Combined toxicity effects of MTBE and pesticides measured with Vibrio fischeri and Daphnia magna bioassays - Article Review

Review:

Combined toxicity effects of MTBE and pesticides measured with Vibrio fischeri and Daphnia magna bioassays

M.D. Hernando, M. Ejerhoon, A.R. Fernandez-Alba, Y. Chisti

            This article review is about the use of Vibrio fischeri and Daphnia magna bioassays as a tool to measure the combined toxicity effects of methyl-tert-butyl ether (MTBE) and several components of pesticides Diuron, Linuron, Dichlofluanid, Sea nine, Irgarol and tributyltin (TBT). MTBE is widely used as fuel oxygenate in gasoline commonly contaminates aquatic ecosystem and has a low acute and chronic toxicity when tested alone. However, combination of chemicals found in aquatic environment affects the toxicity of the individual compounds. It can be synergistic, additive or antagonistic effects. The study’s goal are to know the combined effects of pesticides found in lake, marinas and river which were Diuron, Dichlofluanid, Sea nine 211, Irgarol 1051, Linuron and Tributyltin (TBT) and MTBE. V. fisheri and D. magna bioassay was used to evaluate the toxicity level of MTBE and pesticide alone and together the combined effects. They quantified the toxic effect using EC_50. They also evaluated the time generated by the toxic response of V. fisheri and D. magna.

            Chemical were purchased and tested individually and as a combination. The compounds were then evaluated using V. fisheri bioassay and the light was evaluated using Biotoxt^TM.. D. magna bioassay used Daphtoxkit^TM and was assessed by noting the motility of D. magna. The data were also converted into a Mixture Toxicity Index. The EC₅₀ was replicated six times for reproducibility. Chemical analyses were also used to detect the disappearance of MTBE because it is highly volatile, highly water soluble and a persistent pollutant.

MTBE is toxic to invertebrates at concentrations of 57 to >1000 mg/L and the value of MTBE’s toxicity on D. magna is EC₅₀=720 mg/L and is consistent with the reported 96-h EC₅₀ measurement of 681 mg/L. As a result the typical concentration of MTBE in environment does not harm aquatic life. Presence of MTBE enhances the EC₅₀ of Diuron, Dichlofluanid, TBT and Linuron and while Sea nine and Irgarol were not raised.

For us, this study is actually reliable for future studies as the result were able to answer their objectives in terms of identifying the effect of the MTBE to the bioassays and the time needed to take effect (in the results). The results obtained were all consistent to the goal when the effects on the bioassays were clearly identified. Even if the paper has no recommendations, we say, the results are reliable and can be used as a reference for parallel studies.