BIOCONCENTRATION OF POLYCHLORINATED DIBENZO-P-DIOXINS AND POLYCHLORINATED DIBENZOFURANS IN GUPPIES AFTER AQUEOUS EXPOSURE TO A COMPLEX PCDDPCDF MIXTURE - RELATIONSHIP WITH MOLECULAR-STRUCTURE

Guppies (Poecilia reticulata) were exposed to a complex mixture of pol ychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofura ns (PCDFs) in water for 21 days. It is the first study in which accumu lation data of 15 toxic dioxins and furans were quantified simultaneou sly in a continuous exposure experiment. First-order uptake rate const ants (k1) and first-order elimination rate constants (k2) were calcula ted for the toxic, laterally substituted congeners. Bioconcentration f actors (BCFs) were calculated from both the ratios of concentrations i n fish and water and from the ratios of the rate constants. Dioxins an d furans were selectively accumulated in fish tissue. The non-laterall y substituted congeners were either not observed in fish tissue or sho wed lower BCF values than their laterally 2,3,7,8-substituted isomers. The log BCF values of laterally substituted congeners ranged from 3.9 0 +/- 0.06 to 5.27 +/- 0.07. BCF values were smaller than predicted by existing linear relationships with log K(ow). Several phenomena were discussed with respect to the observed bioconcentration behaviour, suc h as limited bioavailability, reduced lipid solubility, reduced membra ne permeability and biotransformation. Furthermore, the similarity bet ween structure-activity relationships considering bioaccumulation in f ishes and the Ah-affinity in mammals was discussed.