A.C. Belfroid

Modelling the accumulation of hydrophobic organic chemicals in earthworms : Application of the equilibrium partitioning theory.

In this paper a method is developed which can be used to estimate the body burden of organic hydrophobic chemicals in earthworms. In contrast to the equilibrium partitioning theory, two routes of uptake are incorporated: uptake from interstitial water and dietary uptake. Although many uncertainties still remain, calculations show that for earthworms steady state body burdens are mainly determined by uptake from interstitial water. Under most circumstances, the contribution of dietary uptake is small, except for hydrophobic chemicals (log Kow > 5) in soils with a high organic matter (OM) content of ≈ 20 %. Under those conditions, estimates of the steady state body burden calculated with the equilibrium partitioning model, in which only uptake from interstitial water is taken into account, might result in a small underestimation of the real body burden of chemicals in earthworms.

The acute toxicity of chlorobenzenes for earthworms (Eisenia andrei) in different exposure systems.

Earthworms (Eisenia andrei) were exposed to different concentrations of two chlorobenzenes (1,2,3-trichloro- and pentachlorobenzene) using different routes of administration: in water, in soil, via food and on filter paper. Except for the contact paper toxicity test, lethal body burdens (LBBs) measured in these different exposure systems were similar for the same test chemical. LBBs for 1,2,3-trichlorobenzene varied between 0.44 and 2.1 μmol/g and for pentachlorobenzene between 1.29 and 2.34 μmol/g. These values correspond with literature data for fish. For 1,4-dichloro- and 1,2,3,4-tetrachlorobenzene LBBs measured with the contact paper toxicity test were 0.33 and 3.2 μmol/g, respectively. Exposure to hexachlorobenzene and hexabromobenzene using the contact toxicity test did not result in death within 48 hours.

Uptake of hydrophobic halogenated aromatic hydrocarbons from food by earthworms (Eisenia andrei)

The intestinal uptake of hydrophobic halogenated aromatic hydrocarbons by the earthworm Eisenia andrei was studied. In one experiment, worms were fed a single dose of manure contaminated with three chlorobenzenes, one polychlorobiphenyl (PCB 153) and octachloronaphthalene (OCN). Body burdens were followed during the subsequent 6 days. In the second experiment, worms were fed penta- and hexachlorobenzene, using multiple oral doses during 70 days. Steady state was reached in this experiment. Uptake efficiencies (E) derived by three different methods varied between 2.5 and 6.5% for 1,2,3,4-tetrachlorobenzene and OCN, and between 8.5 and 22% for the other compounds. Biomagnification factors (BMF) calculated for penta- and hexachlorobenzene using the body burdens at steady state were 0.03 and 0.07, respectively.

The induction and subsequent return to basal activity of liver enzyme activity in male C5/BL/6 mice after a single oral dose of 1,2,3,7,8-PnCDD or 1,2,3,6,7,8-HxCDD

Abstract The reduction of liver enzyme activity after an oral dose of 10 nmol/kg of 1,2,3,7,8-PnCDD (PnCDD) or 1,2,3,6,7,8-HxCDD (HxCDD) was followed in male mice of the C5/BL/6 strain. Two cytochrome P-450 related enzyme activities. EROD and PROD, were used as parameters for the induction of cytochrome P-450. For the PnCDD and HxCDD group, EROD activities were elevated 50 and 10 fold above control level on day 5. These elevations slowly declined, but were still significantly different from control level on day 54 for both groups. PROD activities were not elevated in both groups. Total cytochrome P-450 content of the PnCDD and HxCDD treated groups increased 3 and 2 fold and remained above control level until day 54 and 12 respectively.

Disposition, elimination and enzyme induction of 1,2,3,7,8-PnCDD, 1,2,3,6,7,8-HxCDD and 2,3,4,7,8-PnCDF in the liver of the mouse after a single oral dose☆

Abstract The disposition, elimination and cytochrome P450 related enzyme induction of 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PnCDD), 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin (HxCDD) and 2,3,4,7,8-pentachlorodibenzofuran (PnCDF) were studied in the liver of the male C57BL/6 mouse. Elimination of all compounds from the liver followed first-order kinetics. Half-lives for PnCDD, HxCDD and PnCDF were 15, 52 and 65 days respectively. 7-Ethoxyresorufin-O-deethylation (EROD) activity in the livers of the treated animals showed a good correlation with the liver tissue concentrations but the slopes of these liver concentration-response curves were not equal for all three compounds.