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Biodegradation in water: screening tests

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Description of key information

readily biodegradable (OECD guideline 301 B/EU method C.4-C and OECD guideline 301 F/EU method C.4-D; RL1; GLP)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

For the assessment of the biodegradability of MDIPA-Esterquat C16-18 and C18 unsatd. three studies are available, two studies according to OECD guideline 301 B, and one study according to OECD guideline 301 F.

 

The biodegradation of MDIPA-Esterquat C16-18 and C18 unsatd. was investigated over a 28-day period in a CO2 Evolution Test according to EC method C.4-C (92/69/EEC) and OECD guideline 301 B. The test medium was inoculated with microorganisms from a digester of a sewage treatment plant mainly fed with municipal wastewater.

The test substance was added from a stock solution made from an aqueous dispersion (5.28% a.i. w/w) provided by the sponsor.

The test solutions were aerated by the passage of CO2 free air at a controlled rate in closed flasks at 22 °C for 28 days. The rate of degradation was monitored by measuring the carbon dioxide produced over the 28-d period. The amount of carbon dioxide produced by the microbial population during biodegradation of the test item at a concentration of 20 mg/L, corrected for that derived from the blank inoculum run in parallel, was expressed as a percentage of the nominal DOC loading initially present. In order to check the procedure, sodium benzoate was used as a degradable reference item at a concentration of 20 mg/L, along with a toxicity control at 20 mg/L MDIPA-Esterquat C16-18 and C18 unsatd., and 20 mg/L sodium benzoate.

The degradation of MDIPA-Esterquat C16-18 and C18 unsatd. in the static test was found to be 60 % after 28 days. Biodegradation within the 10-day-window was found to be 40 % on the basis of the values obtained by measurement of the trap solutions in the course of the study and calculated to be 50 % assuming that the saturation of CO2 in the media found after acid dissolving at test end is stable after a few days of incubation.

With 40 % after 28 days, a significant abiotic degradation occurred.

The degradation of the reference substance sodium benzoate had reached 100 % within the first 14 days (103 % considering the medium fixed amount). The difference of extremes of replicate values of the removal of the test item at the end of the test is 14 %. Therefore, the test can be considered as valid.

No inhibitory effects of the test item were observed (more than 25% degradation occurred within 14 days) in the toxicity control.

 

The biodegradation of MDIPA-Esterquat C16-18 and C18 unsatd. was investigated over a 28-day period in a CO2 Evolution Test according to EC method C.4-C (2008) and OECD guideline 301 B (1992). The test medium was inoculated with microorganisms from a digester of a sewage treatment plant mainly fed with municipal wastewater.

The test solutions were aerated by the passage of CO2 free air at a controlled rate in closed flasks at 22±2°C for 28 days. The rate of degradation was monitored by measuring the carbon dioxide produced over the 28-d period. The amount of carbon dioxide produced by the microbial population during biodegradation of the test item at a concentration of 17 mg C/L, corrected for that derived from the blank inoculum run in parallel, was expressed as a percentage of the nominal TOC loading initially present. In order to check the procedure, sodium benzoate was used as a degradable reference item at a concentration of 20 mg DOC/L, along with a toxicity control at 17 mg TOC/L test item, and 20 mg DOC/L sodium benzoate.

The biodegradation of the test item was found to be 69% after 28 days. Degradation within the 10-day-window was found to be 36% on the basis of the values obtained by measurement of the trap solutions in the course of the study.

The degradation of the reference substance sodium benzoate had reached 95% within the first 14 days (actually within 11 days). The difference of extremes of replicate values of the removal of the test item at the end of the test is 5%. Therefore, the test can be considered as valid.

No inhibitory effects of the test item were observed (more than 25% degradation occurred within 14 days; 48% after 11 days of incubation) in the toxicity control.

MDIPA-Esterquat C16-18 and C18 unsatd. can be considered as being readily biodegradable but failing the 10-day-window under the test conditions of an OECD 301B test.

 

Although the 10-day window criterion is not fulfilled, the test substance can be regarded as readily biodegradable as it is a UVCB substance representing a complex multi-constituent substance with structurally similar constituents:

1.according to the REACH Guidance on information requirements and chemical safety assessment, Chapter R.7b: Endpoint specific guidance “These pass levels have to be reached in a 10-day window within the 28-day period of the test. The 10-day window does not apply to TG 301 C or if the test substance represents a mixture of homologous compounds e.g. technical surfactants."

2. according to CLP 7th ATP, 4.1.2.9.5.: "These levels of biodegradation must be achieved within 10 days of the start of degradation which point is taken as the time when 10 % of the substance has been degraded, unless the substance is identified as an UVCB or as a complex, multi-constituent substance with structurally similar constituents. In this case, and where there is sufficient justification, the 10-day window condition may be waived and the pass level applied at 28 days."

 

The biodegradation of MDIPA-Esterquat C16-18 and C18 unsatd. was investigated over a 28-day period in a Manometric Respirometry Test according to EC method C.4-D (2008) and OECD guideline 301 F (1992).

The test solutions were stirred in closed flasks at 22°C ± 1°C for 28 days. The rate of degradation was monitored by measuring the quantity of oxygen required to maintain a constant gas volume in the respirometer flasks over a 28-d period. The amount of oxygen taken up by the microbial population during biodegradation of the test item at a concentration of 460 mg/L (ThOD = 60 mg/L), corrected for uptake by the blank inoculum run in parallel, was expressed as a percentage of the ThOD (theoretical oxygen demand). In order to check the procedure, sodium benzoate was used as a degradable reference item at a concentration of 100 mg/L, along with a toxicity control at 460 mg/L test item and 100 mg/L sodium benzoate.

The biodegradation of the test item was found to be at mean 79% with a standard deviation of 6.7 % for a concentration of 460 mg test item per liter after 28 days. Biodegradation within the 10-day-window was found to be 65%. The 10-day-window started at day 2.

The degradation of the reference substance sodium benzoate had reached 85 % within the first 14 days. The difference of extremes of replicate values of the removal of the test item at the end of the test is less than 20%.Therefore, the test can be considered as valid.

The biodegradation of the item mixture in the toxicity control was found to be 75% after 14 days of incubation. Thus, the demanded threshold value of 25% is exceeded and the test item can be identified as non-toxic in a ready biodegradability test.

According to the OECD guideline 301F, MDIPA-Esterquat C16-18 and C18 unsatd. can be considered as being readily biodegradable under the chosen test conditions. 

 

Similar results were also obtained with the closely related source substance MDEA-Esterquat C16-18 and C18 unsatd.: 

The biodegradation of MDEA-Esterquat C16-18 and C18 unsatd. was studied in accordance with the OECD TG 301 B, and in compliance with GLP standards for 28 d. MDEA-Esterquat C16-18 and C18 unsatd. was applied at 2 concentration of 10 and 20 mg/L. CO2 production was analysed at 0, 1, 4, 5, 7, 8, 11, 14, 18, 22, and 28 days of incubation. The two test treatments (10 and 20 mg/L) reached > 60% CO2 production and met the 10 -day window. Therefore MDEA-Esterquat C16-18 and C18 unsatd. fulfills the OECD criteria of ready biodegradability.