Tissue uptake, distribution and elimination of (14)C-PFOA in zebrafish (Danio rerio)

Perfluorooctanoic acid (PFOA) is a long-chain perfluorinated chemical that has been shown to be non-degradable and persistent in the environment. Laboratory studies on bioconcentration and compound-specific tissue distribution in fish can be valuable for prediction of the persistence and environmental effects of the chemicals. In the present study male and female zebrafish (Danio rerio) were continuously exposed to 10μg/L of radiolabeled perfluorooctanoic acid ((14)C-PFOA) for 40 days, after which the exposed fish were transferred to fresh clean water for another 80 days wash-out period. At defined periodic intervals during the uptake and wash-out, fish were sampled for liquid scintillation counting and whole body autoradiography to profile the bioconcentration and tissue distribution of PFOA. The steady-state concentration of (14)C-PFOA in the zebrafish was reached within 20-30 days of exposure. The concentration-time course of (14)C-PFOA displayed a bi-exponential decline during washout, with a terminal half-life of approximately 13-14 days. At steady-state the bioconcentration of (14)C-PFOA into whole-body fish was approximately 20-30 times greater than that of the exposure concentration, with no differences between females and males. The bioconcentration factors for liver and intestine were approximately 100-fold of the exposure medium, while in brain, ovary and gall bladder the accumulation factors were in the range 15-20. Whole-body autoradiograms confirmed the highest labeling of PFOA in bile and intestines, which implies enterohepatic circulation of PFOA. The (14)C-PFOA was also observed in maturing vitellogenic oocytes, suggesting chemical accumulation via yolk proteins into oocytes with plausible risk for adverse effects on early embryonic development and offspring health. The bioconcentration at several (14)C-PFOA exposure concentrations were also investigated (0.3-30μg/L). This showed that bioconcentration increased linearly with tank exposure in the present in vivo model under steady-state conditions. From this model tissue concentrations of PFOA can be predicted when the external exposure level is known. The present study has generated experimental data on PFOA kinetics in zebrafish that can be valuable for aquatic environmental risk assessment.