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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The substance is inherently biodegradable since significant mineralization (average 58%) was found within 28 days under conditions of an inherent biodegradation study.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

The key study for ready biodegradation (Häner 2014, OECD 301 B) shows that average 45.2% of the test material was mineralized within 28 days. Hence the substance is not readily biodegradable. However mineralization quantity is rather closer to the trigger value for ready biodegradation of 60% and furthermore, the plateau was not reached at the end of the test. This is also the case of the supporting ready biodegradation study which had been conducted following OECD 301 F protocol.

The key study for inherent biodegradability shows that the substance is inherently biodegradable: Average 91% of the test substance was eliminated from the aqueous phase within 28 days. The majority of eliminated substance, i.e. 58% had been mineralized within 28 days. OECD guideline for testing of chemical, Annex 1 Section 3, Part 1, April 2005 states "Since inherent biodegradability can be considered to be a specific property of a chemical, it is not necessary to define limits on test duration or biodegradation rates". Inherent biodegradation is confirmed by two supporting studies, i.e. an OECD 301 B and 301 F ready biodegradation test. Mineralization occurs in both tests above 20%. Mineralization results of OECD 301 B show that biodegradation averages 45,2% (mean of 47,9% and 42,5%) which is slightly below the trigger for ready biodegradation. OECD guideline for testing of chemicals, Annex 1 Section 3, Part 1, April 2005 states that "When results of ready biodegradability tests indicate that the pass level criterion is almost fulfilled (i.e. ThOD or DOC slightly below 60% or 70% respectively) such results can be used to indicate inherent biodegradability". In both tests the biodegradation plateau had not been reached yet, i.e. biodegradation was still ongoing at the end of the incubation period.