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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Quinoline can be considered as readily biodegradable based on the soil study (5.2.3).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Neither valid ready biodegradation nor inherent biodegradation test is available with quinoline. However, information is available from different tests performed either in anaerobic conditions, either from primary biodegradation tests.

An ultimate anaerobic test showed 97 % of degradation within 4 weeks with a lag time of 15 days.

Most of the available studies aim to evaluate the primary biodegradation of quinoline, and usually with adapted bacteria or enriched cultures. In these conditions, the biodegradation is very fast (100% in few days). When non adapted cultures are used, the biodegradation seems to be also fast (85% in 6.25 days at the highest tested quinoline concentration of 150 mg/L).

In anaerobic conditions, the primary degradation by unadapted freshwater sediments amounts to 100% in 45 days in sulfate-reducing conditions, and in 23 days in methanogenic conditions. The rate is much slower in denitrifying conditions (23% after 83 days). With adapted cultures, in anaerobic conditions, a total mineralisation is observed in within 48 h.

The primary degradation product identified in different studies in aerobic and anaerobic conditions is 2 -hydroxyquinoline. Another possible degraation product is 2,3 -dihydroxyquinoline observed in aerobic conditions.

In the part 5.2.3, a study in soil is presented showing a very quick and total mineralisation of quinoline. According to the Guidance on information requirements and chemical safety assessment, chapter R7b page 192 (version 1.1, May 2008), the ready biodegradation can be deduced from a study on soil because the biodegradation rate is usually slower in soil than in aquatic media, specially for sorptive substances. This assumption is strengthened by the study performed by Smith (1992) with marine sediments, showing that addition of clays reduce the quinoline degradation rate due to adsorption.