Tissue-Specific Uptake, Depuration Kinetics, and Suspected Metabolites of Three Emerging Per- and Polyfluoroalkyl Substances(PFASs) in Marine Medaka

Restrictions on legacy per- and polyfluoroalkyl substances (PFASs) have led to the widespread use of emergingPFASs. However, their toxicokinetics have rarely been reported.Here, tissue-specific uptake and depuration kinetics of perfluor-oethylcyclohexanesulfonate (PFECHS) and 6:2 and 8:2 chlorinatedpolyfluoroalkyl ether sulfonates (Cl-PFESAs) were studied inmarine medaka (Oryzias melastigma). Thefish were exposed tothese substances for 28 days (0.2 mu g/L), followed by a clearanceperiod of 14 days. The depuration constant (kd) of PFECHS [0.103 +/- 0.009 day-1(mean +/- standard deviation)] was reported for thefirst time. Among the six studied tissues, the highest concentrationsof 6:2 Cl-PFESA, 8:2 Cl-PFESA, and PFECHS were found in theliver [1540, 1230, and 188 ng (g of wet weight)-1, respectively] onday 28 while the longest residence times were found in the eyes (t1/2values of 21.7 +/- 4.3, 23.9 +/- 1.5, and 17.3 +/- 0.8 days, respectively). No significant positive correlation was found between thebioconcentration factors of the studied PFASs and the phospholipid or protein contents in different tissues of the studiedfish.Potential metabolites of Cl-PFESAs, i.e., their hydrogen-substituted analogues (H-PFESAs), were identified by time-of-flight massspectrometry. However, the biotransformation rates were low (<0.19%), indicating the poor capacity of marine medaka to metabolize Cl-PFESAs to H-PFESAs