Uptake, elimination and biotransformation of N-ethyl perfluorooctane sulfonamide (N-EtFOSA) by the earthworms (Eisenia fetida) after in vivo and in vitro exposure

N-ethyl perfluorooctane sulfonamide (N-EtFOSA) is commonly known as the active ingredient of sulfluramid. It can be degraded to perfluorooctane sulfonic acid (PFOS) in biota and environment. Earthworms (Eisenia fetida) were exposed with N-EtFOSA to examine the bioaccumulation, elimination and metabolism of N-EtFOSA by the earthworms after in vivo and in vitro exposure. N-EtFOSA could be biodegraded in quartz sands to perfluorooctane sulfonamide (FOSA) and PFOS. In the in vivo tests, in addition to parent N-EtFOSA, three metabolites, including perfluorooctane sulfonamide acetate (FOSAA), FOSA and PFOS also accumulated in earthworms as a result of N-EtFOSA biotransformation, with FOSA as the predominant metabolite. The bioaccumulation factor (BAF) and uptake rate coefficient (k(u)) of NEtFOSA from sand were 20.4 and 2.41.d(-1), respectively. The elimination rate constants (k(e)) decreased in the order FOSAA (0.130.d(-1)) > N-EtFOSA (0.118.d(-1)) > FOSA (0.073.d(-1)) > PFOS (0.051.d(-1)). The biotransformation of N-EtFOSA in earthworm was further confirmed by the in vitro test involving incubation of earthworm homogenates with N-EtFOSA. This work provides evidence on the accumulation and transformation of N-EtFOSA in terrestrial invertebrates and will be helpful to explore the indirect sources of FOSA and PFOS in environmental biota. (C) 2018 Elsevier Ltd. All rights reserved.