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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

A test on ready biodegradability was conducted according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)). After 28 days 77PD showed 12 % degradation. Therefore 77PD is not ready biodegradable (Bayer, 1990a).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Some primary and secondary hydrolysis products (p-benzoquinone,p-hydroquinone and the relevant amines) are readily biodagradble.The question arises why the PPDs are not readily biodegradable, although some of their hydrolysis products (p-benzoquinone, p-hydroquinone, aniline and 1,4 -dimethylpentylamine) are known to biodegrade quite rapidly. Thus, limited biodegradation could have been expected. A possible explanation for this contradiction is the fact that p-hydroquinone is highly toxic against bacteria: Based on an EC50 of 71 mg/L and a NOEC of 1 mg/L the resulting PNEC(STP) is 0.71 mg/L. Biodegradation tests according to the OECD 30x series are typically performed with initial concentrations of 100 mg/L.