imidacloprid (ISO); 1-(6-chloropyridin-3-ylmethyl)-N-nitroimidazolidin-2-ylidenamine

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

05 Oct - 09 Oct 1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Version / remarks:

1984

Deviations:

yes

Remarks:

temperature slightly above the range of 10 to 14°C recommended by the current guideline version for the species used and only measured in control.

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Analytical determination of the active ingredient content was done for each aquarium at 0 and 24 hours as well as after 96 hours for those concentration groups, where no mortality occurred.
With respect to the sampling time point 96 h, a first sample for analysis was collected from the water under static conditions and a second one was collected after intensive tirring up of the water.

Vehicle:

no

Details on test solutions:

The test substance was directly applied to the test water without using solvents and was distributed as uniformly as possible.

The following amounts of test item (active ingredient a.i.) were added to the test water to obtain the nominal test concentrations as scheduled:
2.6 g in 50 L water (50 mg a.i./L)
4.7 g in 50 L water (89 mg a.i. /L)
8.3 g in 50 L water (158 mg a.i./L)
14.7 g in 50 L water (281 mg a.i./L)
26.2 g in 50 L water (500 mg a. i./L)

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

Rainbow Trout were obtained from Forellenzucht Linn, D-5940 Lennestadt, Germany. They were acclimatized in the test water and at the test temperature for at least 14 days. During this period they were fed a commercial fish diet (Tetramine, Tetra-Werke, D-4520 Melle, Germany). Feeding was stopped at least 48 hours before and during the test. The average bodyweight at the beginning of the test amounted to 1.3 ± 0.6 g, the average body length 5.3 ± 0.6 cm and the corpulence factor 0.8 ± 0.11 g/cm3

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

230 mg of CaCO /L

Test temperature:

15.4°C (14.8 - 16.4)

pH:

8.0 - 8.1

Dissolved oxygen:

9.9 - 10.8 mg/L (92 to 101 % saturation)

Salinity:

Not applicable

Conductivity:

Not available

Nominal and measured concentrations:

50, 89, 158, 281 and 500 mg a.s./L and an untreated control without additives

Details on test conditions:

TEST SYSTEM
- Test vessel: 50 L aquaria
- Aeration: yes
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: 0.26 g/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstitued water (salt solutions added to demineralized water)


OTHER TEST CONDITIONS
- Photoperiod: 16 hours light / 8 hours dark


EFFECT PARAMETERS MEASURED
The fish were examined daily for symptoms of intoxication and mortality

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.8
- Test concentrations: 5

Reference substance (positive control):

not required

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

211 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality (fish)

Remarks on result:

other: The concentration-activity-ratio was so narrow that 0 % and 100 % mortality were found in the neighboring concentrations at a factor of progression of 1.8.

Details on results:

Symptoms of intoxication occurred mainly at 158 mg a.i./L and higher concentrations and were noted as: swimming behavior slightly irregular (light symptom), apathy, lying on side/ back and staggering.

Sublethal observations / clinical signs:

Please refer to "overall remark/ attached background material" field for result tables.

Validity criteria for OECD 203 (2019)

Criterion from the guideline	Outcome	Validity criterion fulfilled
The mortality in the control(s) should not exceed 10% (or one fish if less than ten are used) at the end of the test	0%	Yes
The dissolved oxygen concentration must have been at least 60 per cent of the air saturation value throughout the test	92-101%	Yes
There must be evidence that the concentration of the substance being tested has been satisfactorily maintained, and preferably it should be at least 80% of the nominal concentration throughout the test. If the deviation from the nominal concentration is greater than 20 per cent, results should be based on the measuredconcentration.	The measured values were greater than 80 % of the nominal values in all aquaria over the whole test period	Yes

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Conclusions:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, the LC50 96 h for Oncorhynchus mykiss was 211 mg/L.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10 Sep - 14 Sep, 1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: Subdivision E, U.S. EPA Guideline No. 72-3

Deviations:

yes

Remarks:

aeration used to maintain acceptable dissolved oxygen concentrations, slight decrease in temperature, slight deviations in salinity and temperature of holding saltwater

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Concentrations of the test substance were measured in water samples collected at test initiation and termination from all test treatments and the controls. Samples (10 mL) were collected from midway in the water column using a pipet. All samples were analyzed on the day they were collected.

Vehicle:

yes

Remarks:

dimethylformamide (DMF)

Details on test solutions:

Each test solution was prepared by adding a measured quantity of test item directly into 1 liter of dilution water in an electric blender. To this mixture, 2.0 mL of dimethylformamide (DMF) was added and then the mixture was blended for one minute. The resulting solution was added to 19 L of dilution water in the test tank and stirred. A dilution water and solvent (DMF) control were maintained concurrently with the test solutions. The solvent control was prepared by adding 2.0 mL of DMF into 20 L of dilution water. The solvent concentration in the solvent control and all test solutions was 100 µL/L.

Test organisms (species):

Cyprinodon variegatus

Details on test organisms:

Young adult sheepshead minnow (Cyprinodon variegatus) were obtained from a commercial supplier (Cultured Aquatics, Northport, New York) and maintained in the laboratory in natural saltwater for approximately 2 months prior to test initiation. During the 7-day period immediately prior to test initiation, fish were maintained in saltwater with a salinity range of 21 to 24 part per thousand and a temperature of 22.9 to 26.8 °C. Fish were fed daily throughout the holding period with commercial flake feed from Ziegler Brothers, Inc., Gardners, PA. No diseases were observed and no disease treatments were administered during holding of the fish. During the 48-hour period immediately prior to initiation of the 96-hour exposure, salinity and water temperture ranges were 23 to 24 part per thousand and 22.9 to 26.4 °C, respectively. Sheepshead minnow were not fed and there were no mortalities during the 48-hour period immediately prior to start of the test. Sheepshead minnow used for this test ranged from 25 to 33 millimeters (mm) standard length (mean and standard deviation = 2 9 ± 2 mm) and from 0.47 to 1.35 grams (g) wet weight (mean and standard deviation = 0.77 ± 0.30 g)

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

not reported

Test temperature:

19.5 to 21.6°C

pH:

7.7 - 8.6

Dissolved oxygen:

4-105%

Salinity:

20 to 22 part per thousand

Conductivity:

not reported

Nominal and measured concentrations:

Nominal concentrations: control, solvent control, 26, 44, 72, 120 and 200 mg/L
Mean measured concentrations: control, solvent control, 22.4, 35.2, 58.2, 105 and 195 mg/L

Details on test conditions:

The test containers were glass tanks with capacity of 23.6 L, filled with 20 L of dilution water providing a water depth of 18 cm.

Reference substance (positive control):

not required

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

161 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

mortality (fish)

Details on results:

Mortality at 96 h ranged from 0% in the control and at test concentrations < 58.2 mg/L to 70% at 195 mg/L.

Sublethal observations / clinical signs:

Please refer to "overall remark/ attached background material" field for result tables.

Validity criteria fulfilled:

not specified

Conclusions:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, the LC50 96 h for Cyprinodon variegatus was 161 mg/L.

Description of key information

From short-term key studies, the 96-hour LC50 for fish exposed to the present test material was 211 mg a.s./L for O. mykiss in freshwater and 161 mg a.s./L for C. variegatus in saltwater.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

LC50

Effect concentration:

211 mg/L

Marine water fish

Marine water fish

Dose descriptor:

LC50

Effect concentration:

161 mg/L

Additional information

Five GLP-studies are available for short-term toxicity testing in fish and two of them were identified as key studies.

In the first key study (1988), the acute toxicity of test material to fish was investigated in a 96-hours static test with the rainbow trout (Oncorhynchus mykiss) according to guideline OECD 203. Ten fish per test concentration were exposed for 96 hours under static conditions to nominal concentrations of 50, 89, 158, 281 and 500 mg a.s./L, alongside with a control. The 96-hour LC₅₀ was determined to be 211 mg a.s./L. All calculations refer to nominal values. Based on this study, the LC₅₀ for rainbow trout exposed to test material in the freshwater water was 211 mg a.s./L.

In the second key study (1990), the acute toxicity of test material to fish was investigated in a 96-hours static test with the sheepshead minnow (Cyprinodon variegatus) according to guideline EPA No. 72-3. Ten fish per test concentration were exposed for 96 hours under static conditions to nominal concentrations of 26, 44, 72, 120 and 200 mg a.s./L, alongside with a control and a solvent control. The 96-hour LC₅₀ was determined to be 161 mg a.s./L, referring to mean measured values. Based on this study, the LC₅₀ for sheepshead minnow exposed to test material in the saltwater water was 161 mg a.s./L.

There are three additional studies available, conducted with Leuciscus idus (golden orfe), Oncorhynchus mykiss (rainbow trout) and Lepomis macrochirus (bluegill), respectively; the resulting LC₅₀ values ranged between 83 and 237 mg a.s./L. These studies were considered suitable for supporting purpose.

In the first supporting study (1987), the acute toxicity of test material to golden orfe was determined in a 96-h-static test according to EEC-guideline "EEC DIRECTIVE 79/831/WG, Annex V, Methods for Determination of Eco- toxicity, Method 5.1.1. Acute Toxicity for Fish".The 96-hour LC50 of the technical active ingredient was determined to be 237 mg a.s./L based on nominal concentrations.

In the second supporting study (1990), the acute toxicity of test material to rainbow trout was determined in a 96-h-static test according to U.S. EPA OPP 72-1 guideline. The 96-hour LC50 of the technical active ingredient was determined to be > 83 mg a.s./L which was the highest measured test concentration.

In the third supporting study (1990), the acute toxicity of test material to bluegill sunfish was determined in a 96-h-static test according to U.S. EPA OPP 72 -1 guideline. The 96-hour LC50 of the technical active ingredient was determined to be > 105 mg as/L which was the highest measured test concentration.