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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:
weight of evidence
Study period:
From December 02, 1999 to December 14, 1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.1 (Acute Toxicity for Fish)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
The concentration and stability of the test substance 70 %, in the test solutions were verified by chemical analysis at 0 h (fresh media), 24 h (old media) and 96 h (old media).
Vehicle:
no
Details on test solutions:
For the purpose of the definitive study the test substance was prepared by direct solution in water. 4.00 g of the test substance 70 % was dissolved in dechlorinated tap water and the volume adjusted to 1 L to give a 4.00 g/L stock solution. An aliquot (500 mL) of this stock solution was dispersed in dechlorinated tap water and the volume adjusted to 20 L to give the 100 mg/L test concentration.
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
The test was carried out using juvenile rainbow trout (Oncorhynchus mykiss). Fish were obtained from Brow Well Fisheries Ltd., Hebden, Yorkshire, UK and maintained in-house since 24 November 1999. Fish were maintained in a glass fibre tank with a "single pass" water renewal system. Fish were acclimatised to test conditions from 8 December 1999 to 20 December 1999. The lighting cycle was controlled to give a 16 h light and 8 h darkness cycle with 20 min. dawn and dusk transition periods.

The water temperature was controlled at l4 °C with a dissolved oxygen content of greater than or equal to 9.2 mg 02/L. These parameters were recorded daily. The stock fish were fed commercial trout pellets which was discontinued approximately 24 h prior to the start of the definitive study. There was zero mortality in the 7 days prior to the start of the test and the fish had a mean standard length of 4.1 cm (sd = 0.1) and a mean weight of 0.81 g (sd = 0.06) at the end of the definitive study. Based on the mean weight value this gave a loading rate of 0.42 g bodyweight/L.

The diet and diluent water are considered not to contain any contaminant that would affect the integrity and outcome of the study.
Test type:
semi-static
Water media type:
other: dechlorinated tap water
Limit test:
yes
Total exposure duration:
96 h
Hardness:
Laboratory tap water dechlorinated by passage through an activated carbon filter (Purite Series 500) and partly softened (Elga Nimbus 1248D Duplex Water Softener) giving water with a total hardness of approximately 100 mg/L as CaC03. After dechlorination and softening the water was then passed through a series of computer controlled plate heat exchangers to achieve the required temperature.
Test temperature:
14 °C
pH:
While there were no treatment related differences for oxygen concentration the pH of the 100 mg/L test concentration was observed to be 0.2 pH units lower than the control values at 0, 24, 48 and 72 h (fresh media) and 0.1 pH units lower than the control values at 24, 48, 72 and 96 h (old media). This decline in pH was considered not to affect the validity or integrity of the study given that no mortalities or adverse reactions to exposure were observed.
Dissolved oxygen:
mg O2/L: 9.2 - 10
Nominal and measured concentrations:
Range finding study: 10 and 100 mg/L
Definitive study: 100 mg/L
Details on test conditions:
Range-finding study:

In the range-finding study fish were exposed to a series of nominal test concentrations of 10 and l00 mg/L. The test substance was dissolved directly in water.
4.0 g of the test substance was dissolved in dechlorinated tap water and the volume adjusted to 1 L to give a 4.0 g/L stock solution. Aliquots (50 and 500 mL) of this stock solution were each separately dispersed in dechlorinated tap water and the volume adjusted to 20 L to give the 10 and 100 mg/L test concentrations respectively.
In the range-finding study 3 fish were added to each 20 L test and control vessel and maintained at l4 °C in a temperature controlled room with a photoperiod of 16 h light and 8 h darkness with 20 min dawn and dusk transition periods for a period of 96 h under static test conditions.
The control group was maintained under identical conditions but not exposed to the test substance. Each vessel was covered to reduce evaporation. After 24, 48, 72 and 96 h any mortalities or sub-lethal effects of exposure were determined by visual inspection of the test fish.

Definitive study:

Based on the results of the range-finding study a "Limit test" was conducted for the definitive study at a test concentration of 100 mg/L.
As in the range-finding study 20 L glass exposure vessels were used for each test concentration. However each vessel contained 19.5 L of test medium due to sampling of the fresh media for analysis. At the start of the study 10 fish were placed in each test vessel at random, in the prepared test solutions. The test vessels were then covered to reduce evaporation and maintained at 14 °C in a temperature controlled room with a photoperiod of 16 h light and 8 h darkness with 20 min. dawn and dusk transition periods for a period of 96 h. The test vessels were aerated via narrow bore glass tubes. The fish were not individually identified and received no food during exposure.
The control group was maintained under identical conditions but not exposed to the test substance.
A semi-static test regime was employed. Any mortalities and sub-lethal effects of exposure were recorded at 3, 6, 24, 48, 72 and 96 h after the start of exposure. The criteria of death were taken to be the absence of both respiratory movement and response to physical stimulation.
Reference substance (positive control):
no
Key result
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Key result
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
Range-finding Study:
There were no sub-lethal effects of exposure during the range-finding study. The results showed no mortalities at the test concentrations of 10 and 100 mg/L.

Definitive Study:
There were no sub-lethal effects or mortalities of exposure observed in 20 fish exposed to a test concentration of 100 mg/L for a period of 96 h.

Chemical analysis:
Analysis of the test preparations at 0, 24 and 96 h showed the measured test concentrations to be near nominal and so it was considered justifiable to estimate the LC50 values in terms of the nominal test concentrations only.
Samples (Expressed as a % of the nominal concentration in two replicates):
0 h: 100; 99
24 h: 96; 96
96 h: 99; 100
The method has been considered to be sufficiently accurate for the purposes of this study. The test sample results have not been corrected for recovery. The limit of quantitation has been assessed down to 1.0 mg/L.

Stability:
The test samples have been shown to be sufficiently stable for the purposes of this study. The unsonicated vessel stability showed no evidence of insolubility or adherence to glass.

Validity criteria fulfilled:
yes
Conclusions:
Under the study conditions, the nominal 96 h LC50 in rainbow trout was 100 mg/L and the corresponding NOEC was 100 mg/L.
Executive summary:

A study was conducted to determine the acute toxicity of the test substance (Ammonium 2-mercaptopropionate) to rainbow trout (Oncorhynchus mykiss) according to OECD Guideline 203 and EU Method C.1. Following a preliminary range-finding study, fish were exposed, in two groups of ten, to an aqueous solution of the test substance at a single concentration of 100 mg/L for a period of 96 h under semi­static test conditions. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 h after the start of exposure and then daily throughout the study until termination. Analysis of the test solutions at 0, 24 and 96 h showed the measured test concentrations to be near nominal, therefore results were based on nominal concentrations. Under the study conditions, the nominal 96 h LC50 in rainbow trout was 100 mg/L and the corresponding NOEC was 100 mg/L (Sewell, 2000).

Description of key information

Key value for chemical safety assessment

LC50 for freshwater fish:
100 mg/L

Additional information

A study was conducted to determine the acute toxicity of the test substance (Ammonium 2-mercaptopropionate) to rainbow trout (Oncorhynchus mykiss) according to OECD Guideline 203 and EU Method C.1. Following a preliminary range-finding study, fish were exposed, in two groups of ten, to an aqueous solution of the test substance at a single concentration of 100 mg/L for a period of 96 h under semi­static test conditions. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 h after the start of exposure and then daily throughout the study until termination. Analysis of the test solutions at 0, 24 and 96 h showed the measured test concentrations to be near nominal, therefore results were based on nominal concentrations. Under the study conditions, the nominal 96 h LC50 in rainbow trout was 100 mg/L and the corresponding NOEC was 100 mg/L (Sewell, 2000).