The Toxicity of Perfluoroalkyl Acids in Zebrafish (Danio rerio)

Cover: A whole-body autoradiogram of female zebrafish (Danio rerio) 10 day after exposure to 14 C-PFOA (above) and the corresponding section of the same fish (below) Abstract Perfluoroalkyl acids (PFAAs) are globally distributed synthetic chemicals. Their unique properties make them widely used, in industry and elsewhere. These are a group of compounds with varying carbon chain lengths and functional groups. The toxicity evaluation of PFAAs is important to better assess their organismal and environmental impact. The developmental toxicity of a group of PFAAs was evaluated in zebrafish (Danio rerio), using the embryotoxicity and locomotor behavior endpoints. Structure related relationships were examined using endpoints based on lethal and sublethal effect. The EC 50 based toxicity ranking of the PFAAs indicated that the toxicity pattern was governed by carbon chain length and attached functional group. The behavior analyses showed that the PFAAs have distinct patterns in terms of locomotor activity of larvae. Radiolabeled 14 C-PFOA was used to investigate the uptake, kinetics and distribution of the chemical in zebrafish. An uptake and elimination approach to experimentation was employed for kinetic assessment. A parallel equilibrium model bioconcentration strategy for 100-fold exposure range determined the internal body burden. Whole-body autoradiography and liquid scintillation techniques revealed the tissue distribution of PFOA. Remarkable levels of radioactivity were observed in target organs. The labeling of oocytes confirmed the maternal transfer of PFOA in zebrafish. In another study the effects of PFOA on reproduction and sexual development in zebrafish were evaluated. Reproductive traits like spawning, fecundity and fertilization were not altered in a short term experiment. The period of sexual differentiation in zebrafish was examined to determine the effects of PFOA on development, growth and gonad maturation. The development and growth of the zebrafish were not affected, but a trend in decreased survival in maternally exposed embryos was observed. The expression of Vtg mRNA level in the liver of PFOA-exposed male fish was not induced. Similarly, an inhibitory trend of PPARα mRNA expression in the liver of the highest PFOA exposed zebrafish was observed. The developmental toxicity ranking of PFAAs and kinetic assessment of PFOA with bioconcentration in zebrafish will provide an insight into risk assessment and replacement strategies of the compounds. And not equal are the good deed and the bad. Repel (evil) by that (deed) which is better; and thereupon the one whom between you and him is enmity (will become) as though he was a …