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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Anthraquinone was tested for the ready biological degradability in Closed Bottle Test. In this 28-day study the degradation of 62.0 % of Anthraquinone was attained in the end of study but condition of 10-day window was not fulfilled (degradation of 51.9% was achieved 10 days after the start of degradation). Anthraquinone is considered ready biodegradable but failing the 10-day window.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window

Additional information

In closed bottle test, comparable to the OECD TG 301D with inoculum containing mixed population of microorganisms obtained from secondary effluent of wastewater treatment plant the biodegradation of Anthraquinone (purity of main component 9,10 -Anthraquinone was 98.9%) was investigated.

The start of degradation, which point is taken as the time when 10% of the substance has been degraded, was by 7thday of the test. Degradation of 51.9% was achieved ten days after the start of degradation.

In this 28-days study the degradation of 62.0% of Anthraquinone was attained in the end of study (Nachtigallová A., M.Sc., 2009).

According to Regulation No 1272/2008 Anthraquinone is considered not ready biodegradable, because according to Article 4.1.2.9.5. of this Regulation the substance is considered rapidly degradable in the environment if in 28-day ready biodegradation studies, at least the following level of degradation is achieved for test based on oxygen depletion or carbon dioxide generation: 60 % of theoretical maximum. These levels of biodegradation must be achieved within 10 days of the start of degradation which point is taken as the time when 10 % of the substance has been degraded.

A negative result in a test for ready biodegradability does not mean that the chemical will not be degraded under relevant environmental conditions and persist in the environment. A failed ready biodegradability test indicates that further testing under less stringent test conditions should be considered at the next level.

In terms of risk assessment Anthraquinone is considered to be readily biodegradable but failing 10-d window.