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

A physiologically-based toxicokinetic model for fish was used to descr ibe 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 hexachl oroethane (HCE) in fish respirometer-metabolism chambers to assess the kinetics of chemical accumulation in arterial blood and chemical extr action efficiency from inspired water. Chemical residues in tissues we re measured at the end of each experiment. These data were used to eva luate the accuracy of model simulations and to form a basis for compar ison with information collected previously from rainbow trout. TCE was at or near steady-state in catfish after 48 h. For PCE and HCE the ti me to steady-state appeared to be considerably longer than 48 h. Param eterized with in vitro chemical partitioning information, the model ac curately simulated the accumulation of TCE in arterial blood and its u ptake 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 partitioni ng inputs, and underlying modeling assumptions. A comparison of data s ets and modeling efforts for rainbow trout and channel catfish suggest s that gross similarities between the two species can be attributed to the comparability of relevant physiological and chemical partitioning parameters.