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

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01 Jun to 22 Jun, 1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 72-4 (Fish Early Life-Stage and Aquatic Invertebrate Life-Cycle Studies)

Version / remarks:

U. S. EPA-FIFRA, 40 CFR, Section 158.145 Guideline 72-4

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Analysis of the test water samples for the test material on days 0, 3, 5, 7, 10, 12, 14, 17, 19, and 21.
40 mL of test aquaria water were taken from the parent solution for each new solution sample day. 10 mL aliquots were taken from each replicate from the control, level 1, and 5 for a total of 40 mL, on alternate sampling days (3, 7, 12, 17 and 21), these days are referred to as old solution.

Vehicle:

yes

Remarks:

dimethylformamide

Details on test solutions:

A test material technical stock in DMF was prepared on June 1, 1990 for the preparation of the definitive test concentrations on each renewal day.
A working standard of the test material Technical was prepared on June 1, 1990 at a concentration of 75 mg/mL in DMF. The solution was stored in the refrigerator, and used to prepare test concentrations at each renewal. Test concentrations were prepared individually in 2 L volumetric flasks (Days 0, 3, 5, 7, 10, 12, 14, 17, 19 and 21) by diluting an appropriate volume of the test material working standard with dilution water. Solvent control solutions were prepared at a ratio of 0.2 mL of DMF to 2 L of dilution water. This represents the highest solvent concentration used in the test material concentrations.

Test organisms (species):

Daphnia magna

Details on test organisms:

Test specimens of Daphnia magna were obtained from an in-house daphnid culture which has been maintained by ABC since 1977. The primary culture was obtained from the Columbia National Fisheries Research Laboratory (CNFRL), Columbia, Missouri, in 1977.
During the holding period, the daphnids were fed a suspension of algae (Selenastrum capricornutum) supplemented with a trout chow and yeast suspension. Only first-instar daphnids (<24 hours old) were selected for testing.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

140-164 mg/L as CaC03

Test temperature:

20 (±2)°C

pH:

7.7-8.3

Dissolved oxygen:

5.8 to 9.1 mg/L (68 - 102% saturation)

Salinity:

Not applicable

Conductivity:

310-590 umhos/cm

Nominal and measured concentrations:

Nominal: 0.49, 0.94, 1.9, 3.8, and 7.5 mg/L
Mean Measured: 0.46, 0.86, 1.8, 3.6 and 7.3 mg/L

Details on test conditions:

The study was conducted as a static renewal in 1 L glass jars (16.5 cm height X 8.8 cm diameter) containing 400 mL of solution (6.6 cm depth). 4 replicate jars were used for the control, solvent control and each treatment concentration. The dilution water used in this study was a hard blended water. The specific water hardness was obtained by blending ABC well water with soft blended water (a combination of ABC well and reverse osmosis water). On study initiation, water hardness was at 140 mg/L
All test chambers were immersed in a thermostatically heated water bath adjusted to maintain the test concentrations at 20 (±2)°C. Lighting for the test system was provided by cool white fluorescent bulbs. This system provided a 16-hour light photoperiod with 30 minute dawn and dusk transition periods. Light intensity ranged from 51-53 footcandles at the water surface during the conduct of the study.

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

1.8 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth

Details on results:

The NOEC was based on the effects noticed for the daphnid length.
In fact, the length was statistically significantly affected when compared to the controls at the two highest measured test concentrations of 3.6 and 7.3 mg/L (control and solvent control: 4.5 ± 0.10 mm versus 4.3 ± 0.08 and 3.6 ± 0.15 mm at 3.6 and 7.3 mg/L test item, respectively).

Statistical analysis of survival for Daphnia magna after 21 days of exposure revealed a significant difference between the controls and the highest measured test concentration of 7.3 mg/L (control: 100 ± 0.0%, solvent control: 96 ± 8.3% versus 83 ± 13.6% at 7.3 mg/L of test item).

Reproduction days were statistically significantly affected at the highest measured test concentration of 7.3 mg/L, as compared to controls (control and solvent control: mean young/adult reproduction days of 15.7 ± 0.17 and 15.1 ± 0.75, respectively, versus 7.7 ± 0.65 at 7.3 mg/L of test item).

Statistical analysis of time to first brood for Daphnia magna after 21 days of exposure revealed no significant difference between treated groups and controls (Time to first brood: 7 days in all groups).

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 21-day NOEC for Daphnia magna was 1.8 mg/L under semi-static conditions, based on effects on the growth.

Description of key information

From the chronic toxicity study of the test substance on Cloeon dipterum the 21-day EC10 for aquatic invertebrates was 0.056 µg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.056 µg/L

Additional information

A GLP-study dated 1990 is available for long-term toxicity in aquatic invertebrate, which is considered suitable as key study. In this study, the long-term effects of the substance towards Daphnia magna were examined in a 21-day toxicity test under semi-static conditions. The study was carried out according to GLP and guideline EPA No. 72-4. Daphnia were exposed to mean measured concentrations of 0.46, 0.86, 1.8, 3.6 and 7.3 mg a.s./L, alongside with a control and a solvent control. Whereas the daphnia were not affected by the test material at concentrations up to and including 1.8 mg a.s./L, significant effects occurred at the two highest tested concentration of 3.6 and 7.3 mg a.s./L based on length. Based on mean measured concentrations of the test substance a NOEC (21d) of 1.8 mg a.s./L was determined.

A non-guideline study on chronic toxicity of the test substance on mayfliesis available. The EC10 (21 d) value was determined to be 0.000056 mg/L. This study was considered relevant and reliable for use in classification in accordance with RAC “Opinion proposing harmonised classification and labelling at EU level of imidacloprid” and will therefore be used for the PNEC derivation.