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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

According to REACH Annex VII, a screening test on biodegradation in water does not need to be conducted, as the substance is inorganic. 
The test item is composed of zinc chloride, a zinc hexacyanocobaltate complex as well as tertiary butyl alcohol plus polypropylene glycol, whereas the parent substance completely dissociates in contact with water. The biodegradability of zinc chloride and zinc hexacyanocobaltate complex cannot be determined as they are purely inorganic and thus cannot serve as energy source for microorganisms. Solely physico-chemical processes (sorption to the sewage sludge) might cause their elimination during sewage treatment rather than biological processes.
The inorganic fraction (zinc chloride and the zinc hexacyanocobaltate complex) accounts for approximately 68 % (w/w) of the substance. Concluding, the majority of the substance cannot be degraded in a sewage treatment plant resulting in the most stringent classification as not readily biodegradable, even if the organic fraction was assumed to be completely degradable. A test on ready biodegradability would thus not result in new information.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information