ethametsulfuron-methyl (ISO); methyl 2-[(4-ethoxy-6-methylamino-1,3,5-triazin-2-yl)carbamoylsulfamoyl]benzoate

Short-term toxicity to fish

Administrative data

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Report date:

2009

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1075 (Freshwater and Saltwater Fish Acute Toxicity Test)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 002

Cas Number:

97780-06-8

Test material form:

solid

Details on test material:

Purity: 99.2%

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Samples were collected from each test chamber at test initiation and termination to measure concentrations of the test substance. The samples were collected at mid-depth and placed in glass vials. Two sets of samples were collected at each interval. One set was processed immediately for analysis. The second set was stored refrigerated for possible future analysis.

Test solutions

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The test solution for each test chamber was prepared, individually, at a nominal concentration of 120 mg active substance/L. The solution was prepared by mixing calculated amounts of the test substance into 25 L of dilution water (well water). Test solutions were adjusted to 100% active substance based upon the reported test substance purity of 99.2%. Prior to test solutions preparation, 25-L of dilution water was measured into each test chamber, using a calibrated plastic vessel. The test substance was weighed into a tared beaker and rinsed directly into the 25-L dilution water in each treatment test chamber. The test substance and dilution water were mixed using a top-down electric mixer for approximately 21 hours. At the beginning of the mixing period, test solution at 120 mg a.s./L was gray and slightly opaque with white precipitate observed on the surface of the solution. A glass pasteur pipette was used to rinse the test substance adhering to the sides of the test chambers into the solutions. At the end of the mixing, all solutions appeared clear and colorless.
- Controls: The negative control was dilution water only
- Chemical name of vehicle: Dilution water

Test organisms

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Strain: Oncorhynchus mykiss
- Source: Thomas Fish Company, Anderson, California
- Age at dosing: Juvenile
- Length at end of the test (negative control fish): 4.3 to 5.1 cm
- Weight at end of the test (negative control fish): 0.76 to 1.6 grams

ACCLIMATION
- Acclimation period: 14 days
- Type and amount of food during acclimation: Fish were fed commercially-prepared diet, and were not fed for at least two days prior to the test or during the test.
- Health during acclimation: During the 2-week period prior to the test the fish showed no signs of disease or stress and no mortalities occurred during the 7 days prior to the test.

FEEDING DURING TEST
- Frequency: Unfed

Study design

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Test conditions

Hardness:

136 mg/L as CaCO3

Test temperature:

11.7 to 12.8°C

pH:

8.1 to 8.5

Dissolved oxygen:

≥7.8 mg/L (72% of saturation)

Conductivity:

396 μS/cm

Nominal and measured concentrations:

Nominal: 120 mg a.s./L
Mean measured: 126 mg a.s./L

Details on test conditions:

TEST SYSTEM
- Test vessel: 38-L stainless steel aquaria containing 25 L of test solution
- No. of organisms per vessel: 10 fish
- No. of vessels per concentration (replicates): 3
- Aeration: gentle aeration was initiated in each test chamber to ensure that dissolved oxygen concentrations remained above 60% saturation through test termination.
- Loading: 0.52 g fish/L (wet weight of fish per liter of test water)

TEST MEDIUM / WATER PARAMETERS
- Preparation of dilution water: The water used for culturing and testing was obtained from a well approximately 40 meters deep located on the test facility site. The well water was passed through a sand filter to remove particles greater than approximately 25 μm, and pumped into a 37800 L storage tank where the water was aerated with spray nozzles. Prior to use, the water was filtered to 0.45 μm and passed through an ultraviolet sterilizer to remove fine particles and microorganisms. The well water is characterized as moderately-hard water.
- Alkalinity: 180 mg CaCO3/L

OTHER TEST CONDITIONS
- Photoperiod: 16 hr photoperiod (218 lux at initiation) and 8 hr darkness which included 30-minute transition period of low light intensity was provided when lights went on and off to avoid sudden changes in lighting.

EFFECT PARAMETERS MEASURED: Observations were made periodically to determine the number of dead organisms in each treatment group. Lethality was defined as a lack of visible movement by the test organism. The numbers of individuals exhibiting signs of toxicity or abnormal behaviour also were evaluated. Observations were made approximately 2.5, 24, 48, 72 and 96 hours after test initiation.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 126 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

mortality (fish)

Details on results:

All trout in the negative control group and the 126 mg a.s./L test groups appeared normal throughout the test, with no mortality or sublethal effects observed.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

96-hour LC50 (Oncorhynchus mykiss): >126 mg a.s./L (mortality)

Executive summary:

The acute toxicity of the test substance to unfed juvenile rainbow trout (Oncorhynchus mykiss), a freshwater fish, was determined in a static, 96-hour limit test. The test was conducted in accordance with the OECD Guideline for Testing of Chemicals, 203, Fish Acute Toxicity Test and U.S. Environmental Protection Agency Series 850 –Ecological Effects Test Guidelines, OPPTS Number 850.1075, Fish Acute Toxicity Test, Freshwater and Marine. Treatments consisted of a dilution water control and a nominal test substance concentration of 120 mg active substance/L. The corresponding mean, measured concentration was 126 mg a.s./L. All trout in the negative control group and the 126 mg a.s./L test groups appeared normal throughout the test, with no mortality or sublethal effects observed. The 96-hour LC50 for rainbow trout, Oncorhynchus mykiss, based on the mean, measured concentration and mortality was greater than 126 mg a.s./L, the limit test concentration.