Application Of Four Test Methods Of Aquatic Ecotoxicology To Estimate The Toxicity Of Chemicals

Aquatic ecotoxicity tests play an important role in estimating the toxicity of chemicals. Almost every toxicant could finally get into the water body through various pathways.Several chemicals which are widely used were chosen in this study. They were methyl tert-butyl ether (MTBE), diphenylmethane diisocyanate (MDI) and bisphenol A. MTBE is widely used as additive for gasoline. MDI is widely used in producing polyurethane coating material. Bisphenol A is also an important industrial raw material. The toxicity of these chemicals was tested with three aquatic organisms at three different trophic levels:Scenedesmus obliqnus, Daphnia magna and Danio rerio. The major conclusions were summarized as follow:MTBE with low concentration (<577.08 mg/L) could stimulate the growth of Scenedesmus obliqnus, while MTBE with high concentration (>1000 mg/L) could inhibit its growth. The inhibition might result from the change of cellular structure and character in algae. The 72h-ECso of MTBE to inhibit the growth of Scenedesmus obliqnus was calculated to be 5190.28 mg/L.The auxiliary solvent, tween 80, did not show inhibition on the mobility of Daphnia magna (P>0.05). At 24h and 48h, the mobility of Daphnia magna did not show any difference in the MDI solution with the effective concentration of 74.76 mg/L, comparing with the control groups (P>0.05). The 24h-EC5o and 48h-EC5o of MDI on the inhibition of the mobility were both greater than 74.76 mg/L.Exposure to low doses of BPA (<2 mg/L) did not significantly affect the embryos’ survival or cause obvious malformation during the test. However, exposure to higher concentrations of BPA (^5 mg/L) reduced survival and caused changes in embryonic development, including delay of hatching, pericardial edema, axial malformations, cardiovascular system defect and development delay. The concentrations to cause 50% mortality (LC50) in embryos at 24 hours post fertilization (hpf) and 48 hpf were calculated to be 15.01 mg/L and 18.04 mg/L, respectively.Exposed to bisphenol A with the concentration of 11.18 mg/L for 24h, adult zebrafish had the mortality of 100%. Adult zebrafish exposed to 5.00 mg/L bisphenol A had the mortality of 35.71%at 96h. The 96h-LC50 was between 5.00 mg/L and 11.18 mg/L.