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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

A study designated as the Key Study for 7PPD indicates that the substance is not readily biodegradable with 0 % biodegradation after 35 days.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Additional tests are available for 6PPD. Due to the analogous structure to 6PPD (the difference is an additional methyl group in 7PPD) the study from the supporting substance was used to read across. Both substances have similar physico-chemical properties. They hydrolyse rapidly and have a common hydrolysis product. The test conducted according to the OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)) showed a 2% degradation for 6PPD after 4 weeks, and the following degradation products were detected: Phenylbenzoquinone imine and 1,3-dimethylbutylamine. Further degradation products were stated: p-benzoquinone, 4-hydroxydiphenylamine, aniline.

As 7PPD is known to hydrolyze rapidly (half-life 7 h), the occurrence of the respective amine of 7PPD (1,4-dimethylpentylamine) would be expected also in biodegradation tests. As such amines are readily biodegradable, this would normally be reflected in a higher biodegradation rate. According to stoichiometric relations a biodegradation of about 40% could theoretically be achieved. The data from different sources however clearly show, this is not the case. A possible explanation of this fact that ready biodegradation tests are performed typically in concentrations of 100 mg/L which is far above the solubility of 7PPD in water (0.7 mg/L).