2-Propenoic acid, 2-hydroxyethyl ester, reaction products with O,O-bis(dialkyalkyl) hydrogen phosphorodithioate and dimethyl phosphonate

Endpoint summary

Description of key information

The test item was determined to be not readily biodegradable becausethe final mean percent biodegradation for the test item was 3.3 % by the end of the test(OECD 301 B and EU Method C.4-C).

Additional information

GUIDELINE

The study protocol was based on the procedures specified in the OECD Guideline for Testing of Chemicals, Method 301B and Commission Directive, Annex V, 92/69/EEC, Method C.4-C, Carbon Dioxide (CO2) Evolution. Tests of ready biodegradability are stringent tests that provide limited opportunity for acclimation and biodegradation to occur.

 

METHODS

In the CO2 test, inoculated mineral medium was dosed with a known amount of test substance as the nominal sole source of organic carbon and aerated with CO2-free air. The CO2 produced from the mineralization of organic carbon within the test chambers was displaced by the flow of CO2-free air and trapped as K2CO3 in KOH trapping solution. The amount of CO2 produced by the test substance (corrected for that evolved by the blank inoculum) is expressed as a percentage of the theoretical amount of CO2 (TCO2) that could have been produced if complete biodegradation of the test substance occurred. The test contained a blank control group, a reference group and a treatment group, each with three replicates and a single toxicity control. The blank control was used to measure the background CO2 production of the inoculum and was not dosed with a carbon source. The reference chambers were dosed with sodium benzoate, a substance known to be biodegradable, at a nominal concentration of 10 mg C/L. The treatment group test chambers were used to evaluate the test item at a nominal concentration of 10 mg C/L. The toxicity control was used to evaluate the toxicity of the test substance to the inoculum and was dosed with both the reference (10 mg C/L) and test substances (10 mg C/L).

 

RESULTS

Results indicated that the activated sludge inoculum was active, degrading the reference substance an average of 88.1 % by the end of the test and that the test substance was not inhibitory to the inoculum at the concentration tested, as the toxicity control exceeded 25 % degradation by Day 14 of the study. The average cumulative percent biodegradation for the test item was 3.3 % by the end of the test.

 

CONCLUSION

Evidence of ready biodegradability in a Carbon Dioxide Evolution Test is 60 % TCO2 within the 28-day test period. In addition, the pass level must be reached within 10 days of achieving 10 % TCO2. The final mean percent biodegradation for the test item was 3.3 % by the end of the test. A negative result in a test of ready biodegradability does not necessarily mean that the test substance will not be biodegradable under relevant environmental conditions, but that additional testing maybe needed. The toxicity control achieved > 25 % degradation by Day 14 and therefore the test item may be considered non-inhibitory at the concentration tested in this study.