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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002-08-26 to 2002-10-23
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Deviations:
yes
Remarks:
After 19 days, the BOD curve of bottle 1 went down for sveral hours. It was judged that this trouble did not affect the reliability of the test results, because the BOD curve of bottle 1 was restored shortly after.
Principles of method if other than guideline:
After 19 days, the BOD curve of bottle 1 went down for sveral hours. This accident was considered to be caused by momentary troubles in the measuring part of the closed system oxygen consumption measuring apparatus. It was judged that this trouble did not affect the reliability of the test results, because the BOD curve of bottle 1 was restored shortly after and no deviation occured in any of the other bottles.
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Analytical purity: 99.0% (based on GC-IS)
- Source and lot/batch No.of test material: ZR023979G3G631
- Expiration date of the lot/batch: not reported
- Purity test date: not reported

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: in a desiccator under light shielding
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source: Chemical Evaluation and Research Institute, Japan
- Storage conditions: Not reported
- Preparation of inoculum for exposure: Not reported
- Pretreatment: Not reported
- Concentration of sludge: The concentration of suspended solids was determined to be 4.4 g/L in the concentrated sludge.
- Water filtered: Not reported
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: basal medium (composition not reported)
- Test temperature: 25 +/-1 °C
- pH:
pH at t=0: 7.0-8.2
pH at t=28d: 7.3-8.3
- pH adjusted: no

TEST SYSTEM
- test volume: 300 mL
- Concentration:
*test substance (bottles 3-6): 100 mg/L
*aniline (bottle 1): 100 mg/L
*activated sludge (bottles 1-5): 30 mg/L
- Test bottle contents:
* Bottle 1 aniline + activated sludge + basal medium (29 µL (30 mg) of aniline was added to the basal medium, with the total volume of the basal medium and the sludge fixed at 300 mL, then activated sludge was added.)
* Bottle 2 activated sludge + basal medium (activated sludge was added to the basal medium with the total volume of the basal medium and the sludge fixed at 300 mL)
* Bottles 3-5 test substance + activated sludge + basal medium (30 mg of the test substance was added to the basal medium, with the total volume of the basal medium and the sludge fixed at 300 mL, then activated sludge was added.)
* Bottle 6 test substance + purified water (30 mg of the test substance was added to 300 mL of purified water)
- Number of culture flasks/concentration:
* test substance and inoculum: 3 replicates
* inoculum blank: 1 replicate
* positive control: 1 replicate
* toxicity control: 1 replicate
- BOD measurement
* apparatus: closed system oxygen consumption measuring apparatus. Ohkura Electric Co., Model OM-2001 (M.S.I. ID No. E)
- pH measurement
* After the exposure period, 20 mL of the test solution in each test bottle was transferred into a 20-mL glass beaker for pH measurement.
* After pH measurement, the test solution was returned to each bottle for measurement of residual test substance concentration.
* apparatus: pH meter, ORION Research, Model 720A
- DOC measurement
* apparatus: TOC analyser, Shimadzu Co, model TOC-5000A
* conditions: Furnace temperature: 680 °C
Air flow rate: 150 mL/min
Sensitivity: x 5
Injection volume: 50 µL
Repeated number: n=3
* calibration curve: The following standard solutions were injected in the TOC analayzer. The calibration curve was prepared by the data processor of the analyser.
Standard solutions:
TC (total carbon) 20 and 50 mg C/L aqueous solutions of potassium biphthalate.
IC (inorganic carbon) 0 mg C/L purified water (purified by Milli-Q) and 10 mg C/L aqueous solution of sodium hydrogen carbonate and sodium carbonate.
*Measurement of DOC in bottles
10 mL of the test solution in each bottle was transferred into a 10-mL centrifuge tube and centrifuged at 3000 rpm for 10 minutes. Five millilitre of supernatant was used for DOC measurement. The remaining supernatant and the precipitate were returned to each bottle for the measurement of the residual test substance concentration.
- .

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 1 replicate with only inoculum
- Toxicity control: yes, 1 replicate with test item, reference substance, and inoculum
- Positive control: yes, 1 replicate with reference item and inoculum

STATISTICAL METHODS
Equations for calculation of degradability based on BOD, DOC, and residual test substance concentration are as follows:
-Degradability based on BOD
*Degradability (%) = (BODs-BODb)/ThOD x 100
BODs = oxygen consumption (mg) in bottles 1, 3, 4 and 5
BODb = oxygen consumption (mg) in bottle 2
ThOD = theoretical oxygen demand (mg) of aniline and the test substance
*ThOD
Aniline: C6H7N + 35/4O2 -> 6CO2 + 7/2 H2O + NO2
ThOD = 90.2 mg O2 / 30 mg of aniline
Test substance: C14H14ON2Cl2 + 19O2 -> 14CO2 + 7H2O + 2NO2 + 2Cl
ThoD = 61.4 mg O2 / 30 mg of the test substance
-Degradability based on DOC
Degradability (%) = (1 – (DOCs – DOCb)/DOCc x 100
DOCs = DOC (mg/L) in bottles 3, 4, and 5
DOCb = DOC (mg/L) in bottles 2
DOCc = DOC (mg/L) in bottles 6
-Degradability based on residual test substance concentration
Degradability (%) = (1 – Cs/Cc) x 100
Cs = concentration (mg/L) in bottles 3, 4, and 5
Cc = concentration (mg/L) in bottle 6
Reference substance:
aniline
Remarks:
Batch No. 403F1767
Test performance:
The positive control substance was degraded at least 40 % (54%) within 7 days.
Key result
Parameter:
% degradation (O2 consumption)
Value:
ca. 1
Sampling time:
28 d
Remarks on result:
other: mean of test bottle 3, 4 and 5
Parameter:
% degradation (DOC removal)
Value:
ca. 0.7
Sampling time:
28 d
Remarks on result:
other: mean of test bottle 3, 4 and 5
Parameter:
% degradation (test mat. analysis)
Value:
ca. 0.3
Sampling time:
28 d
Remarks on result:
other: mean of test bottle 3, 4 and 5
Details on results:
The criterion for ready biodegradability (at least 60% biodegradation after 28 days) was not met.
Results with reference substance:
The positive control item aniline was biodegraded by 54% within 7 days (>40%), confirming suitability of the activated sludge.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
A 28-d ready biodegradability test (OECD 301C, modified MITI test) using activated sludge indicated that the test substance was not readily biodegradable under the conditions of the test (initial concentration 100 mg/L). The test substance showed 0%, 2% and 1% biodegradation (test bottle 3, 4 and 5, respectively, based on % O2 consumption). From the degradability results based on the BOD, DOC and the residual test substance concentration, it is concluded that the test substance was not readily biodegradable and was not transformed under the conditions of the test. The results of the test can be considered reliable without restriction.
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Data from the related substance imazalil base is used to cover this endpoint. The justification for read across is attached in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
Key result
Parameter:
% degradation (O2 consumption)
Value:
ca. 1
Sampling time:
28 d
Remarks on result:
other: mean of test bottle 3, 4 and 5
Parameter:
% degradation (DOC removal)
Value:
0.7
Sampling time:
28 d
Remarks on result:
other: mean of test bottle 3, 4 and 5
Parameter:
% degradation (test mat. analysis)
Value:
0.3
Sampling time:
28 d
Remarks on result:
other: mean of test bottle 3, 4 and 5
Details on results:
The criterion for ready biodegradability (at least 60% biodegradation after 28 days) was not met.
Interpretation of results:
not readily biodegradable
Conclusions:
A 28-d ready biodegradability test (OECD 301C, modified MITI test) using activated sludge indicated that the test substance was not readily biodegradable under the conditions of the test (initial concentration 100 mg/L). The test substance showed 0%, 2% and 1% biodegradation (test bottle 3, 4 and 5, respectively, based on % O2 consumption). From the degradability results based on the BOD, DOC and the residual test substance concentration, it is concluded that the test substance was not readily biodegradable and was not transformed under the conditions of the test. The results of the test can be considered reliable without restriction.

Description of key information

No study was available on the biodegradation of the test substance imazalil sulfate in water. Therefore, read across is performed using a study from the related substance imazalil. The study by Koyasu (2002) was considered as the key study to cover this endpoint (Klimisch 1). The biodegradability source substance was determined according to OECD Guideline 301C. Under the conditions of the test, the source substance was determined to be not biodegradable within 28 days.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information