois. There was no significant correlation between concentrations of PFOS and lipid content in mink livers. There were no age- or sex-related differences in the concentrations of fluorochemicals in mink livers. Greater concentrations are associated with those individuals collected near urbanized and/or industrialized areas. PFOS was detected in livers of all river otters collected from Washington and Oregon at concentrations ranging from 25 to 994 ng/g, wet wt.

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