Toxicokinetics, tissue distribution, and toxic potency of PFOS alternative OBS in adult zebrafish (Danio rerio) based on flow-through exposure system

Concerns regarding the possible health and environmental hazards of sodium p-perfluorous nonenoxybenzene sulfonate (OBS), a new substitute for perfluorooctane sulfonate, have been raised by its detection in a range of environmental matrices, animals, and people. Despite its widespread presence, research on the toxic effects and toxicokinetics of OBS remains limited. Therefore, in this study, we aimed to provide the first detailed investigation into how tissue distribution, bioaccumulation, and OBS exposure cause oxidative damage in adult zebrafish. Zebrafish were exposed to OBS at doses of 0, 10, and 100 μg/L for 28 days, following a 28-day depuration phase. Our findings indicate that OBS accumulated rapidly in zebrafish, with log kinetic bioconcentration factor (logBCF_k) values ranging from 2.48 to 2.70 and slow elimination rates (k_e = 0.0490-0.0643 d^-1). The blood, liver, and muscle were responsible for over 50 % of the total body burden of OBS, with tissue concentrations decreasing in the following order: blood > liver > intestine > gills > gonad > brain > muscle, suggesting a tissue-specific accumulation pattern. Molecular docking analysis showed that OBS exhibited binding energies of -2.71 and -3.82 kcal/mol with organic anion transporter 1 and human serum albumin, respectively. Additionally, chronic exposure to OBS resulted in significant liver damage in zebrafish, including ballooning, cytoplasmic vacuolisation, and oxidative stress. This study provides valuable experimental data on the toxicokinetics and in vivo toxicology of OBS in zebrafish, offering important insights for environmental risk assessments.