TOXICITY OF HEXACHLOROBENZENE TO HYALELLA-AZTECA AND CHIRONOMUS-TENTANS IN SPIKED SEDIMENT BIOASSAYS

Fourteen-day, whole-sediment toxicity tests using the amphipod Hyalell a azteca and the midge Chironomus tentans were conducted on spiked sed iment samples representing a range of hexachlorobenzene (HCB) concentr ations. High rates of survival and growth relative to controls were ob served in both test species. No observed effects concentrations (NOECs ) were equal to the highest HCB concentration tested (42 mg/kg, normal ized to 1% total organic carbon). Available literature on the aquatic toxicity of this hydrophobic chemical shows an absence of lethal and s ublethal effects from exposure to HCB at or below water solubility con centrations, and toxicity from exposure to dissolved HCB in sediment p orewater therefore would not be expected. Because whole-sediment toxic ity tests integrate exposure to HCB dissolved in porewater and adsorbe d to particles, it was considered possible that exposure via sediment ingestion could cause toxicity; however, no such effect was observed i n this study.