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Environmental fate & pathways

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Isotianil is regarded as degradable by photolytically induced processes in air with an estimated half-life for the reaction with OH-radicals of 4.47 days (24 h day; OH-concentration 0.5E+06 OH/cm³).

Studying the phototransformation in water resulted in half-lives of 1.8 to 2.3 days in natural water under experimental conditions. Corresponding to 7.4 to 9.4 real days in Tokyo spring. Isotianilwas rapidly and extensively degraded during aqueous photolysis at 25 ± 2 °C. The photolysis produced a complex mixture of components from both the natural water and distilled water solutions. The major degradate was anthranilonitrile amounting for up to 14.5% of the applied radioactivity via amide cleavage. A number of minor degradates were also formed and they were gradually mineralized to 14CO2. Based on the results of this study, photolysis will be a major route of elimination for Isotianil from the aquatic environment.

Photodegradation in soil resulted in a DT50 value of 17.6 days for irradiated samples and 10.7 days for the dark controls. Based on the experimental DT50 value of 17.6 days for irradiated samples, the DT50 of Isotianil under kind of extreme environmental conditions is calculated to be 50.5 solar summer-days at Phoenix, Arizona, USA. There was no difference in the degradation pathway of dark and irradiated soil samples, despite the fact that Isotianil in dark samples degraded much faster and formed higher amounts of the degradation products, i.e. of DCIT-acid. From this study, it is evident that phototransformation of Isotianil on soil surface does not contribute to the elimination of this compound from the environment. No metabolites of Isotianil formed exclusively by sunlight irradiation on soil surface have to be considered for risk assessments.

Based on a study performed according to OECD 111, the hydrolysis of Isotianil is considered as slow to moderate under environmental conditions (25 °C) with specific half-lives of 60.8 – 71.4 days (pH 7) and 53.7 – 55.0 days (pH 9).