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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

Evidence suggests that ETU may degrade in water in some cases. Its metabolites are not persistent, not bioaccumulative and not classified as dangerous for the environment according to CLP criteria. In addition, ETU is not considered as PBT or vPvB either, being not B. Considering ETU as persistent is therefore a worst-case assumption for chemical safety assessment. Under this assumption, the water and soil RCR are all inferior to 1. Therefore, the chemical safety assessment performed under the worst-case hypothesis (persistency) does not indicate the need to further investigate ETU degradation in water. Based on its low log Kow value (log Kow < 3) and following the ITS of ECHA's Guidance information requirements and chemical safety assessment (Nov. 2012, v1.2, p. 139) the sediment compartment is not considered as a compartment of concern as ETU is not expected to bind to sediment.

Key value for chemical safety assessment

Additional information

Rapid and complete degradation of ETU can be observed in soils (Rhodes, 1977). In addition, partial mineralization is observed (Rhodes, 1977 ; Johannesen et al., 1996 ; Fomsgaard and Kristensen, 1999). In water, hydrolysis does not occur, but photolysis gives the same main metabolites as for soil biodegradation. The main metabolites of ETU in soil and/or water are glycine, ethyleneurea, hydantoin and sulphate. These substances (or their analogue) all have sufficient and adequate data for hazard identification. These substances are not considered as PBT or vPvB or classified in any hazard category according to CLP regulation EC 1272/2008. In addition, they are all readily biodegradable (except sulphate for which this property does not apply). It is therefore unlikely that they may cause any harm to the environment as metabolites of degradation of ETU present in the environment. Regarding PBT/vPvB classification, ETU is not expected to bioaccumulate (log Kow < 3). ETU is therefore not considered as PBT or vPvB. In the absence of any study on degradation of ETU in water, it is yet difficult to estimate the persistency of ETU in this compartment. However, it can be concluded that if ETU were degradable in water, the main metabolites poses negligible risks to the environment. Moreover, even if considering that ETU fulfils persistency criterion in water, ETU does not fulfil PBT or vPvB criteria, being not B. In addition, the environmental risk assessment does not indicate unacceptable risk for water or soil compartments when considering ETU as persistent in a worst case (RCR = 0.6 for freshwater ; RCR = 0.09 for marine water ; RCR < 0.01 for soil). Therefore, following annex IX, section 9.2.1.3, column 2 of the REACH regulation EC 1907/2006, no further testing is required on biodegradation of ETU in water as the chemical safety assessment does not indicate the need to. Therefore, conducting an OECD 309 study on biodegradation of ETU in surface water is not necessary.

The information of biodegradation in soils and water have been compiled in a position paper that is attached herein.