Interrelationships between bioaccumulation of organic trace pollutants (PCBs, organochlorine pesticides and PAHs), and MFO-induction in fish.

1. Hydrophobic compounds that are more easily biotransformed (e.g. PAHs) generally show less bioaccumulation in fish than the more persistent PCBs and DDTs. 2. In lake Nieuwe Meer, with the highest levels of organic micropollutants, the hepatic MFO activity was elevated in three fish species. This indicates that MFO activity might be a sensitive indicator for organic micropollutants in the aquatic environment. 3. Activities of the 3-MC type inducible isozymes were most pronounced in all three fish species studied. Though further research is required, indications for the existence of a PB-type inducible enzyme system have been demonstrated for two fish species, i.e. pike and eel. 4. Fish liver enlargement as a consequence of MFO induction could not be demonstrated in fish from the most polluted lake. 5. In fish, a correlation was observed between PCB or OCP tissue concentrations on the one hand, and hepatic MFO activities on the other. The low PAH fish/sediment ratios are further reduced when MFO systems are induced due to organic micropollution. The interrelationship between bioaccumulation and enzyme induction demonstrates the importance of an integrated study of these phenomena in field research.