BIOACCUMULATION OF LIPOPHILIC SUBSTANCES IN FISH EARLY-LIFE STAGES

Accumulation of C-14-labeled polycyclic aromatic hydrocarbons, naphtha lene, phenanthrene, pyrene, and benzo(a)pyrene and polychlorinated bip henyl (PCB) congeners PCB 31 and PCB 105 with a log octanol/water part ition coefficient (K-ow) range from 3.37 to 6.5 was investigated in eg gs and larvae of zebra fish (Brachydanio rerio), and in larvae of cod (Gadus morhua), herring (Clupea harengus), and turbot (Scophthalmus ma ximus). Significant differences in the uptake and elimination rate con stants between eggs and larvae of zebra fish were seen. The low rate o f uptake and the tower elimination rate of eggs did, however, lead to bioconcentration Factors (BCFs) comparable to those for larvae. As bio transformation of xenobiotics in embryonic and larval stages was indic ated to be insignificant compared to juvenile/adult stages, body burde ns of readily biotransformed chemicals may be higher in fish early lif e stages. Because weight and lipid content did not differ much between the investigated species, the main reason for the variability in BCFs between marine species (cold water species) and freshwater species (w arm water species) was considered to be caused by differences in expos ure temperatures that affect the degree of biotransformation. Due to t he smaller size of larvae and thus an increased total surface of the m embranes per unit fish weight, steady-state conditions were reached at a faster rate in early life stages than in juvenile/adult life stages . The lipid-normalized bioconcentration factors (BCFL) were linearly r elated to K-ow, but BCFL was, in general, higher than K-ow, indicating that octanol is not a suitable surrogate for fish lipids. Differences in bioconcentration kinetics between larvae and juvenile/adult life s tages are considered to be the main reason for the higher sensitivity, with respect to external effect concentrations, generally obtained fo r early life stages of fish.