Methanethiol

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

from 06/07/99 to 03/05/00

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: 1a: GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2000

Report date:

2000

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Sodium methanethiolate

EC Number:

225-969-9

EC Name:

Sodium methanethiolate

Cas Number:

5188-07-8

IUPAC Name:

sodium methanethiolate

Details on test material:

- Name of test material: sodium methyl mercaptide at 32.9 % in water
- Lot/batch No.: SMM33 990103935
- Physical state: clear liquid at 40 °C
- Solubility: totally soluble at 20 °C

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
not relevant

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

no data

Test solutions

Vehicle:

yes

Details on test solutions:

A stock solution was prepared before the beginning of the test, by vigorously mixing 8 mg of the substance with 1 liter of dilution water for 24 hours. 

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna Straus
- Strain: Clone A (Clone 5)
- Age at study initiation: < 24h old
- Breeding colony maintained in the laboratory in an Elendt M7 medium , supplemented with algal based feed (Raphidocelis subcapitata).
- Organisms were selected by sieving.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test conditions

Hardness:

no data

Test temperature:

19±1°C

pH:

from 7.93 to 8.22

Dissolved oxygen:

from 9.0 to 9.6 mg/L

Nominal and measured concentrations:

Nominal concentrations: 0.6 - 1.0 - 1.7 - 2.9 and 5.0 mg/L
Measured concentrations: 0.83 - 1.32 - 2.46 - 4.38 and 7.47 mg/L
Geometric progression with a factor of 1.7. An untreated control was also included.

Details on test conditions:

TEST SYSTEM
- Test vessel: 120 mL test glassware was entirely filled with test solutions and stoppered with PTFE bungs and sealed with aluminium caps
- Type: closed
- No. of organisms per concentration: 20 daphnids per concentration
- 4 replicates , 5 individuals per replicate

OTHER TEST CONDITIONS
- Darkness

WATER PARAMETERS
- Ca+Mg ions = 2.5 mmol/l
- Ca/Mg = 4      
- Na/K = 10

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.32 - 2.46 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Effect concentrations 2

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

4.38 - 7.37 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

The appearance of the test solution was visually checked at the beginning and at the end of the test.  Solutions were found to be clear and colourless over the period of the test.  No precipitation was observed at the end of the test.

Results with reference substance (positive control):

Potassium dichromate: EC50-24h = 1.6 mg/L

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

see conclusions

Conclusions:

The study was performed in compliance with its quality criteria:
- Test daphnids in the control were not trapped at the surface of the water.
- Concentration of dissolved oxygen in the test vessel remained above 2 mg/L at the end of the test and pH did not vary by more than 1 unit.
- No more than 10 % of the daphnids immobilized in the control at the end of the test.
- Concentrations of the test substance were maintained within 80 % of the initial concentrations throughout the duration of the test.

Executive summary:

Acute toxicity to Daphnia magna has been investigated according to OECD Guideline 202 and EU Method C.2.

Daphnia magna were exposed for 48 hours to an aqueous solution of sodium methanethiolate at different nominal concentrations of 0.6 - 1.0 - 1.7 - 2.9 and 5.0 mg/L.

EC 50 - 48h determined was in the range of 1.32 - 2.46 mg/L and EC50 - 24h was in the range of 4.38 - 7.37 mg/L.