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Environmental fate & pathways

Biodegradation in water: screening tests

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The potential for ready biodegradability of sodium 2,4-dichlorophenoxyacetate (CAS No. 2702-72-9) was investigated in one study. This test was conducted according to OECD Guideline No. 301D, Closed Bottle Test (1992), under GLP conditions. The test material, at a concentration of 2 mg/L was incubated in activated sludge for 28 days, reaching a biodegradation value of 2.27% at test termination. As these results indicate that sodium 2,4-dichlorophenoxyacetate could be toxic to the inoculated bacteria, an additional experiment was conducted, at a lower concentration (1 mg/L), using a toxicity control. This second experiment reported 67.17% biodegradation of the test material on day 28. The results found in the toxicity control (8.37%) indicate that this substance might be inhibitory at higher concentrations. Based on this information, the substance can be considered as not readily biodegradable.

Sodium 2,4-dichlorophenoxyacetate (CAS No. 2702-72-9) is soluble in water, where it will be rapidly dissociated, mainly into 2,4-dichlorophenoxyacetic acid (CAS No. 94-75-7). The inherent biodegradability of this substance was investigated by Sorys (2004). This study was performed according to OECD Guideline 302B, Zahn-Wellens/EMPA test, under GLP conditions. Degradation of the test material reached 99% on day 28, showing that 2,4-dichlorophenoxyacetic acid is inherently biodegradable.