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7PPD has a relatively high Koc value of 11480 (calculated). As the hydrolyis occurs fast (half-life 5.15h) also the hydrolysis product(s) are taken into account. For 4 -Hydroxydiphenylamine, the Koc was calculated to be 398.

The distribution of the parent compound and the two hydrolysis products 4 -hydroxydiphenylamin and N-Phenyl-p-benzoquinone monoimine was calculated using the Mackay distribution model:

 Compartment  7PPD


N-phenyl-p-benzoquinone monoimine

 Air (%)  0.17  0.16 0.09 
 Water (%)  4.06  95.87  99.2
 Soil (%)  47.43  2.19  0.39
 Sediment (%)  47.95  1.77  0.32
 Suspended sediment (%)  0.3  0.014  0.003
 Biota (%)  0.03  0.001  0.0002
 Aerosol (%)  0.06  0.001  0.0001

The model indicates that the parent compound has a high affinity to soil and sediment whereas the primary hydrolysis products are expected to be distributed mainly in water.

It should be mentioned here that the distribution modelling gives only a rough indication about the distribution of a substance in the environment. Paraphenylenediamins are transported to the environment mainly by tyre abrasion. Tyre road wear particles are distributed differently than estimated by the distribution model: About 78% end up in soil and about 22% in water and sediment (Danish EPA 2015). Thus, soil is the most relevant compartment.