1-[2-fluoro-6-(trifluoromethyl)benzyl]-5-iodo-6-methylpyrimidine-2,4(1H,3H)-dione

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

31st May 2018 to 2nd July 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: MEP, P.R. China, the Guidelines for the Testing of Chemicals, Degradation and Accumulation (2nd edition), No. 301F 'Manometric Respirometry' (2013.9)

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: Shenyang North Sewage Treatment Plant 4

Preparation of inoculum for exposure:
- Pretreatment: Coarse particles were removed by filtration through a fine sieve and the sample was settled. After the supernatant was discarded, the sludge was washed twice with mineral medium and the concentrated sludge sludge was suspended in mineral medium. 3 replicates of 10ml suspended sludge were weighed and dried at 105 0C for 2 hours minutes and reweighed to calculate initial sludge concentration. The measured concentration of suspended sludge was 10.31g/L as SS and was prepared with mineral medium to yield a concentration of 4.0g/L as SS. The suspended sludge was kept aerobic at 21.9 - 23.4 oC until the day of the test.

- Preparation of Inoculum: On the day of the test, 5 replicates of 10ml suspended sludge was weighed and dried at 105oC for 1.5 hours and reweighed to calculate initial sludge concentration. The measured concentration of suspended sludge was 3438mg/L as SS.

Duration of test (contact time):

28 d

Initial conc.:

53.12 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
Stock Solution A: 4.2569g of KH2PO4, 10.88732g of K2HPO4, 16.70110g of Na2HPO4 . 2H2O and 0.25143g NH4Cl added to distilled water and made up to 500ml
Stock Solution B: 3.64398g CaCl2 . 2H2O added to distilled water and made up to 100ml
Stock Solution C: 2.25031g MgSO4 . 7H2O added to distilled water and made up to 100ml
Stock Solution D: 0.02517g FeCl3 . 6H2O added to distilled water and made up to 100ml.
To prepare 1L of mineral medium, 10ml of Stock Solution A was added to 800ml of distilled water, stirred and 1ml each of Stock Solutions B, C and D added. The mixture was then made up to 1L with distilled water.

- Preparation of inoculated mineral medium: 800ml mineral medium was placed in a 1L flask and 8.7ml of prepared activated sludge added and the mixture made up to volume to give a suspended sludge concentration of 30mg/L

- Test temperature: 22 ± 1oC
Light: Diffused light

TEST SYSTEM
- Culturing apparatus: 1L flasks
- Number of culture flasks/concentration: 2
- Measuring equipment: Automated Respirator CES UK Ltd

SAMPLING
- Sampling frequency: 24 hr intervals for 28 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: Test vessels containing inoculated mineral medium only were prepared in duplicate.
- Abiotic sterile control: 0.06072g of the test item was weighed into the test flask and 900ml of mineral medium was added. 100ml of 3,5-DCP was added, final concentration 50mg/L. The concentration of the test item was 60.72 mg/L (equivalent to 52.22 mg/|L ThOD NH3) No inoculums were added to the test vessel. One replicate was sufficient.
- Toxicity control: 0.06212g of test item and 0.03057g of reference item were weighed and added to a test vessel. The concentration of the test item was of 62.12 mg/L (equivalent to 53.42 mg/L as ThODNH3), and the reference item was 30.57 mg/L of sodium benzoate (equivalent to 51.05 mg/L as ThODNH3), The concentration expressed as the sum of ThODNH3 was 104.47 mg/L. One replicate was sufficient.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

8.6

Sampling time:

28 d

Results with reference substance:

Biodegradation of Sodium Benzoate reached 64.2% after Day 5 and 95.3% after Day 14

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Based on the results, the test item Methyl iodouracil is not 'readily biodegradable' under the described test conditions. 

Executive summary:

The ready biodegradability test of Methyl iodouracil was conducted with unacclimatised sewage micro-organisms by measuring oxygen consumption over the 28 day test period. 

The test item was added directly to test vessels at a level of 61.77 mg/L (equivalent to 53.1 mg/L as ThOD_NH3) (average of 2 replicates). The test concentration of Sodium Benzoate used as a reference in the Procedure Control was 31.24 mg/L (equivalent to 52.17 mg/L as ThOD_NH3). In the toxicity control, containing both test item and reference, the test item was added to the test vessel at a level of 62.12 mg/L (equivalent to 53.42 mg/L as ThOD_NH3), the reference item was added at a level of 30.57 mg/L of sodium benzoate (equivalent to 51.05 mg/L as ThOD_NH3), The concentration expressed as the sum of ThOD_NH3 was 104.47 mg/L.

Based on the percentage degradation expressed as average, the percentage biodegradation of the test item after 28 days averaged 5.3% (2 replicates).

In the Abiotic sterile control test vessel without adddition of test inoculum and 3,5-Dichlorophenol 50 mg/L, the test item was added to the test vessel at a level of 60.72 mg/L of sodium benzoate (equivalent to 52.22 mg/L as ThOD_NH3). 

Based on the percentage bgiodegradation expressed as average, the percentage biodegradation of the test item after 28 days averaged 8.6% (2 replicates). The percentage degradation of the test item did not meet the pass level of 60% at the end of the test. 

Biodegradation of the reference substance (Sodium Benzoate) attained 64.2% after Day 5, 95.3 after Day 14 and 93.6% after Day 28.

In the toxicity control test mixture, 46.9% degradation ocurred within 14 days and the value exceeded 25% based on the sum of ThOD_NH3 which indicated that the test item can be assumed to be not inhibitory under the conditions of this test. 

Biodegradation of the abiotic sterile control attained 14.1 % after Day 28. 

Based on the results, the test item Methyl iodouracil is not 'readily biodegradable' under the described test conditions. 

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12th July 2018 to 10th August 2018

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))

Qualifier:

according to guideline

Guideline:

other: MEP, P.R. China, the Guidelines for the Testing of Chemicals, Degradation and Accumulation (2nd edition), No. 302C 'Inherent Biodegradability Modified MITI Test (II) (2013.9)

Qualifier:

according to guideline

Guideline:

other: European Commission Dir. 91/414 SANCO/3029/99 rev.4 1107/00 Guidance for generating and reporting methods of analysis in support of pre-registration data requirements of Annex II (part A, section 4)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge is collected from at least 10 sites, including Shenyang North, Shenshuiwan and Shenyang Xiannvhe Sewage Treatment Plants,
Weigong Channel, Maguan Bridge, Xinkai River, Ningguan Bridge, Hunhe River, Beiling Park and Nanhu Park on 7th June 2018.

- Preparation of inoculum for exposure:
- Pretreatment: Samples of sludge, surface water, soil etc. were collected respectively and 3L were mixed by stirring in a single container

After floating matter was removed, the sludge was allowed to stand and the supernatant was filtered through a fine sieve. 9L was drawn to fill 2 activated sludge vessels and the liquid aerated overnight.
30mins after stopping aeration. one third of the supernatant was discarded and an equal volume of 0.1% synthetic sewage (1% glucose, peptones and monopotassium phosphate) was added to the settled material and aerated again for 23.5 hours.
This procedure was repeated daily for 36 days.
After 36 days, 800ml of settled sludge was withdrawn and centrifuged for 5mins at 1500rpm. The supernatant was discarded and sludge was washed with mineral medium. After re-centrifuging the washed sludge again, the concentrated sludge was suspended in mineral medium. 10ml of the suspended sludge with 5 replicates was weighed and dried at 105oC for 1.5 hours and reweighed to calculate sludge concentration. The determined concentration of suspended sludge was 7706 mg/L, from this result the added amount of sludge was calculated.

Duration of test (contact time):

28 d

Initial conc.:

31.7 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
Stock Solution A: 0.85g of potassium acid phosphate, 2.175g of dipotassium hydrogen, 4.46g of dibasic sodium phosphate dodecahydrate and 0.17g ammonium chloride dissolved in deionised water and made up to 100ml
Stock Solution B: 2.25g magnesim sulfate heptahydrate added to deionised water and made up to 100ml
Stock Solution C: 2.75g calcium chloride or 3.64g calcium chloride dihydrate added to deionised water and made up to 100ml
To prepare 1L of mineral medium, 3ml of each of Stock Solutions A, B, C and D was added to deionised water and made up to 1L.

- Test temperature: 25 to 25.9 oC
- concentration of microbial inoculum: 100mg/L as Suspended Solids
Light: The test was carried out in darkness

TEST SYSTEM
- Culturing apparatus: 1L flasks
- Number of culture flasks/concentration: 3
- Measuring equipment: Automated Respirator CES UK Ltd

SAMPLING
- Sampling frequency: 24 hr intervals for 28 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: Test vessels containing inoculated mineral medium only were prepared in duplicate.
- Abiotic sterile control: 0.0314g of the test item was weighed into the test flask and 1000ml of deionised water added. The concentration of the test item was 31.4 mg/L. No inoculums were added to the test vessel. One replicate was sufficient.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (test mat. analysis)

Value:

3.2

Sampling time:

28 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

22.4

Sampling time:

28 d

Results with reference substance:

ThOD (NH3) 1.67 mg/O2/mg

Validity criteria fulfilled:

yes

Interpretation of results:

not inherently biodegradable

Conclusions:

Based on the grading criteria in the Guidelines for the Hazard Evaluation of New Chemicals substances State Environmental Protection Agency of PRC (HJ/T154-2004), the test item Methyl iodouracil did not meet the criteria for 'inherent and primary biodegradability' under the described conditions.

Executive summary:

This test assessed the inherent biodegradability of Methyl iodouracil on micro-organisms in an aerobic aqueous medium by measuring the Biochemical Oxygen Demand (BOD) and the residual amount of test item at the end of the test.

The percentage Sodium Benzoate reached 80.5% after the 7th day and 97.5% after 14 days. According to the criteria of MEP PR China Guidelines for the Testing of Chemicals, the test was considered valid. 

The concentration of test item in test suspension vessels averaged 31.7 mg/L (triplicate), the inoculum concentration was 100 mg/L as suspended solid. The amount of test item in the test medium was determined by HPLC at the end of the test.

The average residual amount of test item in inoculated medium at the end of the test was 25.4mg/L. The residual amount of test item in the abiotic control at the end of the test was 26.0mg/L

Based on the calculation for BOD, the percentage biodegradation after 28 days averaged 22.4% (triplicate). The percentage biodegradation of Methyl iodouracil exceeded the pass level of 20% after 28 days. 

However, based on the results from HPLC analysis, the primary percentage biodegradation in TS test vessels after 28 days incubation averaged 3.2% (triplicate), less than 20%.

The results from BOD and residual amount are conflicting. Under investigation, ther are no obvious reasons for differences between oxygen uptake values between TS and IC. After oxygen uptake values are divided by the THOD_NH3 of test item (0.86 mgO/mg TS) the differences were magnified and the results were not accurate. 

Therefore, the calculated biodegradability was seemingly higher compared with the value of the residual amount. The biodegradability (3.2%) from the residual amount analysis should be used as the final biodegradability rate in this study. 

Based on the grading criteria in the Guidelines for the Hazard Evaluation of New Chemicals substances State Environmental Protection Agency of PRC (HJ/T154-2004), the test item Methyl iodouracil did not meet the criteria for 'inherent and primary biodegradability' under the described conditions.

Description of key information

Ready biodegradability

The ready biodegradability test of Methyl iodouracil was conducted with unacclimatised sewage micro-organisms by measuring oxygen consumption over the 28 day test period. The test item was added directly to test vessels at a level of 61.77 mg/L (equivalent to 53.1 mg/L as ThOD_NH3) (average of 2 replicates). Based on the percentage degradation expressed as average, the percentage biodegradation of the test item after 28 days averaged 5.3% (2 replicates).

Based on the percentage bgiodegradation expressed as average, the percentage biodegradation of the test item after 28 days averaged 8.6% (2 replicates). The percentage degradation of the test item did not meet the pass level of 60% at the end of the test. 

Based on the results, the test item Methyl iodouracil is not 'readily biodegradable' under the described test conditions. 

 

Inherent biodegradability

This test assessed the inherent biodegradability of Methyl iodouracil on micro-organisms in an aerobic aqueous medium by measuring the Biochemical Oxygen Demand (BOD) and the residual amount of test item at the end of the test. The concentration of test item in test suspension vessels averaged 31.7 mg/L (triplicate), the inoculum concentration was 100 mg/L as suspended solid. The amount of test item in the test medium was determined by HPLC at the end of the test.

The average residual amount of test item in inoculated medium at the end of the test was 25.4mg/L. Based on the calculation for BOD, the percentage biodegradation after 28 days averaged 22.4% (triplicate). The percentage biodegradation of Methyl iodouracil exceeded the pass level of 20% after 28 days. 

However, based on the results from HPLC analysis, the primary percentage biodegradation in TS test vessels after 28 days incubation averaged 3.2% (triplicate), less than 20%.

The results from BOD and residual amount are conflicting. Under investigation, ther are no obvious reasons for differences between oxygen uptake values between TS and IC. After oxygen uptake values are divided by the THOD_NH3 of test item (0.86 mgO/mg TS) the differences were magnified and the results were not accurate. 

Therefore, the calculated biodegradability was seemingly higher compared with the value of the residual amount. The biodegradability (3.2%) from the residual amount analysis should be used as the final biodegradability rate in this study. 

Based on the grading criteria in the Guidelines for the Hazard Evaluation of New Chemicals substances State Environmental Protection Agency of PRC (HJ/T154-2004), the test item Methyl iodouracil did not meet the criteria for 'inherent and primary biodegradability' under the described conditions.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater