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EC number: 237-235-5 | CAS number: 13703-82-7
The reference material (sodium benzoat) is to 80% biodegradated after the test period of 28 days. The corrected value for the biodegradation of the reference material which includes any carry-over of CO2 detected in the CO2 absorber of the second vessel is 70%.
The total CO2 evolution in the inoculum control vessels on Day 28 was 28.86 mg/L. The IC content of the test item suspension in the mineral medium at the start of the test was below 5% of the TC content. The difference between the values for CO2 production at the end of the test for the replicate vessels was <20%.
Altogether, those findings fulfill the validation criterions given in the OECD Test Guidelines.
Acidification of the test vessels on day 28 followed by the final analyses on day 29 was conducted according to the methods specified in the Test Guidelines. This acidification effectively kills the micro-organisms present and drives off any dissolved CO2 present in the test vessels. Therefore, any additional CO2 detected in the day 29 samples originated from dissolved CO2 that was present in the test vessels on day 28. Hence, the biodegradation value calculated from the day 29 analyses is taken as being the final biodegradation value for the test substance. The test item attained 4% biodegradation after 28 days.
The results obtained from the mineral oil vessels showed 37% degradation over the test period. Correction of the biodegradation rate of the test item for mineral oil degradation showed that the test item achieved 0% biodegradation after 28 days.
The toxicity control attained 40% biodegradation after 14 days and 38% biodegradation after 28 days thereby confirming that the test item did not exhibit an inhibitory effect on the sewage treatment micro-organisms used in the test. The slight decrease in biodegradation between days 14 and 28 was considered to be due to sampling/analytical variation.
Sodium benzoate attained 84% biodegradation after 14 days and 70% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions. The slight decrease in biodegradation between days 14 and 28 was considered to be due to sampling/analytical variation.
Table 1: Inorganic Carbon Values on Each Analysis Occasion.
R1, R2: replicates 1 and 2; Abs: CO2 absorber vessels; *: Result from re-analysis of sample.
Table 2: Percentage Biodegradation Values.
* Day 29 values corrected to include any carry-over of CO2 detected in Absorber 2.
A 28 day study was performed to assess the ready bioavailability of the test substance in an aerobic aquaeous medium. The method followed the OECD Guidelines for Testing of Chemicals (1992) No. 301B, "Ready Biodegradability; CO2 Evolution Test" referenced as Method C.4-C of Commission Regulation (EC) No. 440/2008 and US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3110 (Paragraph (m)) and was conducted in compliance with GLP criteria. For the test, non-adapted activated sludge was taken from a wastewater treatment plant which predominantly treats domestic sewage. Due to the fact that the test substance was insolubility in water, preliminary work determined that the best testable dispersion was obtained when the solvent on filter paper method was applied. As reference substance, sodium benzoate was used as procedure control. To assure consistancy between test and procedure control vessels, one filter paper with chloroform evaporarted to dryness was added to each procedure control. Also, additional vessels containing mineral oil at the same concentration as the test substance were prepared. Although the mineral oil was dispered in water directly, it was applied with a filter paper with chloroform evaporated to dryness, as well, to maintain consistancy. All samples were analyzed for IC using either Shimadzu TOC-VCPH TOC analyzer or a Shimadzu TOC-LCSH TOC analyzer immediately after they were taken.
All validation criteria given by the OECD Test Guidelines are fulfilled.
The test substance attained 4% biodegradation after 28 days. The results obtained from the mineral oil vessels showed 37% degradation over the test period. Correction of the biodegradation rate of the test substance for mineral oil degradation showed that the test substance achieved 0% biodegradation after 28 days. The test substance therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.
Biodegradation screening test, OECD 301B, aerobic, activated sludge: 4% degradation (CO2 evolution) after 28 days, not readily biodegradable
A 28 day study key study (Bayliss, 2016) was performed to assess the ready bioavailability of the test substance in an aerobic aquaeous medium. The method followed the OECD Guidelines for Testing of Chemicals (1992) No. 301B, "Ready Biodegradability; CO2 Evolution Test" referenced as Method C.4-C of Commission Regulation (EC) No. 440/2008 and US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3110 (Paragraph (m)) and was conducted in compliance with GLP criteria.
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