Comparative toxicity of imidacloprid, of its commercial liquid formulation and of diazinon to a non-target arthropod, the microcrustacean Daphnia magna

This study examined Daphnia magna chronic responses to imidacloprid, the formulated product Confidor SL 200 (imidacloprid), and diazinon. D. magna reproduction was evaluated for 21 days in solutions with imidacloprid concentrations ranging from 0-40 mg/L. The LOEC after 21 days ranged from 2.5-10 mg/L of imidacloprid for different reproduction parameters. The formulated product showed effects at lower concentrations than the active ingredient, with a LOLC of 40 mg/L. This may suggest synergism between imidacloprid and solvents in formulated product. Testing for the chronic effects of imidacloprid showed decreasing enzyme activity in D. magna, but it was not attributed to be an early indicator of stress. The authors also calculated risk quotients for imidacloprid and diazinon based on aquatic detections, but noted that there were only four published detections of imidacloprid. The risk quotients suggested that diazinon levels in the environment are more harmful to aquatic invertebrates than imidacloprid, but there was not adequate imidacloprid data. The authors noted that with increasing use of imidacloprid, they would expect to see significantly higher concentrations in future monitoring. They also noted that the literature shows variable and species-specific imidacloprid toxicity that is difficult to extrapolate between species.

Authors: 
Jemec, A., T. Tisler, D. Drobne, K. Sepcic, D. Fournier, and P. Trebse
Journal: 
Chemosphere
Year published: 
2007