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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

In accordance with column 2 of REACH Annex IX, the water and sediment simulation test does not need to be conducted as the substance is readily biodegradable.

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Additional information

Testing for the endpoint ‘biodegradation in water and sediment’ is waived as the test substance is readily biodegradable. However, several studies are available for read-across substances and are provided for completeness purposes. The CO2 evolution study by West (1996) was undertaken in a river microcosm resulting in 100% degradation in two days with the read-across substance 2,2',2''-nitrilotriethanol (CAS 102-71-6). The half-lives in water-sediment and water were 0.2 to 0.6 days and 0.8 to 1.7 days, respectively.

 

An OECD 308 Guideline study was undertaken by Itrich (2010) in accordance with GLP compliance using the read-across substance C10-13 sodium 4-decylbenzenesulfonate (CAS 68411-30-3). The biodegradation in sediment was evaluated in an aerobic die-away study using sediment from Lytle Creek, Wilmington, Ohio and run for 148 days. The test substance was aerobically biodegraded in sediment after 148 days, as follows:

­  60.8% was mineralised,

­  14.4% was associated with solids,

­  24.5% remained as parent, and

­  1.4% was metabolites.

 Primary degradation was best described by a two compartment first order model (r2 > 0.99). The process was biphasic with two pools of material exhibiting different degradation rates. Pool A was presumably the more readily bioavailable test material in the aqueous phase. Pool B was presumably the less bioavailable test material bound to solids (sorbed). The rate constants for primary degradation were:

­  1.5 per day (pool A)

­  0.007 per day (pool B)

 Mineralisation (14CO2 production) was best described by a First Order Model (r2 > 0.99), indicating that parent and metabolites were equally bioavailable to undergo mineralization. The rate constant for mineralization was 0.06 per day.

 

In a related OECD 308 Guideline study by Itrich (2010) using the same read-across substance C10-13 sodium 4-decylbenzenesulfonate (CAS 68411-30-3). The biodegradation in sediment was evaluated in an aerobic die-away study using sediment from Ohio River, Cincinnati, Ohio and run for 92 days. The test substance was aerobically biodegraded in sediment after 92 days, as follows:

­  42.1% was mineralised,

­  28.5% was associated with solids,

­  29.8% remained as parent, and

­  0% was metabolites.

Primary degradation was best described by a two compartment first order model (r2 > 0.99). The process was biphasic with two pools of material exhibiting different degradation rates. Pool A was presumably the more readily bioavailable test material in the aqueous phase. Pool B was presumably the less bioavailable test material bound to solids (sorbed). The rate constants for primary degradation were:

­  0.5 per day (pool A)

­  0.009 per day (pool B)

 Mineralization (radio-labelled CO2 production) was best described by a First Order Model (r2 > 0.99), indicating that parent and metabolites were equally bioavailable to undergo mineralisation. The rate constant for mineralisation was 0.06 per day.