Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

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Additional information

If the substance is released to the environment it will be transported and distributed depending on its substance specific properties (e.g. physico-chemical properties, log Koc). Based on the vapour pressure of 2.7 x 10E-9 hPa at 20 °C it can be concluded that volatilization of the substance in the environment is not expected. Thus, the substance is expected to partition mainly to the water phase (water solubility: 69.1 g/L at pH 7) with slight potential for adsorption to organic material. Log Koc values in the range of 1.38 - 2.95 were derived (overall mean log Koc: 2.34). According to the classification system of Briggs, the adsorption Koc values would classify the substance as 'mobile', 'intermediate mobile' or 'low mobile' in soil, mostly depending on soil pH.

In the environment the substance will undergo several abiotic and biotic transformation/degradation processes. Hydrolysis was not considered to be a significant degradation pathway in the environment since Limited degradation was recorded at pH5, pH 7 and pH 9 after 30 d at 25 °C. Photolysis of the substance was studied in water and soil as well as in the atmospheric compartment. In the dark test systems of the water system, the parent compound did not degrade. There were no major or minor transformation products detected. In the irradiated test systems, the parent compound decreased from 100% of the applied amount at day 0 to 99.1% of the applied at the end of irradiation. No major transformation products were detected. The minor transformation products were formed at a maximum of 2.0% of the applied amount. All of the minor transformation products were transient in nature. The total unidentified radioactivity ranged from 0 to 4.1% of the applied amount. In soil the phototransformation DT50 in HCB silt loam was 90 experimental days, which is equivalent to 309 solar days in New River, AZ. The DT90 was 209 days (1,027 solar days). The DT50 in Pikeville loamy sand was 50.6 experimental days, equivalent to 173 solar days in New River, AZ. The DT90 was 168 days (576 solar days). No major degradation products were observed in either soil. Thus, in soil and water the test item was considered to be stable and photolysis is not considered to contribute significantly to the overall dissipation of the substance in the environment. A reaction with OH-radicals in the atmosphere leads to significant degradation of the substance in the atmosphere and a transport over large distances as well as accumulation is not expected. Bioaccumulation in biota and biomagnification within the food chain is not expected. The substance is characterized by a low log Pow of -1.362 at pH 7 and 23 °C indicating that the substance has a low potential for bioaccumulation.

The biodegradation of the substance was studied under aerobic and anaerobic conditions in water/sediment systems as well as in different soils. The substance was not readily degraded in the aerobic sediment/water test system. No major degradates were formed and minor degradates did not exceed 3% of the applied radioactivity. The major pathway of dissipation of the substance was adsorption to the sediment. In the case of the sandy loam sediment/water, non-extractable residues were 72.6 % by the end of the study, while in the silty clay loam sediment/water non-extractable residues represented 13.1 %of the applied radioactivity. Under aerobic conditions the substance was not readily degraded as well in sediment/water test system. No major degradates were formed. Minor degradates did not exceed 3.1% of the applied radioactivity. The major pathway of dissipation is the formation of bound (non-extractable) residues which reached 33.8% by the end of exposure. Different soils with varying physico/chemical properties were tested for aerobic degradation. Single first order DT50 ranged from 11 to 72 d. However, degradation kinetics is biphasic, most probably because the soil adsorption of the substance increases with time, so that the bioavailability of the substance decreases with time. In the anaerobic study with the parent substance, there was no significant change in the soil and water levels of the major soil metabolite so that no rate constant can be calculated. In conclusion the substance is not considered to be rapidly degraded in the environment.