Lipid Content and Time-to-Death-Dependent Lethal Body Burdens of Naphthalene and 1,2,4-Trichlorobenzene in Fathead Minnow (Pimephales promelas)

For naphthalene (NAPH) and 1,2,4-trichlorobenzene (TCBz), lethal body burdens (LBB) of 8 ± 3.1 mmol/kg wet wt (ww) and 14 ± 4.5 mmol/kg (ww), respectively, were determined in fathead minnow (Pimephales promelas). LBBs of both compounds were found to increase with increasing lipid content and time-to-death of fish within the same aquarium. The correlation with time-to-death suggests that besides lipid content at least one other factor causes intraspecies variation in LBBs. When intraspecies variation is excluded by comparing mean LBBs from different aquaria and exposure regimes, LBBs still vary with time-to-death. In contrast to the situation within one aquarium, between different aquaria and exposure regimes often a decrease in LBB with time-to-death is found. The present study and others indicate that LBBs can vary with time-to-death. Therefore, a time-independent LBB cannot be assumed.