Comparison of toxicokinetics and toxic effects of PFOS and its novel alternative OBS in zebrafish larvae.

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS), a novel alternative to perfluorooctanesulfonate (PFOS), is widely used in industry as a surfactant, firefighting foam and photographic material. The occurrence of OBS in the aquatic environment has been recently reported, but little information is available on its accumulation and toxic effects in aquatic organisms. In this study, zebrafish larvae (3 d post-fertilization) were subjected to OBS (10, 100 μg/L) and PFOS (10 μg/L) for a period of 48 h, followed by a 24 h of depuration period. The bioconcentration and depuration kinetics, oxidative stress and possible molecular mechanisms of OBS and PFOS were investigated in zebrafish larvae. Our results showed that the uptake and depuration of both OBS and PFOS fitted well with a first-order kinetic model. The uptake rate constant of OBS was similar to that of PFOS, but the depuration rate constant was much higher than PFOS with a half-life of 69.7-85 h for OBS and 222.2 h for PFOS. The calculated BCFs of OBS and PFOS were 238.0-242.5 and 644.2, respectively. In our acute toxicity assay, the enhanced expression of Nrf2 protein accompanied by the upregulation of CAT and SOD protein expressions indicated OBS and PFOS induced oxidative stress in zebrafish larvae, and the Nrf2-ARE signaling pathway was involved in this process. Collectively, OBS has a lower bioconcentration potential than PFOS, but its toxic effect on oxidative stress was comparable to PFOS in zebrafish larvae.