Bioaccumulation, Biotransformation and Oxidative Stress of 6:2 Fluorotelomer Sulfonamidoalkyl Betaine (6:2 FTAB) in Earthworms (<i>Eisenia fetida</i>)

As a novel perfluorooctane sulfonate (PFOS) alternative, 6:2 fluorotelomer sulfonamide alkylbetaine (6: 2 FTAB) has been detected in the environment and biotas. However, its behaviors and toxicity in earthworms remain unclear. Here, earthworms (<i>Eisenia fetida</i>) were exposed to 6:2 FTAB to investigate its bioaccumulation, biotransformation and toxicity. Results indicated that 6:2 FTAB could be biodegraded in soil into perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), perfluorobutanoic acid (PFBA) and perfluoropropionic acid (PFPrA). The uptake rate constant (<i>k</i>_u) and the bioaccumulation factor (BAF) of 6:2 FTAB in earthworms were 0.0504 g_oc g_ww⁻¹ d and 1.65 g_oc g_ww⁻¹, respectively. 6:2 FTAB was biotransformed to form PFHxA, PFPeA, PFBA and PFPrA in earthworms after in vivo and in vitro exposure. The aerobic bacteria isolated from worm gut could degrade 6:2 FTAB to form PFPeA and PFHxA, while the anaerobic bacteria did not contribute to 6:2 FTAB biodegradation in worms. Peroxidase (POD) and superoxide dismutase (SOD) activities were significantly increased, while no significant changes were observed for catalase (CAT) activities, demonstrating activation of the primary antioxidant defense system against oxidative stress in earthworms after exposure to 6:2 FTAB. The significant increase of glutathione-S-transferase (GST) activities suggested indirect evidence on the conjugation of 6:2 FTAB or its metabolites in phase II of detoxication. This study provides important information on the fate of 6:2 FTAB in earthworms.