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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

A QSAR for the original substance 6PPD yielded a  bioconcentration factor of 568.7 was taken and justified as key value.
Measured BCFs of the two main hydrolysis products of 6PPD, 4-hydroxydiphenylamine and its oxidised form N-Phenylphenyl-p-benzoquinone monoimine, ranges from 3.3 - 49 and < 1.2 - 23, respectively. A further degradation product is 1,3-dimethylbutylamine. The BCF values range from 1.7 - 17. All three substances were investigated by the Chemicals Inspection & Testing Institute of Japan (CERI, 1995, National Institute of Technology and Evaluation 2002) according to OECD Guideline 305 C, using Cyprinus carpio as test organism.

Key value for chemical safety assessment

BCF (aquatic species):
568.7 dimensionless

Additional information

In a weight of evidence approach with a QSAR of 6PPD and a higher homolgue substance 8PPD (1,4-Benzenediamine, N-(1-methylheptyl)-N'-phenyl-). An experimental BCF study according to OECD 305 with 8PPD yielded a BCF of 1700. Supporting information is given by a valid QSAR for the higher homologue 8PPD which yielded a BCF of 2828 showing that QSARs for this group of substances tends to overestimate the result. Therefore, the QSAR for 6PPD resulting in a BCF of 568.7 is considered realistic and even conservative.

1,4-Benzenediamine, N-(1-methylheptyl)-N'-phenyl- ("8PPD") has a similar structure as 6PPD. It is a member of the paraphenylene diamine family. The difference is that 8PPD has an C8 branched aliphatic chain, whereas 6PPD has C6 branched aliphatic chain. Therefore 8PPD is more lipophilic than 6PPD what can be seen by the octanol water coefficients (8PPD: logKow 5.74; 6PPD: logKow 4.68). 8PPD is therefore considered a worst case for the BCF of 6PPD.

Since 6PPD hydrolyses rapidly within a half life of about 8 hours, information for the hydrolysis products 4 -hydroxydiphenylamine, N-phenyl-p-benzoquinone monoimine and 1,3 -dimethylbutylamine was taken into account.

A QSAR for 6PPD yielded a BCF of 568.7 indicating that the parent substance has a moderate tendency to accumulate but not meeting the criteria for B (BCF>2000) or vB (BCF >5000).