Hexane, 1,6-diisocyanato-, homopolymer, 2-hydroxyethyl acrylate- and propylene glycol monoacrylate-blocked

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 15, 2016 to January 11, 2017

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 ''Any other information on materials and methods"

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

see "Any other information on materials and methods"

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Specification:
Activated sludge from a biologic sewage treatment plant was used. The chosen plant is treating mostly domestic sewage.
Source:
The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf.
Pre-Treatment:
The sludge was filtrated, washed with tap water (2x), then washed with and resuspended in test medium. It was then aerated until use. The dry matter was determined with 3600 mg suspended solids/L.
Activated sludge was used as inoculum (concentration in the test 25.0 mg dry matter/L).

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

other: TOC/L

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Preparations
The medium was prepared from the stock solutions. The stock solution of the positive control was prepared and its DOC was measured. The inoculum was taken from its source, washed, aerated and the dry matter was determined. The test vessels were filled with medium and inoculum. Then, all flasks were aerated for 72 hours with purified, CO2-free, moistened air to purge the system of CO2. On the day of the start of the test, CO2-free medium and inoculum was filled into the test flask.
Sampling
From each front scrubber flask, 10 samples were taken in order to determine the emitted CO2 (on day 0, 2, 4, 7, 9, 11, 14, 18, 23 and 29). The sample volume was 1 mL. The resulting change in the volume of the front flask was considered in the calculation of emitted CO2. On day 28, 5 mL HCl 2 M was added to each test flask in order to drive off dissolved CO2. On day 29, samples from both scrubber flasks were taken.
CO2 Determination
Analyses of the emitted CO2 were made by IC measurement using the carbon analyser TOC multi N/C 2100S, Analytik Jena. Each sample was measured in duplicate or triplicate, respectively (depending on the variation between the measured values). The carbon analyser was calibrated with freshly prepared reference solutions containing potassium hydrogen phthalate (TC), sodium hydrogen carbonate and sodium carbonate (IC) every month. After every start, quality control samples were measured.

Reference substance:

aniline

Test performance:

Inoculum concentration: 25.0 mg/L
Temperature: 18.9 – 23.4°C
pH: 7.1-7.3
abiotic control pH: 6.7

Key result

Parameter:

% degradation (CO2 evolution)

Value:

13

Sampling time:

29 d

Details on results:

- The degree of biodegradation reached 13% after 28 d.
- Since the degradation missed the pass level of 60% within 28 d, the test substance is considered as “not readily biodegradable within 28 d”.
- The abiotic degradation reached 2%.

Results with reference substance:

Degradation behaviour of the positive control and the toxicity control was within the acceptable range.

If degradation in the toxicity flask is below 25% after 14 d, the test substance can be considered as toxic towards the inoculum. As degradation in the toxicity flask was 43% after 14 d, the test substance can be considered as “not toxic towards the inoculum at a concentration of 35.9 mg/L”.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Under the study conditions, the test substance was not considered to be readily biodegradable.

Executive summary:

A study was conducted to evaluate the ready biodegradability of the test substance according to OECD Guideline 301B (CO2 evolution test) and EU Method C.4 - C, in compliance with GLP. This study was performed during a 28 d period using a nominal test substance concentration of 20 mg organic carbon/L (corresponding to 35.7 mg test substance/L). The inoculum used was an activated sludge collected from a domestic sewage treatment plant (adaptation not specified). The test substance was inoculated in a mineral medium and incubated under aerobic conditions in the dark. The amount of DOC in the test solution due to the inoculum was kept as low as possible compared with the amount of organic carbon due to the test substance. Degradation was followed by determining the carbon dioxide produced with a TOC analyser. Measurements were taken at sufficiently frequent intervals to allow the identification of the beginning and end of biodegradation. The degree of biodegradation of the test substance reached 13% after 28 d. Under the study conditions, the test substance was not considered to be readily biodegradable (Muckle, 2017).

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 test substance according to OECD Guideline 301B (CO2 evolution test) and EU Method C.4 - C, in compliance with GLP. This study was performed during a 28 d period using a nominal test substance concentration of 20 mg organic carbon/L (corresponding to 35.7 mg/L). The inoculum used was an activated sludge collected from a domestic sewage treatment plant (adaptation not specified). The test substance was inoculated in a mineral medium and incubated under aerobic conditions in the dark. The amount of DOC in the test solution due to the inoculum was kept as low as possible compared with the amount of organic carbon due to the test substance. Degradation was followed by determining the carbon dioxide produced with a TOC analyser. Measurements were taken at sufficiently frequent intervals to allow the identification of the beginning and end of biodegradation. The degree of biodegradation of the test substance reached 13% after 28 d. Under the study conditions, the test substance was not considered to be readily biodegradable (Muckle, 2017).