Methylthiouracil

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

30/01/2018 - 10/08/2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Methylthiouracil

EC Number:

200-252-3

EC Name:

Methylthiouracil

Cas Number:

56-04-2

Molecular formula:

C5H6N2OS

IUPAC Name:

methylthiouracil

Test material form:

solid: crystalline

Specific details on test material used for the study:

6.1.1 Test Item Information
(as provided by the Sponsor)

Batch manufactured and supplied by : Korde Chemicals Pvt Ltd.
W-13, TTC Pawane MIDC,
NaviMumbai 400705 INDIA

Test item : 6-METHYL-2-THIOURACIL

CAS No. : 56-04-2

Chemical name (IUPAC) : 6-METHYL-2-SULFANYLIDENE-1H-PYRIMIDIN-4-ONE

Physical appearance : White powder

Purity as per CoA : 98.46%

Batch No. : 151117

pH 0.1 % : 6.20

Manufactured date : 15 November 2017

Expiry date : 14 November 2019

Recommended storage condition : Ambient (+15 to +25°C)

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Vehicle:

not specified

Details on test solutions:

The medium used for the test was reconstituted water, as described in the OECD test guideline 202 (OECD, 2004). The medium was prepared as per the details given in Appendix 2.

All chemicals used in the study were of either analytical reagent (AR) or better grade reagent.

Chemical Batch No. Manufacturer
Magnesium sulphate. 7H2O H14A/1813/1707/31 S. D. fine-chem Limited
Mumbai-400030
India

E.D.T.A-disodium salt F10Z/1710/1705/31
Methyl orange indicator D16Z/1112/2402/74
Ammonium chloride D14A/2314/2103/31
Patton & Meders indicator F11Z/0311/1102/31
Ammonium hydroxide L11A/0711/2202/31
Calcium chloride, 2H2O D14A/1314/0804/31
Sodium hydroxide D16A/0415/2112/31
Hydroxyl ammonium chloride 1504/17101-1 Qualigens Fine Chemicals
Navi Mumbai
India
Potassium chloride QJ3P631025 Merck Specialities Private Limited, Mumbai
India
Sodium carbonate QC2Q620547
Erichrome Black T AL0A601067
Sodium chloride QL4Q642763
Phenolphthalein Indicator 0000245703 Himedia laboratories Pvt. Ltd.
Mumbai, India
Sodium bicarbonate 0000230345
Hydrochloric acid SHBG4416V Sigma Aldrich, 3050 Spruce street, St. Louis, USA

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

Daphnia magna was used as test system as it is a recommended species in the guideline.

6.1.2.1 Source
Ecotoxicology
Eurofins Advinus Limited
Bengaluru
India
6.1.2.2 Maintenance of Daphnia
Daphnia were maintained in the test medium. The test medium in which the daphnia were maintained was changed at least twice a week and they were fed with the unicellular green alga, Chlorella vulgaris.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Test conditions

Hardness:

not specified

Test temperature:

20.3-20.6

pH:

7.69-7.85

Dissolved oxygen:

7.0-7.9

Salinity:

not specified

Conductivity:

not specified

Nominal and measured concentrations:

0.3 (G2), 0.66 (G3), 1.45 (G4), 3.19 (G5), 7.02 (G6) and 15.44 (G7) mg/L

Reference substance (positive control):

yes

Results and discussion

Effect concentrations

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.738 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The EC50 value for 6-Methyl-2-Thiouracil at 48 hours was 1.738 mg/L based on nominal concentrations with fiducial limits at 95 % being 1.2918 and 2.3378 mg/L.

Executive summary:

The acute immobilization effect of the test item6-Methyl-2-Thiouracilwas studied onDaphnia magna.

 

In the definitive test, theDaphnia magnaof less than 24 hours old were exposed to concentrations of 0.3, 0.66, 1.45, 3.19, 7.02 and 15.44 mg/L of6-Methyl-2-Thiouracilalong with a negative and reference substance in reconstituted water at 20 ± 1^oC. The number of daphniaimmobilized was recorded at 24 and 48 hours post exposure.

 

There was no immobilization of daphnia in the negative control either at 24 or at 48 hours post-exposure. The immobilization of daphniawas 0, 0, 10, 35, 80 and 90% at 24 hours and 10, 15, 45, 60, 100 and 100 % at 48 hours post-exposure at the tested concentrations of 0.3, 0.66, 1.45, 3.19, 7.02 and 15.44 mg/L of6-Methyl-2-Thiouracil.There was 55 and 60% immobilization of daphnia in thereference substance (potassium dichromate), at 24 and 48-hour post exposure, respectively, indicating the sensitivity of the test procedure used.

 

The EC₅₀value for6-Methyl-2-Thiouracilat 24 hours was 4.203 mg/L based on nominal concentrations with fiducial limits at 95 % being 3.1736 and 5.5655 mg/L.

 

The EC₅₀value for6-Methyl-2-Thiouracilat 48 hours was 1.738 mg/L based on nominal concentrations with fiducial limits at 95 % being 1.2918 and 2.3378 mg/L.