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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Ready biodegradation experiment according to EU Method C.4-D / OECD 301F: 81 % degradation after 28 days - readily biodegradable.  
Supporting information:
Calculation with BIOWIN v4.10 (EPIWIN software by US-EPA), Prediction results are not consistent. Predictions range from rapid degradation to slow degradation. Overall Ready Biodegradability Prediction: No.
"Ultimate" aerobic biodegradation test according to ISO 7827: 68 % degradation - not persistent.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Screening data concerning biodegradation in water are available as experimental study results as well as QSAR predictions. The biodegradability of the test substance was investigated in accordance to EU Method C.4-D, which corresponds in principle OECD Guideline 301 F (Kanne, 1993). The test substance (100 mg/L) was weighed into the prepared mineral medium and inoculated with activated sludge, resulting in an inoculum concentration of 30 mg TS/L. Incubation was done for 28 days at 20 +/- 1 °C under aerobic conditions. Biodegradation during this time was determined based on the measured oxygen demand, which was recorded with the help of a respirometer. The Theoretical Oxygen Demand (ThOD) is reported as 2627 mgO2/g. After 28 days, the test substance attained 81 % degradation. In accordance to internationally accepted criteria of the OECD, the test substance is "readily biodegradable". Aniline was used as reference substance, incubated under identical conditions and attained 75 % degradation at the end of the test.

Furthermore, the potential for biodegradation in water of the test substance was predicted with the computer program BIOWIN v4.10 (EPIWIN software) of US-EPA (Chemservice S.A., 2011). The program calculates with seven different models: Linear Model (Biowin 1), Non-linear Model (Biowin 2), Ultimate Biodegradation Timeframe (Biowin 3), Primary Biodegradation Timeframe (Biowin 4), MITI Linear Model (Biowin 5), MITI Non-linear Model (Biowin 6) and Anaerobic Model (Biowin 7). The overall result describes the ready biodegradability prediction of the compound.

According to the Linear Model as well as the Non-Linear Model, the substance is biodegrading fast. The Ultimate Biodegradation Timeframe is "weeks", and the Primary Biodegradation Timeframe reveals "days-weeks" for 4-phenylbutenone. Both MITI Models predict that the substance is not readily biodegradable, which is also the prediction as overall result. Also under anaerobic conditions the substance is suspected to be not biodegraded fast.

The Ultimate and Primary Timeframe indicate that 4-phenylbutenone is not persistent in the environment. This is supported by an available publication which reports about the investigation of environmental impact of wastewater form a chemical-pharmaceutical plant (Brorson et al., 1994). In this context, the test substance was investigated according to the "ultimate" aerobic biodegradability test ISO 7827. After an exposure time of 28 days, 4-phenylputenone attained 68 % degradation, however, it is also reported that the study leaves some uncertainty about this result since a carrier of bentonite was applied.

As conclusion, 4-phenylbutenone is considered as "readily biodegradable" and therefore also as "not persistent" in the environment.