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Environmental fate & pathways

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Hydrolysis is no relevant degradation process of (2E)-1-[(6-chloropyridin-3-yl)methyl]-N-nitroimidazolidin-2-imine (DT50 = 240.5 day at pH 9 and 25 °C). At pH 4 and 7 at a temperature of 25 °C, the DT50 was estimated to be >1 year.

The main abiotic pathway for degradation of the target compound is photodegradation in air and the aqueous environment with a photolytical half-life of the substance being 0.85 hours and 0.76 days.

This is in agreement with the findings of a simulation study investigating the degradation of (2E)-1-[(6-chloropyridin-3-yl)methyl]-N-nitroimidazolidin-2-imine in natural pond water. The determined half-live was significantly reduced by the exposure to light and ranged from 10.7 in light exposed to 1271 days in nonexposed systems (recalculated to 12 °C).

In a simulation study the biodegradation of the substance was demonstrated under aerobic and dark conditions with different water/sediment systems. The substance was rapidly transferred from water to sediment, half-lives of the target compound at 22 °C ranged from 30 – 162 days (76 – 413 days, recalculated to 12 °C) in the water/sediment systems. After an incubation period of 92 days 14CO2 accounted for ≤2% of the initially applied radioactivity. Under anaerobic and dark conditions the degradation half-life of the test substance was found to be 69.1 and 60.4 days (recalculated to 12 °C).

Simulation tests on the biodegradation in different soil types, under aerobic conditions and continuous darkness, revealed a half-life of the test substance ranging from 399.1 days to >1 year with 16.7 to 25.1 % of the test substance bound as non-extractable residues after 100 days. After 100 days up to 10.0% of the applied radioactivity were mineralized.

The log Koc value of 2.14 indicates a low potential of the substance for adsorption to soil and sediment particles.

Furthermore, in field experiments no volatilization of the test substance within 24 hours was observed.

For the substance it is concluded that it will not accumulate in air and will not be transported through the vapour phase into other environmental compartments in relevant amounts.

Because of the low logKow (<= 3) the substance is expected to exhibit a low potential for bioaccumulation in fish.

No study on ready biodegradability is available for (2E)-1-[(6-chloropyridin-3-yl)methyl]-N-nitroimidazolidin-2-imine. However, since higher tier studies on the biodegradation of the test substance in water, sediment and soil are available no additional study on ready biodegradability is necessary. The PBT assessment and environmental classification can be derived based on the available higher tier studies. These studies indicate that the test substance is not readily biodegradable.