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Biodegradation in water: screening tests

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Description of key information

In a dissolved organic carbon test according to OECD TG 301A ureido methacrylate reaches the pass level of 70%  in the 10-d  windows. Therefore it is regearded as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The OECD 301-A (DOC die-away BASF 2012) study was taken as key study. This actual study allows a differentiated conclusion about the biodegradation as the conducted study on Inherent Biodegradability. The required degree of biodegradation within the 10-d window was obtained.

Key study (ready biodegradability):

A study was conducted according to OECD TG 301A, Regulation (EC) No 440/2008 method C.4-A and OPPTS 835.3110. Ureido methacrylate was supplied as an aqueous solution (50% wlv). The DOC die Away test was performed in 2L conical flaks equipped with baffles to optimize the insertion of oxygen. Municipal activated sludge from the wastewater treatment plant from the aeration tank of the plant was used and aerated in the laboratory until use. The used volume for the test assays was 1000 mL. Two blanc control vessels containing mineral salts medium, the substance assays contain the test substance with a concentration of 20 mg/L DOC, two reference substance assay (RS) contains aniline with a concentration of 20 mg/L DOC, an assay for inhibition control(IH) contains the test substance and the reference substance in the same concentration in relation to its dissolved organic carbon contents,.the test of physical chemical elimination (PC) and test assay of adsorption control (AC) containing mg/L mercury chloride was prepared with test substance in the concentration of 20 mg/L DOC. For aeration the test vessels were shaken at a temperature of 22 ± 2°C using an orbital shaker. The DOC measurement was performed twice per week, these DOC-values were compared with the values from begin of exposure. The decrease of DOC concentration was expressed as biodegradation degree and plotted by a biodegradation curve. The required pass of 70% at 10-d window for the ready biodegradability was reached. At the end of exposure after 28 days the degree of biodegradation was 90-100 % expressed as removal of DOC. The results in this study are consistent with all validity criteria and the test is valid according to the guideline. Thus Ureido methacrylate is regarded as readily biodegradable.

Supporting study (inherent biodegradability):

The inherent biodegradability of ureido methacrylate was assessed by a Manometric Respirometry procedure based on OECD Procedure 302C (Inherent Biodegradability, Modified MITI (II) test) but included features of OECD Procedure 301F (Ready Biodegradability, Manometric Respirometry test). Ureido methacrylate was supplied as an aqueous solution (50% wlv). An allowance was made for its water content during the preparation of test mixtures. Two test flasks contained mineral salts medium, inoculated with activated sludge (100 mg solids/litre), and ureido methacrylate at a nominal concentration of 59.8 mg as ureido methacrylate/L (equivalent to a ThODammonia of 50.7 mgO2/flask). An abiotic-control contained ultrapure water alone and ureido methacrylate (59.8 mg/L) and an abiotic-blank comprised ultrapure water alone. Two blank-control cultures contained inoculated mineral salts medium alone and a positive control contained inoculated mineral salts medium plus the reference substance sodium benzoate (100 mg/L). The potential inhibitory effect of ureido methacrylate on the degradative activity of the microbial inoculum was assessed by examining the rate and extent of degradation of sodium benzoate (100 mg/L) in its presence (59.8 mg/L). The contents of the flasks were vigorously stirred to give a vortex depth of approximately 2 cm. Each flask was fitted with a trap that contained a carbon dioxide absorbing solution and a manometer that contained an electrolyte. Oxygen consumed during biodegradation caused a change in the level of electrolyte in the manometer and this caused a demand for oxygen, which was produced at an electrode. The cumulative level of oxygen demanded was logged automatically and the cumulative level expressed as a percentage of the ThOD of the mixture.

Sodium benzoate had been degraded by 66.2% of the ThOD of the mixture (91.9 mgO2) after 4 days of incubation and had achieved, at most, 77.7% after 28 days. In the presence of ureido methacrylate, degradation of sodium benzoate had achieved 61.6% by 3 days and, at most, 76.6% by the end of the test on Day 28. Cumulative oxygen consumption in the controls after 28 days (20.8 mgO2) was considered to be acceptable for this assay system. These results confirm that ureido methacrylate was not inhibitory to the activity of the microbial inoculum and that the test was valid.

Biodegradation of ureido methacrylate had achieved 15% after approximately 6 days of incubation, 70% by Day 15 and had reached, at most, 84.8% by Day 28. The level of degradation of ureido methacrylate that was calculated assuming that nitrogen was oxidised to nitrite or nitrate was approximately 60% on Days 18 and 24, respectively; by the end of the test on Day 28, degradation had achieved, at most, 64.7% and 60.0% of the ThODnitrite and ThODnitrate values, respectively.

Abiotic degradation of ureido methacrylate was negligible (equivalent to 2.4% of its ThODammonia). Substances that achieve 260% degradation in this type of test are generally considered to show evidence of inherent, ultimate degradation. Ureido methacrylate can be considered to be inherently, ultimately degraded using this criterion (Huntingdon, 2002).

Supporting study( biodegradation):

The biodegradability of ureido methacrylate exposed to microorganisms derived from activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions. The biodegradability of based on O2 consumption was calculated to be 63 % after 28 days as compared to the theoretical O2 demand (ThOD). The biodégradation of reached 27 % at the end of the 10-d window. Significant biodegradation of the test substance was observed after a lag phase of about 1 day. The procedure control sodium benzoate reached 84 % biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.

The calculated biodegradation based on DOC measurement reached 70 % for ureido methacrylate and 99 % for sodium benzoate. The data show that the consumed O2 was used for almost complete mineralization of the test compound, since the determined degradation values based on BOD were within the same range than those based on DOC. Ureido methacrylate did not reach the pass level of 60 % for ready biodegradability in the Manometric Respirometry Test within the 10-d window and, therefore, cannot be termed as readily biodegradable. However, the pass level of 60 % was reached after about 27 days of Incubation (Röhm, 1999).

Supporting study

Determination of the ready biodegradability of the test item: HYDROXYETHYLIMIDAZOLIDONE METHACRYLA TE, according to the procedure described in Appendix C.4-D of EEC -directive 92/69, and OECD Guideline 301 F (adopted on 17/07/92). Under the test conditions, the percentage of biodegradation of HYDROXYETHYLIMIDAZOLIDONE METHACRYLATE reached 78% within 26 days (plateau) and 79% at the end of the test (28 days). (Arkema, 2005)

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