Risk assessment of the herbicide Clomazone to aquatic life.

Due to their widespread distribution and toxic nature, pesticides may have a serious impact on the aquatic environment. Clomazone (2-(2-chlorophenyl)methyl-4,4-dimethyl-3-isoxazolidinone) is a post emergence herbicide widely used in paddy rice fields in South Brazil, with activity against Gramineae like Echinochloa crusgalli. The recommended application rate (RAR) of the emulsible concentrate is 1.4L/ha. The high vapor pressure of Clomazone (1.44x10-4mm Hg 25oC) contributes to volatilization losses. Thus, the contamination of the aquatic environment by the herbicide may occur in aerial application. Other ways of the aquatic ecosystem contamination may occur by drainage from irrigated rice fields. In this work, studies were conducted with two primary producers and with a primary consumer in order to evaluate the risk of Clomazone to aquatic life based on maximun application rates (MAR).