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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

[S,S]-EDDS acid and its trisodium salt have been shown to be readily biodegradable - with biodegradation rates of at least 75% within 28 days - in the modified Sturm test (Guekens, 1993a; Schowanek et al. 1997), unacclimated river water die-away test (Jaworska et al. 1999; Schowanek et al. 1997), semi-continuous activated sludge test (Schowanek et al. 1997) and the batch-activated sludge tests with acclimated and unacclimated sludge (Schowanek et al. 1997). Where relevant, these tests were conducted in line with corresponding OECD Guidelines.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

A ready biodegradability test using activated sludge and carried out according to OECD Guideline 301 B (in compliance with GLP) indicated that, in an aerobic aqueous medium, trisodium EDDS was readily biodegradable. In this modified Strum test, initial test concentrations were 10 and 20 mg/L, and biodegradation reached at least 83% and 88% by days 28 and 35, respectively (Geukens, 1993a; Schowanek et al. 1997).

In an unacclimated river water die-away test, degradation of [S,S]-EDDS [it is not clear whether the test was performed on the radio-labelled acid or its corresponding trisodium salt] was similar to that seen in the modified Sturm test, reaching 75%, corresponding to a half-life of about 6.3 days. This suggests that biodegradation also occurs under realistic environmental conditions (Jaworska et al. 1999; Schowanek et al. 1997).

In addition, in a (semi-)continuous activated sludge (SCAS) test carried out according to OECD Guideline 302A, trisodium EDDS was readily biodegradable. Over a 7 -day acclimation period 40 mg/L was added to the test system, and biodegradation reached 97% by day 7 of the test period (Schowanek et al. 1997).

Batch-activated sludge tests on [S,S]-EDDS [it is not clear whether the test was performed on the radio-labelled acid or its corresponding trisodium salt] with acclimated and unacclimated sludge indicated biodegradation of 94% and 84%, respectively, within 28 days (Schowanek et al. 1997).

[Data on trisodium EDDS is considered relevant to use for understanding the potential biodegradability of EDDS acid, and is acceptable for using as read-across information].