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

Endpoint summary

Description of key information

Biodegradation: 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).

Adsorption coefficient: Under the chromatographic conditions specified, the test substance eluted as four peaks on the charged aerosol detector (CAD). The corresponding mean adsorption coefficients (Log KOC) for three of the test substance peaks were less than urea (i.e. predicted Log Koc = 0.499) and for the fourth test substance peak was 4.92 (OECD 121 and EU Method C.19).

Additional information

Biodegradation

The key 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.

 

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 mineralisation 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 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.

 

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.

Adsorption coefficient

The key test was performed based on procedures in the OECD Guideline for Testing ofChemicals, 121, Estimation of the Adsorption Coefficient (KOC) on Soil and on Sewage Sludge using HighPerformance Liquid Chromatography (HPLC) and Official Journal of the European CommunitiesNo. L225. Method C.19: Estimation of the Adsorption Coefficient (KOC) on Soil and on Sewage Sludgeusing High Performance Liquid Chromatography (HPLC).

Solutions of test item were prepared in 55 % methanol (MeOH): 45 % ultrapure H2O v/v at nominal concentrations of 75.0 and 100 mg/L. The test substance solutions were prepared from a stock solution in MeOH. Six reference standards were prepared in the respective mobile phase at a nominal concentration range (5.00 to 300 mg/L) selected to provide desired ultraviolet (UV) detector response. Of these reference substances, one was used for dead time determination and the other five had known Log KOC values given in the OECD 121 guideline and were used as calibration standards. The reference standard preparations were sequentially injected into an HPLC system followed by a single injection of each test substance solution. The calibration reference standards injection sequence was repeated following the test substance injections. The HPLC system was operated under standardised isocratic, reverse-phase operating conditions per the guideline.

 

Under the chromatographic conditions specified, the test substance eluted as four peaks on the charged aerosol detector (CAD). The corresponding mean adsorption coefficients (Log Koc) for three of the test substance peaks were less than urea (i.e. predicted Log Koc = 0.499) and for the fourth test substance peak was 4.92.