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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
Study period:
Experimental Phase: 26 November 2017 to 09 December 2017. Report Issue: 23 Jan 2019
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
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
The concentration and stability of the test item in the test preparations were verified by chemical analysis of the fresh media at 0 and 72 hours and of the old media at 24 and 96 hours.
Vehicle:
no
Details on test solutions:
A nominal amount of test item (2200 mg) was dispersed in 22 litres of test water with the aid of propeller stirring at approximately 1500 rpm for 24 hours. After 24 hours the stirring was stopped and any undissolved test item was removed by filtration through a 0.2 μm filter to give a 100% v/v saturated solution. A dilution was made from the 100% v/v saturated solution to give the required test concentration of 93% v/v saturated solution.

The test preparation was mixed with a flat bladed mixer for 1 minute to ensure adequate mixing and homogeneity.
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
TEST ORGANISM
- Common name: rainbow trout (Oncorhynchus mykiss).
- Source: Brow Well Fisheries Limited, Hebden, near Skipton, Yorkshire, UK.
- Length at study initiation (length definition, mean, range and SD): Mean standard length of 5.1 cm (SD = 0.3)
- Weight at study initiation (mean and range, SD): Mean weight of 1.09 g (SD = 0.26)

ACCLIMATION
- Acclimation period: 7 days
- Acclimation conditions (same as test or not): Same as test.
- Type and amount of food during acclimation: The fish were fed commercial trout pellets.

FEEDING DURING TEST
- Frequency: The fish were not fed during exposure to test substance and for 24 hours prior to the start of exposure.
Test type:
semi-static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
96 h
Hardness:
140 mg/L as CaCO3
Test temperature:
14 °C to 15 °C
pH:
7.7 at 0 hours (fresh media). 7.3 to 7.4 at 96 hours (old media).
Dissolved oxygen:
9.1 to 10 mg O2/L.
Conductivity:
μS/cm at 20°C (typical for water source)
Nominal and measured concentrations:
The test substance was dosed at a single nominal concentration of 93% v/v saturated solution.
Details on test conditions:
TEST SYSTEM
- Test vessel: 25 to 30 litre glass vessels
- Type (delete if not applicable): Covered to prevent evaporation
- Material, size, headspace, fill volume: 20 litres at 0, 24 and 72 hours and 18 litres at 48 hours
- Aeration: No
- Renewal rate of test solution (frequency/flow rate): A semi-static test regime was employed in the test involving a daily renewal of the test preparations to prevent the build-up of nitrogenous waste products.
- No. of organisms per vessel: 7 fish per vessel
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: Based on the mean weight value the loading rate was 0.38 g bodyweight/litre for the periods of 0 to 48 hours and 72 to 96 hours and 0.42 g bodyweight/litre for the period of 48 to 72 hours. The difference in loading rate throughout the test was due to a slightly reduced volume being used at 48 hours.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Laboratory tap water was 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 140 mg/L as CaCO3. After dechlorination and softening the water was passed through a series of computer controlled plate heat exchangers to achieve the required temperature.

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: photoperiod of 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition


EXAMINATIONS
Any mortalities and sub-lethal effects of exposure were recorded at 1, 3, 6, 24, 48, 72 and 96 hours 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.:
> 93 other: % v/v saturated solution
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Key result
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
93 other: % v/v saturated solution
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
There were no mortalities during the test.

There were no sub-lethal effects of exposure observed in the seven fish exposed to a test concentration of 93% v/v saturated solution for a period of 96 hours.

Validation Criteria
The test was considered to be valid given that none of the control fish died or showed signs of stress during the test and that the oxygen concentration at the end of the test was ≥ 60% of the Air Saturation value (ASV) in the control and test vessels

Chemical analysis of the freshly prepared test preparations at 0 and 72 hours and of the old or expired test preparations at 24 and 96 hours showed measured test concentrations of less than the limit of quantification (LOQ) of the analytical method employed were obtained which was determined to be 0.035 mg/L. This does not infer that no test item was in solution, just that any dissolved test item was at a concentration of less than the LOQ.

Validity criteria fulfilled:
yes
Conclusions:
Exposure of rainbow trout (Oncorhynchus mykiss) to the test substance gave LC50 values based on the nominal test concentration of greater than 93% v/v saturated solution. The No Observed Effect Concentration was 93% v/v saturated solution.
Executive summary:

Introduction

The study was performed to assess the acute toxicity of the test substance to rainbow trout (Oncorhynchus mykiss). The method followed was designed to be compatible with the OECD Guideline for Testing of Chemicals (1992) No 203, "Fish, Acute Toxicity Test".

 

Method

A preliminary media preparation trial indicated that saturated solution method of preparation was most appropriate for this test item.

 

In accordance with the recommendations of REACH, the test was conducted according to the threshold approach recommended by ECHA. Using this approach the lowest EC50 value from either the Algal Growth Inhibition study or Acute Toxicity to Daphnia magna study is set as the threshold concentration and a “Limit test” is conducted at this threshold concentration. If no mortalities are observed this indicates that fish are not the most sensitive species and that the LC50 is greater than the threshold concentration. The EC50 value obtained from the Algal Growth Inhibition study was the lowest of these two EC50 values and hence the test was conducted at a single concentration of 93% v/v saturated solution.

 

Seven fish were exposed to an aqueous solution of the test substance, at a single concentration of 93% v/v saturated solution for a period of 96 hours at a temperature of 14 ºC to 15 °C under semi-static test conditions. The test item solution was prepared by stirring an excess (100 mg/L) of test item in test water using a propeller stirrer at approximately 1500 rpm for 24 hours.

 

After the stirring period any undissolved test substance was removed by filtration through a 0.2 μm to produce a saturated solution of the test substance. A dilution was then performed in test water to give the test concentration of 93% v/v saturated solution. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 1, 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours.

 

Result

Chemical analysis of the freshly prepared test preparations at 0 and 72 hours and of the old or expired test preparations at 24 and 96 hours showed measured test concentrations of less than the limit of quantification (LOQ) of the analytical method employed were obtained which was determined to be 0.035 mg/L. This does not infer that no test item was in solution, just that any dissolved test item was at a concentration of less than the LOQ.

 

Conclusion

Exposure of rainbow trout (Oncorhynchus mykiss) to the test substance gave LC50 values based on the nominal test concentration of greater than 93% v/v saturated solution. The No Observed Effect Concentration was 93% v/v saturated solution.

Description of key information

Key value for chemical safety assessment

LC50 for freshwater fish:
0.035 mg/L

Additional information