PHYSIOLOGICALLY-BASED TOXICOKINETIC MODELING OF 3 WATERBORNE CHLOROETHANES IN CHANNEL CATFISH, ICTALURUS-PUNCTATUS

A physiologically-based toxicokinetic model for fish was used to describe the uptake and disposition of three chlorinated ethanes in channel catfish (Ictalurus punctatus). Catfish were simultaneously exposed to 1,1,2,2-tetrachloroethane (TCE), pentachloroethane (PCE), and hexachloroethane (HCE) in fish respirometer-metabolism chambers to assess the kinetics of chemical accumulation in arterial blood and chemical extraction efficiency from inspired water. Chemical residues in tissues were measured at the end of each experiment. These data were used to evaluate the accuracy of model simulations and to form a basis for comparison with information collected previously from rainbow trout. TCE was at or near steady-state in catfish after 48 h. For PCE and HCE the time to steady-state appeared to be considerably longer than 48 h. Parameterized with in vitro chemical partitioning information, the model accurately simulated the accumulation of TCE in arterial blood and its uptake from inspired water, but consistently underestimated the uptake and accumulation of both PCE and HCE. The cause of these discrepancies was not conclusively determined; however, several possible sources of error were evaluated, including physiological and chemical partitioning inputs, and underlying modeling assumptions. A comparison of data sets and modeling efforts for rainbow trout and channel catfish suggests that gross similarities between the two species can be attributed to the comparability of relevant physiological and chemical partitioning parameters.