Soil and plant diet exposure routes and toxicokinetics of lindane in a terrestrial isopod

In most studies dealing with effects of toxic substances in saprotrophic is opods, animals are exposed to the test substance through contaminated food. Because these animals can be in a close contact with the soil surface, the substrate, as an exposure pathway, should not be neglected. Here the autho rs analyze the toxicokinetic behavior of lindane (gamma-hexachlorocyclohexa ne [gamma-HCH]) in the isopod species Porcellionides pruinosus, comparing t wo exposure routes: food and two soil types (artificial Organisation for Ec onomic Cooperation and Development [OECD] soil and a natural agricultural s oil). In the feeding experiment, a strong decrease of gamma-HCH concentrati on over time was observed on the food material, with the animals showing a broader range in chemical assimilation efficiency values (averaging 17.7% a nd ranging from 10 to 40%). The gamma-HCH bioaccumulation results indicate that when animals incubated under both soil types reached a steady state, t hey displayed much higher body burdens (1,359.60 pg/animal on OECD soil and 1,085.30 pg/animal on natural soil) than those exposed to contaminated foo d (43.75 pg/animal). Kinetic models also revealed much lower assimilation a nd elimination rates in the food experiment (20.66 pg/d and 0.10 pg/d) than in both soil experiments (238.60 pg/d and 350.54 pg/d for the assimilation rate and 0.19 pg/d and 0.32 pg/d for the elimination rate). Differences in results between exposure routes are discussed according to equilibrium-par titioning theory and the enhanced relevance of the substrate exposure route is analyzed under future prospects on chemical toxicity testing using isop ods.