Biotransformation, oxidative stress and genotoxicity biomarkers in mosquito fish exposed to PW.

Produced water (PW) is a complex mixture containing residual hydrocarbons, trace elements, naturally occurring radioactive material and potentially toxic treatment chemicals such as biocides, dispersants, detergents and scale inhibitors used in hydrocarbon production. The aim of this study was to compare the activity of CYP1A with PAH bile metabolites, phase II, oxidative stress and genotoxicity biomarkers to evaluate the PW toxicity in mosquito fish. This research is part of the ENI S.p.a. project entitled “Advanced Processes for Oily Water Treatment”. The test organism, mosquito fish (Gambusia affinis), was divided into male and female groups and exposed for 8 and 30 days to PWs from an Italian on-shore oil plant and from an Italian off-shore gas platform. Specimens were also exposed to water and sediment from an Italian ship canal (Navicelli Channel). The induction of phase I (EROD, BPMO activity) and phase II (GST activity) biotransformation systems, FACs, LPO, enzymatic antioxidants (GPX, GR, CAT), a non-enzymatic antioxidant (glutathione—GSH) were investigated. DNA damage was evaluated in erythrocytes by single cell gel electrophoresis (Comet assay). The experimental groups showed significantly higher EROD and BPMO activity compared with the control group during the exposure to PWs from gas and oil installations. A decrease of CYP activities was observed, in comparison with control, during the exposure to water and sediment from ship canal, probably due to high concentration of lipophilic contaminants. The CYP1A responses were also compared with the other biomarkers, in particular positive Spearman correlations between EROD (or BPMO) activity and PAH metabolites in bile and Comet assay were observed.