Some environmental persistent organic pollutants (POPs) can be highly toxic and pose risk for both natural fauna populations and humans. POPs can disrupt an array of molecular and cellular mechanisms causing endocrine disruptions, cancer and teratogenic effects. Potentially, POPs can interfere with embryo development and reproduction. At present, there is only limited knowledge of the potential effects of dioxin-like compounds (DLCs) and polycyclic aromatic hydrocarbons (PAHs) in fish from the Danish marine environment. In this project we tried to link exposure to POPs such as DLCs and PAHs to effects in marine fish by combining different in vivo and in vitro biomarkers in both laboratory and field studies. A combination of chemical measurements and biological effect measurements was applied within the frame of integrated environmental assessment approach covering effects on different levels of biological organization using the coastal fish eelpout (Zoarces viviparus) as a test organism. As a part of this investigation, natural seasonal variations in the vitamin status based on retinoids (vitamin A), vitamin E and carotenoids in the fish have been studied to assess the potential for changes in vitamin status being employed as in vivo biological effect measurement. The potential of mammalian in vitro bioassays as a screening tool for environmental samples has been explored.

An overall conclusion is that as most biomarker approaches have their limitations, one has to apply integrated approach using both chemical and biological methods on different levels of organization in order to assess the environmental impact of POPs in real field conditions. PAH metabolites in bile and enzymatic induction of CYP1A in liver can be applied as biomarkers of the exposure to POPs in eelpout, as both biomarker responses have shown capable to facilitate the estimation of POPs impact in different geographical areas and also in the laboratory exposure experiment. Vitamin status and teratogenic effects like abnormal fry development and embryo malformations in eelpout can be indicative of biological effects of POPs, although causal relationships between exposure and effects are more difficult to establish. Vitamin status based on retinoids, carotenoids and vitamin E in adult female eelpouts and its fry has shown to vary significantly, according to seasonality and in relation to reproductive cycle of the fish. The hypothesis of retinoid depletion caused by POP’s in fish can lead to abnormalities in embryo development has been corroborated. CYP1A enzymatic induction was introduced into this causal chain as an intermediate link via a statistically strong biomarker response to chemical exposure and positive, but statistically not significant relation between CYP1A induction and the level of several polar retinoids, which in itself is indicative of retinoid mobilization and consequent depletion. Together, the selected approaches confirm that POPs can induce adverse biological effects on eelpout, and that this fish species is a reliable bioindicator for environmental studies of biological effects of contaminants in fish from coastal waters.