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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From Sep. 18, 1987 to Oct. 16, 1987
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
not specified
Remarks:
Toxicity control
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Bergen County, New Jersey, MUA
- Laboratory culture: Yes
- Dilution water: Standard dilution water
- Duration: 28 d
- Test concentrations: 2 mg/L
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test temperature: 20 ± 1 °C


TEST SYSTEM
- Measuring equipment: YSI Dissolved Oxygen Analyzer 54A
- Number of culture flasks/concentration: Two


SAMPLING
- Sampling frequency: 0, 5, 15 and 28 d


CONTROL AND BLANK SYSTEM
- Oxygen blank: Dilution water without inoculum
- Inoculum blank: Dilution water + inoculum
- Reference (aniline, 2 mg/L) + inoculum
Reference substance:
aniline
Remarks:
2 mg/L
Preliminary study:
No data
Test performance:
No data
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
5 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
15 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
13.7
Sampling time:
28 d
Details on results:
- Oxygen depletion (mg O2/L) for the test item with inoculum was observed to be 1, 1.6 and 2.2 on Days 5, 15 and 28
- Theoretical oxygen demand (TOD) of the test material: 2.56
Results with reference substance:
Theoretical oxygen demand (TOD): 3.09
% degradation: 42, 73 and 95 on Days 5, 15 and 28, respectively
Validity criteria fulfilled:
not specified
Remarks:
Toxicity control
Interpretation of results:
not readily biodegradable
Conclusions:
Under the test conditions (OECD 301D-Closed Bottle Test), the test material was found to be not readily biodegradable.
Executive summary:

A study was performed to evaluate the ready biodegradability of the test material according to OECD Guideline 301 D (closed bottle test), in compliance with GLP. Test substance (2 mg/L) with the standard nutrient medium was kept in sealed Biological Oxygen Demand (BOD) bottles (darkened glass) at 20 ± 1°C for 28 d. BOD dilution water (oxygen blank), inoculated BOD dilution water (inoculum blank) and the reference material (aniline, 2 mg/L) in inoculated BOD dilution water (procedure control) were run in parallel for validation purposes. Dissolved oxygen concentrations (DOC) for each test medium were determined, in duplicate, on Days 0, 5, 15 and 28 by means of a YSI Dissolved Oxygen Analyzer.The % degradation of the reference material on Days 5, 15 and 28 was 42, 73 and 95, respectively. The % degradation of the test material on Days 5, 15 and 28 was 0, 0 and 13.7, respectively. Under the study conditions, the test substance was not readily biodegradable (Drozdowski, 1988). Under the test conditions, the test material was found to be not readily biodegradable.

Description of key information

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information

A study was performed to evaluate the ready biodegradability of the test material according to OECD Guideline 301 D (closed bottle test), in compliance with GLP. Test substance (2 mg/L) with the standard nutrient medium was kept in sealed Biological Oxygen Demand (BOD) bottles (darkened glass) at 20 ± 1°C for 28 d. BOD dilution water (oxygen blank), inoculated BOD dilution water (inoculum blank) and the reference material (aniline, 2 mg/L) in inoculated BOD dilution water (procedure control) were run in parallel for validation purposes. Dissolved oxygen concentrations (DOC) for each test medium were determined, in duplicate, on Days 0, 5, 15 and 28 by means of a YSI Dissolved Oxygen Analyzer. The % degradation of the reference material on Days 5, 15 and 28 was 42, 73 and 95, respectively. The % degradation of the test material on Days 5, 15 and 28 was 0, 0 and 13.7, respectively. Under the study conditions, the test substance was not readily biodegradable (Drozdowski, 1988).

As shown in Section 4.1.1, the substance hydrolyses rapidly in the aquatic environment to form an insoluble urea and potentially a polyurea.Under certain conditions (i.e. high dispersion and low concentrations), tetramethyl-m-xylylene diamine may also be formed. According to the results of BIOWIN v 4.10, urea is not expected to be readily biodegradable. WSKOW v 1.41 and KOCWIN v 2.00 further indicate that it has low solubility in water (0.7 mg/L), an estimated log Kow of 3.53 and an estimated log Koc of 6.27, suggesting that it will tend to partition out of water and bind to sediment or soil, but will not bioaccumulate in organisms. Based on results from biodegradation modelling, tetramethyl-m-xylylene diamine is not expected to be persistent in water, with a half-life from the BIOWIN 2000 Ultimate Survey Model estimated to be 37.5 d (Environment Canada/Health Canada, 2008).

References

Environment Canada/Health(2008). Screening assessment for the challenge. Benzene, 1,3-bis(1-isocyanato-1-methylethyl)-(tetramethyl-m-xylylene diisocyanate). Chemical Abstracts Service Registry Number 2778-42-9. https://www.ec.gc.ca/ese-ees/9C2F9934-38D3-4940-A472-5DD238B6076D/batch2_2778-42-9_en.pdf.