In
vivo dietary bioaccumulation experiments for 85 hydrophobic
organic substances were conducted to derive the in vivo gastrointestinal
biotransformation rates, somatic biotransformation rates, bioconcentration
factors (BCF), and biomagnification factors (BMF) for improving methods
for bioaccumulation assessment and to develop an in vivo biotransformation
rate database for QSAR development and in vitro to in vivo biotransformation
rate extrapolation. The capacity of chemicals to be biotransformed
in fish was found to be highly dependent on the route of exposure.
Somatic biotransformation was the dominant pathway for most chemicals
absorbed via the respiratory route. Intestinal biotransformation was
the dominant metabolic pathway for most chemicals absorbed via the
diet. For substances not biotransformed or transformed exclusively
in the body of the fish, the BCF and BMF appeared to be closely correlated.
For substances subject to intestinal biotransformation, the same correlation
did not apply. We conclude that intestinal biotransformation and bioavailability
in water can modulate the relationship between the BCF and BMF. This
study also supports a fairly simple rule of thumb that may be useful
in the interpretation of dietary bioaccumulation tests; i.e., chemicals
with a BMF<sub>L</sub> of <1 tend to exhibit BCFs based on either
the freely dissolved (BCF<sub>WW,fd</sub>) or the total concentration
(BCF<sub>WW,t</sub>) of the chemical in the water that is less than
5000