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Biodegradation in water: screening tests

Description of key information

The experiment was performed to assess the inherent biodegradability of the test item in an aerobic aqueous media.
An experiment of ready biodegradability was also performed to determine the biodegradation of FAT 65088/A TE.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

1) The study was performed to assess the inherent biodegradability of the test item in an aerobic aqueous media. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1992) No. 302B, “Inherent Biodegradability; Modified Zahn-Wellens/EMPA Test”, Method C.9 of Commission Regulation (EC) No. 440/2008, and the US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3200.

 

Methods:

The test item was exposed to activated sewage sludge micro-organisms at a concentration of 100 mg carbon/L with mineral medium in the dark at temperatures of between 20 and 24 ºC for 28 days. The biodegradation of the test item was assessed by the determination of dissolved organic carbon removal. Control cultures with inoculum and the reference item, diethylene glycol, together with a toxicity control were used for validation purposes.

 Results:

The test item attained 11% biodegradation after 28 days.

 The test item can therefore be considered not to have exhibited evidence of inherent, primary biodegradation under the experimental conditions employed in this study.

2) The ready biodegradability study, of the test item in an aerobic aqueous medium, was performed. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1992) No. 301B, "Ready Biodegradability; CO₂Evolution

Methods…….

An initial experiment was conducted at a concentration of 10 mg C/L. The toxicity control vessel, containing both the test item and sodium benzoate, attained less than 25% biodegradation after 14 days. These results indicated that, under the strict terms and conditions of the OECD Guidelines, the test item would be classed as exhibiting inhibitory effects.

 

Therefore, following the recommendations of the Test Guidelines, in the definitive test, the test item at a reduced concentration of 5 mg C/L was exposed to activated sewage sludge micro-organisms with culture medium in sealed culture vessels in the dark at approximately 21°C for 28 days.

 

The biodegradation of the test item was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes.

 

Results…….

The test item attained 0% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.