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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

OECD Guideline 301B, EU Method C.4-C, GLP, key study, validity 2:

First study: 29% biodegradation after 28 days (14-43%).

Second study: 42% biodegradation after 28 days (30-54%).

Non readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

One key study is available to assess the biodegradation of Chimexane HB. This study was performed using non adapted activated sludge from a predominantly municipal plant according to OECD 301 B and EU method C.4-C with GLP statement.

Two independent studies were carried out; on the first study the test item concentration was 40 mg/L in duplicates, corresponding to a carbon content (TOC) of 11.6 mg/L. the degradation kinetic and the course of degradation indicate a possible inhibitory effect of the test item on the activated sludge activity. Therefore the study was conducted using a lower concentration of test item (18 mg/L).

In the first study, the first test item replicate reached the 10% level after 15 days and came to a biodegradation rate of 43% after 28 days. The second test item replicate reached the 10% level after a long lasting adaptation phase of 28 days with a biodegradation rate of 14%. The mean biodegradation rate after 28 days was 29%. In the second study, the first test item replicate reached the 10% level after a long lasting adaptation phase of 25 days and came to a biodegradation rate of 30% after 28 days. The second test item replicate reached the 10% level after an adaptation phase of 12 days and came to a biodegradation rate of 54% after 28 days. The mean biodegradation rate after 28 days was 42%.

The high variability between replicates was observed at both concentrations, leading to the fact that the validity criterion related to the difference between replicates at the end of the test (or at the plateau) was not fulfilled.

The biodegradation of Chimexane HB was < 60% after 28 days in the CO2 evolution (modified Sturm) test. Under the test conditions, Chimexane HB must be regarded as not readily biodegradable.