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 and polycyclic aromatic hydrocarbons in the Danish environment. The Ph.D. project is expected to link exposure to POPs such as dioxin-like compounds and PAHs to effects in aquatic organisms and mammalian cell cultures by combining different in vivo and in vitro biomarkers in both laboratory and field studies. However, another perspective of this approach is exploring the potential of mammalian in vitro bioassays as screening tools for environmental samples and to contribute to a better integrated exposure assessment for aquatic organisms as well as for humans.