Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

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Biodegradation in water, screening test: tertiary butyl acetate was partially degraded by non-adapted sewage sludge over a period of 28 days in an OECD 301D Closed Bottle test: at the end of the 28 exposure period, 50% degradation was seen. Supporting BOD/COD ratio data similarly indicated inherent, but not ready, biodegradability. It is concluded that tertiary butyl acetate is inherently biodegradable, not fulfulling specific ECHA criteria.

The test substance t-Butyl acetate was shown not to significantly mineralise in surface water in a pelagic water simulation test (conducted at 12°C), with calculated half-life (DT50) values of 138 days (at 20 µg/L) and 252 days (at 100 µg/L).

The experimental conduct of this study was challenging mainly due to the high volatility of the test substance. Although the Henry’s Law constant (83.2 Pa.m3/mol) was within the parameters considered acceptable for slightly volatile substances in the OECD 309 guideline (<100 Pa.m3/mol), under experimental conditions it was considered that the test substance was too volatile for this guideline test. Despite the nature of the test substance, the test design achieved acceptable mass balances and considerable efforts were undertaken to identify potential degradates. Therefore, it was considered that the study results and methodology met the requirements of the relevant study guideline.

Under the specific conditions of this test, mineralisation from surface (pelagic) water is not expected to be a significant method for removal of t-butyl acetate from the environment.

In isolation t-Butyl acetate could be concluded to be persistent in surface waters under the conditions of this test, however this ignores its main route of removal from fresh waters which will be from volatilisation to the atmospheric compartment and subsequent rapid photodegradation (estimated half-life for atmospheric degradation is 19.7 days).

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