Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

7ppd was shown to have 0% biodegradation occur in a biodegradation test over 35 days following ASTM No. 3 and was determined to be hyrolytically unstable.

Additional information

Conclusion on degradation:

According to available information on degradation, all PPDs in question are not readily biodegradable and no significant biodegradation is observed but full abiotic degradation takes place.

The pathway of hydrolysis occurs in the same manner for all PPDs: Half-lives for the primary degradation are in the range of 3.4 to 8 hours. Primary degradation products are 4 -hydroxydiphenylamine and oxidised form of it (N-phenyl-p-benzoquinone-monoimine and N-Oxide (4-(phenylnitroso)benzen-1-olate or 4-(phenylnitroso)cyclohexa-2,5-dien-1-one)) and 1,4 -dimethylpentylamine.

There are some indications that secondary degradation is faster in case of 77PD. Common secondary hydrolysis products of all PPDs are p-Benzoquinone and p-Hydroquinone and an amine. In the case of 7PPD the amine is Aniline. The question arises why the PPDs are not readily biodegradable, 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. Biodegradation tests according to the OECD 30x series are typically performed with initial concentrations of 100 mg/L. This concentration is fare above the water solubility of 7PPD (0.7 mg/L) and it can be expected that bacteria are not able to digest insoluble particles. In the atmosphere rapid photodegradation takes place by reaction with photochemically produced OH radicals. The half-life of 7PPD is calculated to be 1.7 hours in that test system.