Joint acute toxicities of five herbicides to zebrafish

<bold>Objective</bold> In order to explore the combined toxicity of mixed herbicides on zebrafish.this study investigates acute joint toxicities of metamifop，penoxsulam，propanil，pyrazosulfuron and cyhalofop-butyl to zebrafish. <bold>Method</bold> On the basis of single toxicity test，the combined acute toxicities of binary and multivariate herbicides were tested according to 96 h-LC₅₀ values（toxicity rate=1∶1）. <bold>Result</bold> The results showed that the 96 h-LC₅₀ values of metamifop，Penoxsulam，propanil，Pyrazosulfuron and cyhalofop-butyl for zebrafish were 1.048，10.00，4.440，10.00 and 3.819 mg/L，respectively.The combined effects of binary herbicides（cyhalofop-butyl + penoxsulam，cyhalofop-butyl + metamifop，cyhalofop-butyl + propanil，metamifop + penoxsulam）and the ternary herbicides（penoxsulam + pyrazosulfuron + cyhalofop-butyl，metamifop + propanil + cyhalofop-butyl）on zebrafish showed an antagonistic effect.The combined effects of binary herbicides（cyhalofop-butyl + pyrazosulfuron，pyrazosulfuron + penoxsulam，metamifop + propanil）on zebrafish showed an additive effect at 24 h and synergistic effects were observed at 48，72，and 96 h. <bold>Conclusion</bold> The research and production or the application of compound herbicides should prioritize the combination of herbicides with antagonistic effect toxicity.These results can provide data support for ecological risk assessment of herbicides combined exposure in aquatic environment.