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Environmental fate & pathways

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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 -Anthraquinonewas 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.

 

For PBT assessment according to Guidance on information requirements and chemical safety assessment Chapter R.11: PBT Assessment, 2008: “if the substance is readily biodegradable, or if the criteria for ready biodegradability are fulfilled with exception of the 10-day window, there is no reason to perform further biodegradation tests for the PBT/vPvB assessment. The conclusion is that the substance is not fulfilling the criteria for Persistence (P)”.