Toxicokinetics of DDE and 2-chlorobiphenyl in Chironomus tentans

Uptake, biotransformation, and elimination rates for DDE and 2-chlorobiphenyl (2-CB) were examined using fourth instar midge larvae (Chironomus tentans) under a water-only exposure. A two-compartment model that included biotransformation described the kinetics for 2-CB and a one-compartment model was used for DDE. The uptake clearance coefficient (k(u)) was 65.96 +/- 2.09 ml x g(-1) midge x h(-1) for 2-CB and 84.1 +/- 2.7 ml x g(-1) midge x h(-1) for DDE. DDE demonstrated no measurable elimination, while 2-CB showed elimination with faster elimination of parent compound (k(ep) = 0.100 +/- 0.008 h(-1)) compared to the polar metabolites (k(em) = 0.073 +/- 0.016 h(-1)). The biotransformation rate for 2-CB (k(m) = 0.031 +/- 0.005 h(-1)) appeared to be time-dependent with faster rates at the beginning of the accumulation process slowing to a constant once the midge was loaded with chemical. Experimental results indicate a difference in the ability of C. tentans to eliminate 2-CB and its metabolites more quickly than DDE, and these differences were related to the bioconcentration potential of the compounds.