Doctor of Philosophy (PhD)
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Francisco Alberto Fernandez Lima
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Per- and polyfluoroalkyl substances (PFASs) are a group of synthetic surfactants that have utilized for several decades in a wide range of industrial and manufacturing applications. Owing to their high chemical stability, PFAS are widespread and persistent in the environment, and have been shown to be bioaccumulative in diverse organisms including plants, wildlife, and humans. Exposure to PFASs has been linked to a range of documented toxic and/or adverse effects in relation to human and animal health. The potential environmental health and ecotoxicity of next-generation PFAS remain unclear. In the present study, toxicity, and bioconcentration potential, of several perfluoroether carboxylic acids (PFECA), as emerging pollutants of concern, in early life stages of marine (Mahi-Mahi and Olive Flounder) and freshwater fish (zebrafish) was assessed. Toxicity including lethality, behavioral and developmental effects of PFECA, and the legacy PFAS, perfluorooctanoic acid (PFOA), was assessed in embryonic stages of zebrafish, alongside high-resolution magic angle spin nuclear magnetic resonance (HRMAS NMR) metabolomics techniques to elucidate metabolic pathways affected by PFAS. These studies identified acute embryotoxicity (i.e., lethality), as well behavioral and developmental effects, in the nominal micromolar range for all PFAS tested, which was correlated with fluoroalkyl chain length (and relative lipophilicity, i.e., log P), and suggested quantitatively comparable toxicity for next-generation (i.e, PFECA) and legacy (i.e., PFOA) variants. Metabolomic studies indicated targeting of liver, and specifically mitochondria, and associated metabolic pathways. Subsequently, toxicity assays were developed and applied to early life stages of mahi-mahi to assess toxicity of PFECA and PFOA. Mahi-mahi embryos were significantly more sensitive to PFAS with lethal concentrations extending into the environmentally relevant (e.g., parts-per-billion) concentration range. Finally, bioconcentration of PFECA and PFOA were comparatively assessed in embryos of zebrafish and flounder. These studies measured bioconcentration factors (BCF) ranging from 83 to 226-fold and 22 to 329-fold bioconcentration (relative to measured concentration in water) in embryos of zebrafish and flounder, respectively, with BCF values significantly correlated with fluoroalkyl chain length and log P values, in both cases. These findings raise concerns regarding PFECA as environmental toxicants, and specifically, as next generation replacements to legacy PFAS.
Previously Published In
Gebreab, K. Y., Eeza, M. N., Bai, T., Zuberi, Z., Matysik, J., O’Shea, K. E., ... & Berry, J. P. (2020). Comparative toxicometabolomics of perfluorooctanoic acid (PFOA) and next-generation perfluoroalkyl substances. Environmental Pollution, 265, 114928.
Gebreab, Kiflom, "Assessment of the Toxicity of Legacy and Next-Generation Perfluoroalkyl Substances (PFAS) in Early-Life Stages of Freshwater and Marine Fish" (2022). FIU Electronic Theses and Dissertations. 5029.
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