isostearic acid monoisopropanolamide

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From July 04, 1998 to July 05, 1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch no.: (Lot no.) 9719123G
Appearance (at 20°C): clear liquid, tends to fogging
Carbon content: 73.76 %

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Prior to use, a sample of activated sludge from the sewage plant at Taunusstein-Bleidenstadt was washed twice with the mineral nutrient solution used in this test to eliminate organic components and carbonates from the sludge. After resuspension in the mineral nutrient medium the sludge was aerated by means of compressed humidified air for about four hours. Before use as an inoculum for the C02-evolution-test, the sludge was homogenized in a “Waring Blender” at low speed for 2 minutes and then filtered through a cotton filter which had been carefully rinsed with deionized water. The first 200 mL of filtrate was discarded. The filtrate was used as inoculum (1 % of the final volume of the test solution) on the same day of preparation.

Duration of test (contact time):

28 d

Initial conc.:

>= 10 - <= 20 other: mgTOC/L

Based on:

other:

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

- Study conditions:
The test solutions contained a total volume of 3500 mL: 35 mL of the phosphate mixture solution, 3.5 mL of the calcium chloride solution, 3.5 mL of the magnesium suifate solution, 3.5 mL of the ferric chloride solution, and 354 mL of the inoculum. The test substance was added directly to the test solutions. At time t0, 69 mg of the test substance were given into the first test solution, and 72 mg into the second test solution. The final (calculated) concentration in the first and second test solutions was ca.15 mg TOC/L. For the blank correction, two test solutions were prepared in the same way as the test solutions with the test substance, but without the addition of any test or control substance. At the same time, one test solution containing 120 mg Na-benzoate/3.5L (20 mg TOC2) of test solution was run in parrallel. In the same way, one test solution “toxicity control" containing 120 mg Na-benzoate plus 72 mg test substance/3.5L of test solution was tested in the same way.
Before starting the test, the mineral nutrient solutions with inoculum but without test substance were areated with CO2-free air for 24 h in order to purge the system of CO2. The test solutions were stirred by means of magnetic stirrers in order to distribute the test substance (or control substance) and oxygen in the test solutions at the maximum solubility.
- Performance of the test:
The test was started by addition of the test substance. The gas outlet (exit air line) was connected to three CO2 absorber bottles each filled with 100 mL 0.025 N Ba(OH)2 (connection in series), and bubbling of CO2 free compressed air through the solution was continued. Periodically (if necessary, as explained after) the CO, absorber nearest the test vessel was removed for analysis, and a new CO2 absorber was connected farest the carboy. Precipitation of BaCO3 in the second CO2 trap indicated that the absorber bottle nearest the test vessel had to be changed and analysed for CO2. Titrations were performed at t3d, t6d, t9d, t13d, t19d, t28d and t29d.
- Analytical means:
CO2 generated by the test substance was trapped by 0.025 N Ba(OH)2 in a trap system discribed in the Guideline. Remaining Ba(OH)2 (0.025 N) in the CO2 trap removed from the trap system was titrated with HCl (0.05 N) using phenolphthalein as an indicator. Each HCl mL of difference between the blank control and the test series with the test material titrated corresponds to 1.1 mg of CO2 produced (as indicated in the OECD Test Guideline 301B). For this purpose values of titration for the “blank” (mean values of two parallel blank solutions) were subtracted (CO2 production by the inoculum) from that of the test unit with the test material. Degration was calculated as a percentage of the ‘theoretical CO2 (“%TC02”) that was produced from the organic matter of the test substance by complete combustion. The CO2 being generated was calculated to the nearest 0.01 mg and biodegradation values were rounded up to the nearest full percent. At t28d, 1 mL conc. HCl was given into the test solutions in order to make the dissolved CO2 or inorganic carbon volatile and to purge the system of CO2. Final titrations were made at t29d.

Reference substance:

benzoic acid, sodium salt

Remarks:

to check the activity of the inoculum

Key result

Parameter:

% degradation (CO2 evolution)

Value:

>= 69 - <= 71

Sampling time:

28 d

Remarks on result:

other: ready biodegradability

Details on results:

The final degradation value after 28 days was 70 % (mean value of two parallel test solutions, i.e. 69 and 71%). From the data obtained in the test, the test substance may be regarded as “readily biodegradable”. The “toxicity control” was degraded 79% within 28 days, indicating no bacterial toxicity of the test substance on the activity of the inoculum under the tested conditions. The control substance (Na-benzoate) was degraded 90% within 28 days. The threshold for classification as “readily biodegradable” of < or = 60 % was met within 6d. Thus, the “10-days-window” as required by the OECD Guideline 301B, was met. The CO2 evolution measured in the blank was in the required range. Thus the test was valid.

Results with reference substance:

The control substance (Na-benzoate) was degraded 90% within 28 days.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Under the study conditions, the test substance was considered as readily biodegradable.

Executive summary:

A study was conducted to determine the ready biodegradability of the test substance according to OECD Guideline 301B (CO2 evolution test), in compliance with GLP. The substance was tested in two experiments at a final concentration of ca. 15 mg total organic carbon (TOC)/L for a duration of 28 d. Test and reference substances (positive control: Na-benzoate and toxicity control: test substance plus Na-benzoate) were added to the bottles containing the microbial organisms (activated, domestic sludge) and mineral components, followed by sampling on Days 0, 3, 6, 9, 13, 19, 28 and 29 to measure CO2 evolution. The final mean degradation after 28 d was 70%. The toxicity control was degraded by 79% within 28 d, indicating no toxicity of the test substance to the bacteria of the inoculum. The control substance was degraded 90% within 28 d and the test was considered valid. Under the study conditions, the test substance was readily biodegradable (Springer, 1998).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

A study was conducted to determine the ready biodegradability of the test substance according to OECD Guideline 301B (CO2 evolution test), in compliance with GLP. The substance was tested in two experiments at a final concentration of ca. 15 mg total organic carbon (TOC)/L for a duration of 28 d. Test and reference substances (positive control: Na-benzoate and toxicity control: test substance plus Na-benzoate) were added to the bottles containing the microbial organisms (activated, domestic sludge) and mineral components, followed by sampling on Days 0, 3, 6, 9, 13, 19, 28 and 29 to measure CO2 evolution. The final mean degradation after 28 d was 70%. The toxicity control was degraded by 79% within 28 d, indicating no toxicity of the test substance to the bacteria of the inoculum. The control substance was degraded 90% within 28 d and the test was considered valid. Under the study conditions, the test substance was readily biodegradable (Springer, 1998).