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Environmental fate & pathways

Biodegradation in water: screening tests

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Link to relevant study record(s)

Description of key information

In the key study Zenolide is 100% biodegraded within 28-day in a CO2 Evolution test (OECD TG 301B).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

Three studies are available for biodegradation screening of the test substance.

The key study is conducted according to OECD TG 301B (CO2 evolution test) and GLP. In this study, 10 mg/L of test substance (based on ThCO2) was exposed for 28 days under aerobic conditions to secondary activated sludge from a wastewater plant treating predominantly domestic wastewater. After the 28-day exposure period 100% of the test substance was biodegraded. The pass level of 60% was reached within 4 days after the start of the test, and thus the 10-day time window criterion was met. Based on these findings, the test substance is classified as readily biodegradable.

 

Secondly, a GLP-compliant OECD 301B study was available. The concentration of the test material was 18 mg/L. Although in this study the test substance was degraded significantly up to 78% in 28 -days, the 10-day window was not met (just below the criteria of 60% ThCO2) and therefore the substance was regarded as ready biodegradable but not meeting the 10-day window.

A third study was equivalent to an OECD 301C study (MITI (I) test). The study was not conducted under GLP. The concentration of the test material was 100 mg/L. The test substance was found ready biodegradable under the test conditions: 73% after 28 days, the 10-day window was met.