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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

In a ready biodegradability test, the test item was found 97% biodegradable and the 10-day window was met.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Three reliable studies on biodegradability in water are available. The first study (Sechaud P., 1990) has been selected as key study as it has been performed according to ISO guideline and the GLP principles. The second study (O'Reilly JV and Trehy ML, 1993) has been performed according to the SCAS method and has been selected as supporting study as the substance fulfilled the criteria for ultimate biodegradability. The third study (Litchfield CD, 1982) performed with a pre-adapted inoculum showed 36% of ultimate biodegradation and half lives of 2.5 and 3.2 days.

In the key study, the biodegradability of the dissolved test item, Dibasic esters (DBE) exposed in the test medium to aerobic micro-organisms as only source of carbon and energy was followed. The test was performed according to AFNOR T90-312 or ISO 7827 under GLP conditions. The test item concentration in the test vessel was corresponding to 40 mg C/L. The DOC was measured in intervals allowing following the curve of biodegradation up to 28 days. The curve reached a plateau at day 4. Thus the 10 -day window condition was met. The percentage of biodegradation of the test item DBE is 97% under the conditions of the study. Therefore, the test item is considered as readily biodegradable.

In the abiotic control, containing the test substance and mineral medium only, no elimination was noted after 28 days of exposure (based on DOC measurements). Thus, no abiotic elimination occurred under the test conditions.

The reference substance was more than 80% biodegraded within seven days of exposure, thus confirming the suitability of the activated sludge.In the toxicity control, containing the test substance, the reference substance and activated sludge (inoculum), the biodegradation was > 35% within 7 days. Thus, according to the test guidelines the test item was not inhibitory to activated sludge at the tested concentration.