DNA adduct levels in fish from pristine areas are not detectable or low when analysed using the nuclease P1 version of the 32P-postlabelling technique.

In order to understand and apply DNA adduct formation in fish liver as a biomarker for aquatic pollution, information concerning the natural background levels in noncontaminated organisms, caused by endogenous compounds, is of fundamental importance. In this study, DNA adducts were analysed in liver of 11 fish species from arctic and sub-arctic areas in the northern Atlantic using the nuclease P1 version of the 32P-postlabelling technique. The collected fish were assumed not to have been influenced by anthropogenic pollution apart from possible long-range transported pollutants. As polycyclic aromatic hydrocarbons (PAHs) are thought to be fundamental in forming the type of DNA adducts detected by the method used, biliary PAH metabolite levels were measured in a selection of the investigated species. In all investigated individuals, the levels of PAH metabolites were undetectable. Controlled on-site exposure experiments with benzo[a]pyrene (polar cod) and laboratory experiments with crude oil (polar cod and Atlantic cod) were conducted. DNA adducts were formed in both these species. The field-sampled fish showed undetectable levels of DNA adducts or levels just above the detection limit. The present study supports the assumption that when DNA adducts are detected by the nuclease P1 version of the 32P-postlabelling method in fish liver, it can be interpreted as DNA damage caused by pollutants.