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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Not readily biodegradable (according to OECD criteria).

Key value for chemical safety assessment

Additional information

Since no data on the registered substance are available a read-across to a similar pigment (CAS 81-77-6) is used to cover this endpoint. The ready biodegradability of the analogue substance was tested in a guideline study according to OECD 301B. The biodegradation rate was determined by measuring the CO2 evolution of domestic activated sludge at test substance concentrations of 11 mg/L and 20.6 mg/L, respectively. After the 28 day incubation period a degradation rate of < 10 % was observed [Ciba-Geigy Ltd., 1989].

This result supports one model calculation which was conducted with CATALOGIC v5.11.5. The calculation with CATALOGIC v5.11.5 (BOD 28 days MITI (OECD 301C) v06.07) resulted in ca. 0.04 % biodegradation after 28 d. Even though the structural domain was correct with only 52.94 % (47.06 % unknown) the results support the overall conclusion that the pigment is "not readily biodegradable".

Moreover, the pigment is practically insoluble and therefore considered to be essentially not bioavailable. Due to the large molecular size, cellular uptake of the pigment is unlikely. Hence intracellular biodegradation, which is the main degradation route of bacteria, is probably low. It can be concluded that the substance is likely to persist in the environment. For this reason no ready degradation studies are proposed.