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

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

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 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1010 (Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids)

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:

- Concentrations: 120 mg a.s./L
- Sampling method: All samples were collected at mid-depth and were placed in glass scintillation 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

Remarks:

dilution water

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- A 2-L primary stock solution was prepared at a nominal concentration of 120 mg a.s./L, the highest nominal concentration tested, by mixing a calculated amount of test substance into dilution water (UV sterilized well water). The primary stock was stirred to mix using a magnetic stir bar and stir plate for approximately 30 minutes followed by sonication for 50 minutes. The solution was brought up to volume with dilution water and inverted to mix. The primary stock solution appeared cloudy with no precipitate at the end of the mixing. Aliquots of the 120 mg a.s./L stock solution were proportionally diluted with UV sterilized well water to prepare 1-L batches of test solution at nominal concentrations of 7.5, 15, 30 and 60 mg a.s./L. The test solutions were mixed by inversion at least twenty times.
- At test termination, test solutions at 7.5, 15, 30 and 60 mg a.s./L appeared clear and colourless, while test solution at 120 mg a.s./L appeared clear and colourless with fine greyish precipitate on the bottom of the test chambers.

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain/clone: Cladoceran
- Source: Wildlife International, Ltd., Easton, Maryland
- Age of Daphnid neonates: <24 hours
- Feeding during test: Unfed
- Food type: Mixture of yeast, cereal grass media and trout chow (YCT), as well as a suspension of the freshwater green alga (Pseudokirchneriella subcapitata)
- Frequency: Daily. The adults were fed prior to test initiation, but neonates were not fed during the test.

ACCLIMATION
- Acclimation period: 21 days
- Type and amount of food: Mixture of yeast, cereal grass media and trout chow (YCT), as well as a suspension of the freshwater green alga (Pseudokirchneriella subcapitata)
- Feeding frequency: Daily
- Health during acclimation: The adults showed no signs of disease or stress and no ephippia were produced during the holding period.

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES: At test initiation, the juvenile daphnids were collected from the cultures and indiscriminately transferred one and two at a time to transfer chambers until each chamber contained five daphnids. Each group of daphnids then was transferred to an indiscriminately assigned test chamber. All transfers were made below the water surface using wide-bore pipettes.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test conditions

Hardness:

134 mg/L as CaCO3

Test temperature:

20 ± 1°C

pH:

7.7 to 8.6

Dissolved oxygen:

≥8.2 mg/L (≥91% of saturation)

Conductivity:

363 μS/cm

Nominal and measured concentrations:

Nominal: 0, 7.5, 15, 30, 60, 120 mg a.s./L
Measured: 0, 7.5, 14, 28, 56, 108 mg a.s./L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250-mL glass beakers containing 250 mL of test water
- Depth: 7.0 cm
- Aeration: Unaerated
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per vehicle control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Test facility 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.
- Alkalinity: 179 mg/L as CaCO3
- Hardness: 138 mg/L as CaCO3
- Specific conductance: 360 μS/cm
- pH: 8.1
- Chloride: 4.2 mg/L
- Total organic carbon at test initiation: <1 mg C/L

OTHER TEST CONDITIONS
- Photoperiod: 16 hours of light and 8 hours of darkness
- Light intensity: 371 lux

EFFECT PARAMETERS MEASURED: Observations were made periodically to determine the numbers of immobile organisms in each treatment group. The numbers of individuals exhibiting signs of toxicity or abnormal behaviour also were evaluated. Observations were made approximately 2.5, 24 and 48 hours after test initiation.

VEHICLE CONTROL PERFORMED: Yes

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 108 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: Immobility

Remarks on result:

other: The highest mean measured test concentration causing no immobility

Details on results:

Daphnids in the negative control group appeared normal throughout the test, with no immobility or sublethal effects observed. All daphnids in the 56 and 108 mg a.s./L treatment group also appeared normal throughout the test, with no immobility or overt signs of toxicity observed. Percent immobility at test termination in the 7.5, 14 and 28 mg a.s./L treatment groups was 5, 5 and 5% immobility, respectively, at test termination. All surviving daphnids in these groups appeared normal with no overt signs of toxicity observed. Since no immobile/mortality daphnids were observed in the 56 and 108 mg a.s./L treatment groups, the observed immobile daphnids in the 7.5, 14 and 28 mg a.s./L were considered to be incidental and not treatment related.

The highest mean measured test concentration causing no immobility at test end was 108 mg/L. The lowest mean measured test concentration causing 100% immobility at test end was greater than 108 mg/L. The EC50 values at 24 and 48 hours were estimated to be greater than the highest concentration tested.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

48 h EC50 (Daphnia magna): >108 mg a.s./L (highest mean measured test concentration)

Executive summary:

The acute toxicity of the test substance to unfed Daphnia magna was determined in an unaerated, static, 48-hour test. The test was conducted in accordance with the OECD Guideline for Testing of Chemicals, 202, and U.S. Environmental Protection Agency Series 850 – Ecological Effects Test Guidelines, OPPTS Number 850.1010. Treatments consisted of a dilution water control and mean measured test concentrations of 7.5, 14, 28, 56 and 108 mg a.s./L. Observations were made periodically to determine the numbers of immobile organisms in each treatment group. Immobility was defined as a lack of movement by the test organism except for minor activity of the appendages. The numbers of individuals exhibiting signs of toxicity or abnormal behaviour also were evaluated. Observations were made approximately 2.5, 24 and 48 hours after test initiation.

The 48-hour EC50 value was estimated to be greater than 108 mg a.s./L, the highest concentration tested. The highest mean measured test concentration causing no immobility at test end was 108 mg a.s./L. The lowest mean measured test concentration causing 100% immobility at test end was greater than 108 mg a.s./L.