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Biodegradation in water: screening tests

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Description of key information

Biodegradation
Biodegradation in water: screening test (Weight of Evidence approach)
2-Propenoic acid, C16-18-alkyl esters (read across)
In the Ready Biodegradability (CO2-Evolution) Test the degree of biodegradation of the test substance at the end of exposure was determined to be 50-60 % CO2/ThCO2.
 
Dodecyl acrylate (C12) (read across)
The degree of biodegradation of the test substance was 80-90 %CO2/ThCO2 after an exposure period of 28 days.The read across substance (mixture of CAS no. 2156-97-0 and 21643-42-5) is readily biodegradable under the conditions of this test.
 
Icosyl acrylate (C20) (read across)
The degree of biodegradation of the test substance was 60-70 %CO2/ThCO2 after an exposure period of 60 days.The test item was biodegradable under the enhanced test conditions of this test.
 
Conclusion
Considering the results of the biodegradation studies with Dodecyl acrylate/ Laurylacrylate (C12), 2-Propenoic acid, C16-18-alkyl esters and Icosyl acrylate/ Behenylacrylate (C20) a Weight of Evidence approach was made. Taking all data together, 2-Propenoic acid, docosyl ester is considered to be biodegradable under enhanced test conditions.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window

Additional information

A Weight of Evidence approach was done with other long-chain acrylates to assess the biodegradation potential of the test substance.

2-Propenoic acid, C16-18-alkyl esters (read across)

The Ready Biodegradability (CO2-Evolution) Test to the test substance 2-Propenoic acid, C16-18-alkyl esters was conducted according to the OECD guideline 301B.

The selected test concentration of 20 mg TOC/L corresponds to approximately 26 mg/L test substance. The duration of exposure to the activated sludge was 28 days.Aniline was taken as reference substance.

The test substance was not readily biodegradable in this carbon dioxide evolution test based on the quantitative determination of the formed carbon dioxide in the test substance assays in comparison to the calculated maximal theoretical carbon dioxide production. The required pass level for ready biodegradability was not reached. Because the test substance is a mixture of structure similar compounds the criterion of the ten days window was not applied. Such test substances are multi-component substrates and are typically characterized by different kinetic degradation steps. The degree of biodegradation after an exposure period of 28 days was 50-60 % CO2/ThCO2 in this test. The results in this study are consistent with all validity criteria and the test is valid according to the test guideline of this study. No deviations from the test guidelines or other incidents occurred during the course of the reported test, which may have influenced the results.

 

Dodecyl acrylate (C12) (read across)

A biodegradability test of the read across substance (mixture of CAS no. 2156-97-0 and 21643-42-5) was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The biodegradability was determined in the determination of the biodegradability in the CO2 -Evolution Test performed according to OECD guideline no. 301B. The initial test concentration was 20 mg/L TOC, equivalent to approx. 26 mg/L test substance. The duration of the exposure was 28 days and the test system (inoculum) was activated sludge from the municipal sewage plant Mannheim, Germany. The degree of biodegradation of the test substance was 80 -90 % CO2/ThCO2 after an exposure period of 28 days. That means that the test substance was readily biodegradable under the conditions of this test.

 

Icosyl acrylate (C20) (read across)

A biodegradability test of test substance was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The biodegradability was determined in the determination of the biodegradability in the CO2 -Evolution Test performed according to OECD guideline no. 301B. The initial test concentration was 10 mg/L TOC, equivalent to approx. 13 mg/L test substance. The duration of the exposure was 60 days and the test system (inoculum) was activated sludge from the municipal sewage plant Mannheim, Germany.

The degree of biodegradation of the test substance was 60-70 % CO2/ThCO2 after an exposure period of 60 days. That means that the test substance was biodegradable under the enhanced test conditions of this test.

 

Conclusion

Considering the results of the biodegradation studies to Dodecyl acrylate/ Laurylacrylate (C12), 2-Propenoic acid, C16-18-alkyl esters and Icosyl acrylate/ Behenylacrylate (C20) a weight of evidence approach was made.

Data with the read across substance 2-Propenoic acid, C16-18-alkyl esters revealed biodegradation. Nevertheless, the strict criteria for ready biodegradation were not fulfilled. As the test substance consists of different constituents the 10-day window is not applicable.

To be able to finally conclude on this endpoint additional data form another long chain acrylates were considered. A mixture of C12/C14 acrylates was shown to be clearly readily biodegradable. Acrylates with longer C-chaines (e.g. C20 acrylates ) shown that the test substance is nearly completely degraded after 60 days and can thus be judged to be ready biodegradable, but failing the 10- day window. Such a prolonged test is not available for C16/C18 acrylates, but similar results are expected, as the longer C-chained acrylates represent a worst case in this sense.

Taking all data together, 2-Propenoic acid, docosyl alkyl ester is considered to be biodegradable under the enhanced test conditions.