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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The test substance was screened for biodegradation in water according to OECD Guidelines for Testing of Chemicals (1992) No. 301B “Ready Biodegradability; CO2 Evolution Test” references as Method C4-C of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC) and US EPA fate, Transport and Transformation Test Guidelines OPPTS 835.3110 Paragraph (m). 
The test material attained 38 % degradation after 28 days and therefore cannot be considered to be readily biodegradable under test conditions. The test substance is considered as inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

The test substance was screened for biodegradation in water according to OECD Guidelines for Testing of Chemicals (1992) No. 301B “Ready Biodegradability; CO2 Evolution Test” references as Method C4-C of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC) and US EPA fate, Transport and Transformation Test Guidelines OPPTS 835.3110 Paragraph (m).

The total CO2evolution in the control vessels on Day 28 was 29.12 mg/L and therefore satisfied the validation criterion given in the OECD Test Guidelines. 

The IC/TC ratio of the test material suspension in the mineral medium at the start of the test was below 5 % and hence satisfied the validation criterion given in the OECD Test Guidelines.

The difference between the values for CO2 production at the end of the test for the replicate vessels was < 20 % and hence satisfied the validation criterion given in the OECD Test Guidelines.

The test material attained 38 % degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of the OECD Guideline No. 301B.

The toxicity control attained 31 % degradation after 14 days and 40 % degradation after 28 days thereby confirming that the test material was not toxic to the sewage treatment microorganisms used in the test.

Inorganic carbon analysis of the samples from the second absorber vessels on Day 29 confirmed that no significant carry-over of CO2 into the second absorber vessels occurred.

Analysis of the test media from the test material culture vessels of Days 0 and 28 for Dissolved Organic Carbon (DOC) gave percentage degradation values of 46 % and 46 % respectively for the test material replicates R1 and R2, and 47 % for the toxicity control. Sodium benzoate attained 94 % and 95 % degradation respectively for replicates R1 and R2 calculated from the results of the DOC analyses. The degradation rates calculated from the results of the DOC analysis were higher than those calculated from inorganic carbon analysis. This was considered to be due to incorporation test material/sodium benzoate into the microbial biomass prior to degradation, and hence CO2 evolution occurring.