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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

TAME is characterised as “inherently biodegradable, not fulfilling criteria” for non-adapted sewage sludge.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, not fulfilling specific criteria

Additional information

Two closed bottle tests (OECD 301D) are available (Hazleton Europe, 1995; Slovnaft VÚRUP, a.s., 2005a). The percentage of biodegradation observed is ca. 5% after 7 days in both studies. Thus, TAME is not readily biodegradable in the aquatic environment according to the standardised aerobic ready-biodegradation tests. As no test results from standard inherent test systems for aquatic biodegradation are available, conclusions are made according to the non-standard tests (e. g. Jensen and Arvin, 1990).

However, certain adapted micro-organisms are capable of degrading MTBE (e. g. Kharoune et al., 2002). Thus, a well adapted industrial STP plant is able to degrade the substance. High degradation rates have been observed in non-standard tests using special types of inoculum, pure cultures and mixed cultures (e. g. Cowan and Park; Hernandez-Perez et al., 2001; Kharoune et al., 2002). These studies show that at least some microbial species are capable to degrade TAME and to use it even as their sole carbon source.

It may be concluded that TAME is inherently biodegradable under certain conditions in the aquatic aerobic environment. However, the non-standard test data available indicate that TAME degradation might not fulfil the test criteria (OECD 302). Therefore, in the further assessment the substance is assumed to be “inherently biodegradable, not fulfilling criteria” for professional and consumer releases and on the regional scale.