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Ecotoxicological information

Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
Principles of method if other than guideline:
continuous flow conditions
GLP compliance:
not specified
Analytical monitoring:
yes
Vehicle:
yes
Details on test solutions:
stock solution: 10g test substance in 100 ml N,N-dimethylformamide (DMF)
The concentration has been confirmed by analytics.
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
Juveline rainbow trout were obtained from Mt. Lassen Trout Farm and maintained at SRI for at last two weeks prior testing.
Test type:
flow-through
Water media type:
freshwater
Limit test:
no
Total exposure duration:
13 d
Hardness:
28 mg/l CaCO3
Test temperature:
13°C
pH:
7.1 - 8.6
Dissolved oxygen:
mean 8.9 mg/l
Nominal and measured concentrations:
Nominal Concetrations tested (mg/l): 0; 0.9; 1.9; 3.8; 7.5; and 15
Only samples (n=6) from the highest concentrations were taken for chemical analysis, and the measured concentrations were below the level of detection, which probably contained less than 1 mg/l Thiofide.
Duration:
96 h
Dose descriptor:
LC0
Effect conc.:
< 1 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: highest nominal concentration, 15 mg/l, tested. However, all samples from highest concentration were below the detection level and probably contained less than 1 mg/l test substance.

No mortalities related to the toxicant occured in fish exposed to Thiofide at the highest nominal concentrations (15 mg/l) tested. However, all samples from highest concentration were below the detection level and probably contained less than 1 mg/l test substance. Because the actual stock concentraitons agreed very well with the nominal concentrations and syringe pumps and diluter were functioning properly, the test substance must have entered the test system at close to nominal levels. The water in test vessels were observed to be slightly cloudy in the highest concentration, and hence the test substance is suspected to be not fully soluble under the test temperature 13°C (water solubility at 25 °C: 0.27 -0.37 mg/L). The result can be interprated as LC0 higher than the water solubility of the MBTS at 13°C.

Conclusions:
No acute toxicity of MBTS was observed to Oncorhynchus mykiss up to its water solubility (<1mg/L) during 96 hours exposure in a flow-through system.
Executive summary:

No acute toxicity of MBTS was observed to Oncorhynchus mykiss up to its water solubility (<1mg/L) during 96 hours exposure in a flow-through system according to OECD Guideline 203 (Monsanto, 1981).

Description of key information

No acute toxicity of MBTS was observed to Oncorhynchus mykiss up to its water solubility (<1mg/L) during 96 hours exposure in a flow-through system according to OECD Guideline 203 (Monsanto, 1981).

Key value for chemical safety assessment

Additional information

Further supporting information from studies without analytical monitoring: - Monsanto (1979): 96h-LC0 >= 1000 mg/L to Pimephales promelas with the observation of precipitation in the test chamber - MITI Book (1992): 48h-LC50 = 19 mg/L to Oryzias latipes The effect concentrations are reported based on nominal concentrations and much higher than the water solubility of MBTS; and hence the observed effect is due to both dissolved and undissolved substance.