Concentration Fluctuation of Fipronil in Seedling Granules in Rice Paddies and Nearby River System

Abstract

Concentrations of an insecticide fipronil in paddy water and paddy soil were investigated as well as water and sediment form the Kaname River. The partition coefficient (Kd) of fipronil obtained from the elution test using the sampled paddy soil was compared to the rate of fipronil concentration in paddy soil to that of paddy water. When the paddy field was dammed, the rate decreased due to elution of fipronil from the paddy soil, and when water was circulated through the paddy, the fipronil concentration in paddy water decreased and the rate increased. Risk assessment for aquatic environment which was based on environmental concentration and registration standards of fipronil regarding prevention of damage to flora and fauna indicated that adverse effects were anticipated by fipronil up to one month after rice planting. Risk assessment for human health which was based on environmental concentration and registration standards of fipronil regarding water pollution indicated the need for alternative pesticides that are less toxic than fipronil.