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Environmental fate & pathways

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Description of key information

The test substance was shown to be hydrolytically stable at pH 4, 7, and 9 [t1/2 (25°C) > 1 year].

Phototransformation on soil is likely to contribute to the degradation of the test item under outdoor conditions. Based on the experimental DT50 value of 3.9 days for irradiated samples, the half-life of the test item under environmental conditions is calculated to be e.g. 10.4 solar summer days at Phoenix (Arizona, USA) or 16.1 solar summer days at Athens (Greece).

Additional information

A GLP study according to the test method for the “Test on Hydrolyzability” of agricultural chemicals stipulated in the “Notification Concerning Test Data for Registration of Agricultural Chemicals” (12 Nohsan No. 8147) and the measurement method stipulated in the OECD Test Guideline 111 was conducted to determine the rate of hydrolysis in aqueous solution at pH values normally found in the environment (pH 4, 7 and 9) (M-398574-01-2, Tanaka 2004).

A preliminary hydrolysis test was performed at 50 °C in aqueous solution at pH 4, 7 and 9. The mean residual rate of the test substance was at least 90% at all pH levels under the test conditions used in the present study (50 °C, 5 days). Therefore, the test substance was shown to be hydrolytically stable (t1/2 (25 °C) > 1 year). On the basis of the results from the preliminary test, no further work was conducted.

One study (M-444181-01-1) was performed investigating the phototransformation on soil. Phototransformation of the 14C-labelled test item was studied in one soil under laboratory aerobic conditions for 9 days. The study followed the OECD Draft Test Guideline for phototransformation of chemcials on soil surfaces and the US EPA OCSPP Test Guideline No. 835.2410 for photodegradation on soil and was conducted in compliance with GLP. The test was performed in static systems consisting of 3 g soil dry weight. The test systems were either exposed to artificial irradiation or kept in the dark (control samples).

The experimental DT50 values of the test item in irradiated and dark control samples were 3.9 and 12.0 days, respectively, according to single first order kinetics. Based on the experimental DT50 value of 3.9 days for irradiated samples, the half-life of the test item under environmental conditions is calculated to be e.g. 10.4 solar summer days at Phoenix (Arizona, USA) or 16.1 solar summer days at Athens (Greece).

Mineralization was observed under the conditions of the test by formation of carbon dioxide up to 3.6% AR in irradiated samples and 0.4% AR in dark control samples.One transformation product ≥10% AR, transformation product A, was detected in irradiated samples with a maximum amount of 28.6% AR and one transformation product ≥ 10% AR, transformation product B, was identified in dark control samples with a maximum amount of 15.8% AR. Both metabolites were also observed in the respective other test system as minor metabolites: The transformation product B was identified with a maximum amount of 3.7% AR in irradiated samples and the transformation product A was identified with a maximum amount of 9.1% AR in dark control samples.

Formation of non-extractable radioactivity up to a maximum of 18.1% AR (DAT-9) in irradiated samples and of 6.8 % AR (DAT-8) and 6.6% AR (DAT-9) in dark control samples, respectively was observed.

The results of this study show that phototransformation in soil is likely to contribute to the degradation of the substance under outdoor conditions.