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Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Link to relevant study record(s)

Description of key information

Not readily biodegradable, but rapid primary degradation observed.

Key value for chemical safety assessment

Additional information

Two relevant guideline studies on the biodegradability of the substance are available. The first study followed OECD guideline 301 B and was conducted with activated sludge taken from a municipal sewage treatment plant as inoculum. Two test substance concentrations i.e. 10 mg/L and 20 mg/L respectively were established. Based on CO2evolution a degradation rate of 24% was determined at 10 mg/L, whereas at a substance concentration of 20 mg/L a degradation rate of 12% was detected (Ciba-Geigy Ltd. 1984).

The second study – a supporting study (Nihon Ciba-Geigy K.K.Biodegradation in water) – measured O2-consumption after 14 d as relevant endpoint and revealed a biodegradation rate of -5.5%. Direct measurements of the single components by HPLC revealed that the diester remained at 98.2 to 99.9% whereas the monoester remained at 42.4. to 43.7% indicating the possibility of biodegradation of the monoester. As major metabolite of the monoester 3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] propionic acid was confirmed. In conclusion, this study showed that the diester form was not biodegraded at all and almost all amount remained unchanged. However, the monoester form was hydrolyzed to 3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] propionic acid at about 57.0%. PEG-300 was degraded at about 40% and 88%, respectively.


Following these studies, the substance cannot be regarded as readily biodegradable, however at least the monoester form undergoes rapid primary degradation and thus cannot be regarded as persistent.