Hexamethylene diisocyanate, oligomers, reaction products with 3-methoxypropylamine

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 June 23, 2011 to July 22, 2011

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:

yes

Remarks:

see ''Principle of method if other than guideline''

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

yes

Remarks:

see ''Principle of method if other than guideline''

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

CAS No.: 162492-07-1; Batch No.: 1591ZG-075; Main component: 40 - 75 %; Content (certified): >98 %; Appearance: solid, off-white / cream powder

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Test system: inoculum of the aqueous phase of non adapted activated sludge,
Source: Municipal sewage treatment plant, D-31137 Hildesheim,
Reasons for the selection of the test system: Activated sludge from the sewage plant at Hildesheim is well suited as it receives predominantly municipal sewage and hardly any industrial chemical waste,
Pretreatment: The activated sludge was washed twice with autoclaved tap water. After the second washing the settled sludge was resuspended in mineral salts medium and was maintained in an aerobic condition by aeration for 4 hours. Thereafter the sludge was homogenized with a blender. The supernatant was decanted and maintained in an aerobic condition by aeration with CO2 free air for 5 days. 10 mL/L were used to initiate inoculation,
Colony forming units: approx. 10+E7 – 10+E8 CFU/L in the test vessel.

Duration of test (contact time):

28 d

Initial conc.:

11.2 other: mg C/L

Based on:

TOC

Initial conc.:

20 mg/L

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Functional control: sodium benzoate (Fluka)
Replicates: single
Test concentration: 20 mg/L
ThCO2: 2.13 mg CO2/mg
ThTOC: 0.58 mg C/mg
Carbon content in the vessel: 11.6 mg C/L

Test substance:
Replicates: duplicates
Test concentration: 20 mg/L
TOC: 0.560 mg C/mg
ThCO2: 2.06 mg CO2/mg test item
Carbon content in the vessel: 11.2 mg C/L
Pretreatment: ultrasonic treatment, 15 minutes at room temperature

Toxicity control: test substance and reference substance in test concentration
Replicates: single

Inoculum control: test medium without test and/or reference substance
Replicates: duplicates

Application: once at test start
Test vessels: 5000 mL, brown glass
Volume of the test medium: 3000 mL
Test medium: mineral salts medium acc. to OECD 301 B / CO2 Evolution test 20.0 - 24.0 °C
Dispersion treatment: continuous stirring
Aeration: 30 - 100 mL/min
Photoperiod: low light conditions (brown glass bottles)

Course of the study:

The necessary amounts of bidistilled water, mineral salts medium and inoculum were placed in each of the incubation vessels. The vessels were aerated for 24 hours with CO2 free air. After 24 hours the CO2 adsorption vessels were connected to the air outlets of the incubation vessels via a series of 3 gas wash bottles, each containing 100 mL of a 0.0125 mol/L Ba(OH)2 solution.

Test and reference substance were weighed out. A defined volume of bidistilled water was added to the test substance and was treated with ultrasound. The test substance dispersions and the reference substance were transferred into the incubation vessels. The vessels were made up to 3 L with bidistilled water and connected to the system for the production of CO2 free air.

On day 28, 1 mL 37 % HCl was added to each of the vessels. Aeration was continued for further 24 hours and the quantity of CO2 released was determined.

Reference substance:

benzoic acid, sodium salt

Test performance:

I

Key result

Parameter:

% degradation (CO2 evolution)

Value:

0

Sampling time:

29 d

Details on results:

The adaptation phase of the functional control changed after 2 days into the degradation phase (degradation >10 %). The course of the degradation was rapid and the functional control reached the pass level of 60 % after 6 days. After 18 days the plateau was reached with a biodegradation of 82 %. The validity criterion degradation 60 % after 14 days is fulfilled.

In the toxicity control a biodegradation of 39 % was determined within 14 days and it came to 39 % after 28 days. The biodegradation of the reference substance was not inhibited by the test substance in the toxicity control.

Both test substance replicates did not reach the 10 % level, the biodegradation remained at 0 % until 28 days.

The test substance is classified as not readily biodegradable in the 10-d-window and after 28 days.
In the inoculum control the total CO2 production was 30.3 mg CO2/L after 28 days (validity criterion: < 40 mg CO2/L after 28 days).

CO2-production and biodegradation after 28 days:

CO2-Productionafter 28 d	Functional Control 20 mg/L	Test 20 mg/L No.1	Sub. No. 2	Toxicity Control 20 mg/L Test sub. + 20 mg/L Reference sub.
Net          [mg/3 L]	104.7	0.0	0.5	99.2
[mg/L]	34.9	0.0	0.2	33.1
Theor.     [mg/3 L]	127.8	123.6	123.6	251.4
[mg/L]	42.6	41.2	41.2	83.8
Degradation [%] after 28 d	82	0	0	39

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under the study conditions, biodegradation of the test substance remained at 0% until Day 28, so that it was not considered to be readily biodegradable.

Executive summary:

A study was conducted to evaluate the ready biodegradability of the tests substance according to OECD Guideline 301B (CO2 evolution test) and EU Method C.4 - C, in compliance with GLP. Biodegradation was determined using non-adapted activated sludge over a test period of 28 d. The substance was tested at a concentration of 20 mg/L in duplicate, corresponding to a total organic carbon content (TOC) of 11.2 mg /L in the test vessels. Biodegradation was followed by titrimetric analysis of the quantity of CO2 produced by the respiration of bacteria. Degradation was stopped on Day 28 by acidification of the test solutions. The last titration was made on Day 29, after residual CO2 had been purged from the test solutions over a period of 24 h. The percentage CO2 production was calculated in relation to the theoretical CO2 production (ThCO2) of the test substance. Biodegradation was calculated for each titration time. To check the activity of the test system, sodium benzoate was used as functional control. The percentage degradation of the functional control reached the pass level of 60% after 6 d and the plateau after 18 d, with a biodegradation of 82%. In the toxicity control containing both test and reference substance, a biodegradation of 39% was determined within 14 d, reaching 39% after 28 d. The biodegradation of the reference substance was not inhibited by the test substance in the toxicity control. Under the study conditions, biodegradation of the test substance remained at 0% until Day 28, so that it was not considered to be readily biodegradable (Fiebig, 2011).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

A study was conducted to evaluate the ready biodegradability of the tests substance according to OECD Guideline 301B (CO2 evolution test) and EU Method C.4 - C, in compliance with GLP. Biodegradation was determined using non-adapted activated sludge over a test period of 28 d. The substance was tested at a concentration of 20 mg/L in duplicate, corresponding to a total organic carbon content (TOC) of 11.2 mg /L in the test vessels. Biodegradation was followed by titrimetric analysis of the quantity of CO2 produced by the respiration of bacteria. Degradation was stopped on Day 28 by acidification of the test solutions. The last titration was made on Day 29, after residual CO2 had been purged from the test solutions over a period of 24 h. The percentage CO2 production was calculated in relation to the theoretical CO2 production (ThCO2) of the test substance. Biodegradation was calculated for each titration time. To check the activity of the test system, sodium benzoate was used as functional control. The percentage degradation of the functional control reached the pass level of 60% after 6 d and the plateau after 18 d, with a biodegradation of 82%. In the toxicity control containing both test and reference substance, a biodegradation of 39% was determined within 14 d, reaching 39% after 28 d. The biodegradation of the reference substance was not inhibited by the test substance in the toxicity control. Under the study conditions, biodegradation of the test substance remained at 0% until Day 28, so that it was not considered to be readily biodegradable (Fiebig, 2011).