Abstract
Per- and polyfluoroalkyl substances (PFAS) are a class of chemicals that were widely used in manufacturing and are now present in the environment throughout the world. It is known that various PFAS are quantifiable in human in blood, but potential adverse health outcomes remain unclear. Sentinel and non-traditional model species are useful to study potential toxicity of PFAS in order to understand the relationship between environmental and human health. Here, we present a critical review of studies on the neurotoxicity of PFAS in sentinel and non-traditional laboratory model systems, including Caenorhabditis elegans (nematode), Dugesia japonica (planarian), Rana pipiens (frogs), Danio rerio and Oryzias melastigma (fish), and Ursus maritimus (polar bears). PFAS have been implicated in developmental neurotoxicity in non-traditional and traditional model systems as well as sentinel species, including effects on neurotransmitter levels, especially acetylcholine and its metabolism. However, further research on the mechanisms of toxicity needs to be conducted to determine if these chemicals are affecting organisms in a similar manner. Overall, findings tend to be similar among the various species, but bioaccumulation may vary, which needs to be taken into account in future studies by quantifying target organ concentrations of PFAS to better compare different species. Furthermore, data on the majority of PFAS is lacking in neurotoxicity testing, and additional studies are needed to corroborate findings thus far.
Highlights
Per- and polyfluoroalkyl substances (PFAS) are chemicals that have been used in industry since around the 1950s [1,2]
The longer chain PFAS, with 7 or more carbons were first phased out of the United States in 2001 due to findings of toxicity; they are still prevalent in the environment due to their strong carbon–fluorine bonds, which makes them extremely stable and persistent, and because they are still used in other parts of the world and can be shipped to the United States (Figure 1) [1,2]
Glutathione synthase activity was positively correlated with levels of perflourooctane sulfonate (PFOS), total perfluorosulfonates, and perfluoroundecanoate (PFUnDA) and borderline correlated to levels of perfluorododecanoate (PFDoDA), perfluorotetradecanoate (PFTrDA), and total perfluorocarboxylates in the occipital lobe, and positively correlated with PFOS and total perfluorosulfonates in the frontal cortex while being negatively correlated with total perfluorosulfonates in the hypothalamus (Table 3) [52]
Summary
Per- and polyfluoroalkyl substances (PFAS) are chemicals that have been used in industry since around the 1950s [1,2]. This is especially general, far more data are needed to definitively show that shorter chain PFAS accumulate less than highlighted by evidence of shorter chain (6 carbon) PFAS with long half lives, such as perfluorohexane longer chain PFAS This is especially highlighted by evidence of shorter chain (6 carbon) PFAS with sulfonate, PFHxS (>5 years) [7]. These compounds still are not metabolized, are prominent long half lives, such as perfluorohexane sulfonate, PFHxS (>5 years) [7] These in water, including that for drinking, and have largely unknown toxicological effects [1,4]. Studies in model systems such as Cymologous monkeys, rats, and mice have indicated various forms of toxicity; the shorter half-lives of PFAS in rodents requires a large exposure to obtain internal doses similar to those in humans. There is still much to understand about the potential neurotoxicity of PFAS
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