Toxicokinetics of DDE and 2-Chlorobiphenyl in Chironomus tentans

Abstract.

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 · g⁻¹ midge · h⁻¹ for 2-CB and 84.1 ± 2.7 ml · g⁻¹ midge · 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.