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Based on read-across with the chemical closely related substance C.I. Pigment Blue 15 (CAS No 147-14-8; EC No 205-685-1), C.I. Direct Blue 264 is considered as "not readily biodegradable".

To identify the degradation products of C.I. Direct Blue 264, a simulation in water biodegradation test according to OECD 309 was performed in natural surface water for 61 d under aerobic conditions in dark at 20 ± 2 ºC. The results show that degradation of the test substance was observed during incubation in surface water. Reliable quantification of the degradation is in most cases not possible as parent and metabolites are partially not separated by HPLC and eluting within the same retention time range. Seven metabolites could be identified by structure and semi-quantitative analysis by LC-HR-MS indicates degradation rates >50% for the observed components of the test substance (C.I. Direct Blue 264).

As additional study, the probability of biodegradation of the major degradation product N-[3-(dimethylamino)propyl]-1,3-dioxo-2,3-dihydro-1H-isoindole-5-sulfonamide was predicted to be not readily biodegradable using the BIOWIN model in EPI-Suite.

Regarding soil and sediment, the biodegradation of the test substance has been waived due to the low adsorption potential of the substance (log Koc = 0.96) according to REACH regulation, annex IX, column 1. Therefore, a sediment and soil simulation study is not required.


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