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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The test substance can be considered to be "not readily biodegradable". 

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Regarding biodegradation in water (screening tests) an experimental (key study, reliability 2) as well as two QSAR results (supporting study, reliability 2) are available for the substance 2,4,6 -triisopropyl-m-phenylene diisocyanate. The study was conducted according to EU Method C.4 -D (Manometric Respirometry Test) under aerobic conditions under exclusion of light at 20 +/- 1 °C (Müller, 1997). In this test activated sludge (adaption not further specified) out of domestic sources is incubated for 28 days with 100 % test substance. The observation parameter is the O2 consumption. Aniline (purity >= 99.5 %, initial test concentration: 100 mg/L) was used as reference substance whereby 77 % after 14 days and after 28 days 81 % of the reference was degraded. In contrast the test substance showed no degradation (0 %) after 4, 14 and 28 days. In the used concentration the substance was not bacteriotoxic. Although the test was performed according to well-established scientifically test method the reliability can just assigned with Klimisch 2 (reliable with restrictions) due to the fact that no GLP statement is available.

The first prediction for biodegradability was performed with the computer program BIOWIN v4.10 (EPIWIN software) by US-EPA (Chemservice S.A., 2011). The program calculates with seven different models: Linear Model (Biowin 1), Non-linear Model (Biowin 2), Ultimate Biodegradation Timeframe (Biowin 3), Primary Biodegradation Timeframe (Biowin 4), MITI Linear Model (Biowin 5), MITI Non-linear Model (Biowin 6) and Anaerobic Model (Biowin 7). The overall result gives the ready biodegradability prediction of the desired compound. According to Biowin 1 and 2 the substance is biodegrading fast. The Ultimate Biodegradation Timeframe is given in weeks till months, and the Primary Biodegradation Timeframe gives weeks as result. Both MITI Models predict that the substance is not readily biodegradable, which is also the overall prediction result. Also under anaerobic conditions the substance is not expected to be degraded fast. No GLP criteria are applicable for the usage of this tool and the QSAR estimation is easily repeatable. Due to the available data the test substance has to be regarded to be "not readily biodegradable".

Further prediction was performed with the help of the Start plug-in in Toxtree (v.2.1.0) by Chemservice S.A. (2011). The START (Structural Alerts for Reactivity in Toxtree) plug-in is a developed rule base, which estimates the biodegradability potential of a chemical compound based on structural alerts compiled from the Canadian EPA (START2008). The chemical was assigned to the class III - unknown.