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Administrative data

Link to relevant study record(s)

Description of key information

DT50 = 27.13 days (irradiated samples), 82.4 days (Phoenix, USA) and 127.7 days (Athens, Greece) [M-493228-01-1]

Key value for chemical safety assessment

Half-life in soil:
27.13 d

Additional information

One study (M-493228-01-1) was performed investigating the photolysis in soil OECD and OCSPP guidelines (OECD Draft Test Guideline, Phototransformation of Chemicals on Soil Surfaces, US EPA OCSPP Test Guideline No. 835.2410) and GLP. The photolytic route and rate of degradation of the test item was investigated in one soil under exposure to simulated sunlight and aerobic conditions in the laboratory for 11 days at 20 ± 2 °C (mean: 19.8 °C) and soil moisture of 55 ± 5% (mean: 53.4%) of the maximum water holding capacity. The study application rate was 21.8 µg per test system, equal to 7.3 mg test item/kg soil (dry weight). Duplicate test systems were processed and analyzed 0, 1, 2, 4, 7, 9 and 11 days after treatment. Overall mean material balances were 98.7% of applied radioactivity (%AR) for irradiated samples and 100.0%AR or dark samples. The maximum amount of carbon dioxide was 0.8 and < 0.1%AR at study end (DAT-11) in irradiated and dark samples, respectively. Formation of volatile organic compounds (VOC) was insignificant as demonstrated by values of < 0.1%AR at all sampling intervals for both irradiated and dark samples. Extractable residues ranged from 94.7 to 102.1%AR in irradiated samples and from 96.1 to 102.6%AR in dark samples. Non-extractable residues (NER) increased from < 0.1%AR at DAT-0 to 1.3 and 0.4%AR at DAT-11 in irradiated and dark samples, respectively. The amount of the test item decreased from 101.5%AR at DAT-0 to 77.4%AR at DAT-11 in irradiated samples and from 101.5%AR to 86.5%AR in dark samples, indicating degradation in irradiated samples. The degradation product was identified as a major degradation product in irradiated samples (7.0%AR at DAT-11) and in the dark samples (5.7%AR at DAT-11). The unidentified residues amounted to a maximum of 12.9%AR in the irradiated samples with no single component exceeding 1.9%AR and 7.5%AR in the dark samples with no single component exceeding 2.9%AR. The experimental half-lives for the test item were 27.13 and 44.31 days in the irradiated and dark samples, respectively. The corresponding net photodegradation rate constant (difference between irradiated and dark samples) was calculated to 0.0100 days-1, resulting in a net photodegradation DT50 of 69.3 days. Based on the experimental DT50 value of 27.1 days for irradiated samples, the DT50 of the test item under environmental conditions is calculated to be e.g. 82.4 solar summer days at Phoenix, Arizona, USA, and 127.7 solar summer days at Athens, Greece.