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

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June 2001 to 18 April 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 210 (Fish, Early-Life Stage Toxicity Test)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples were taken on days 0, 9, 15, 22, 29, 36, 43, 50, 57, 65, 71, 78, 85 and 91.
Analysis was performed in general on the sampling day.

Vehicle:

no

Details on test solutions:

A constant flow test item delivery system equipped with membrane pumps was used for test item stock solution and dilution water delivery. The nominal flow rate of test solution into each test vessel was 50 mL/min. Since two replicates for each treatment level and the control were used, each mixing cell (which also splits the test solution for delivery into the two replicate test vessels) received 100 mL test solution per minute. The stock solutions with nominal concentration of 200 mg test item/L were prepared by diluting nominal 1.00 g test item in 5 L fish medium. Stock solutions with 40 mg test item/L were prepared by diluting 1 L of the 200 mg test item/L stock solution to 5 L fish medium.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

Fertilized rainbow trout eggs were obtained from Forellenhof Ma'ndli, 4410 Liestal, Switzerland. The eggs were introduced into the test solutions within 5 to 5.5. hours after fertilization.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

91 d

Hardness:

Hardness: from 156 to 192 mg/L
alkalinity: from 26 to 32 mg/L

Test temperature:

8.9 - 11.5°C

pH:

6.86 - 7.95

Dissolved oxygen:

6.42 - 11.01 mg/L (60 to 102 % saturation)

Salinity:

Not applicable

Conductivity:

Not available

Nominal and measured concentrations:

Nominal: 0.1, 0.3, 1.0, 3.0, 9.0, and 27.0 mg a.s./L
Measured: 0.0994, 0.307, 0.977, 3.14, 9.02 and 26.9 mg a.s./ L

Details on test conditions:

To start the exposure (day 0), the egg incubation cups were suspended in the respective exposure aquaria (four cup per replicate vessel). Four additional egg cups for determination of the viability were suspended in the control replicates. After completion of hatch (> 95 % of the embryos hatched, day 0 post-hatch), 30 randomly selected larvae were transferred into the larvae chambers. On day 14 post-hatch (day 45), the larvae were released from the larval chambers into the test vessels. Starting on day 42, the fry were fed live brine shrimp nauplii (Artemia salina) in general at least twice daily. At each feeding, fry were fed an excess of live brine shrimp ad libitum such that all fry were afforded equal access to food.

The aquaria were impartially positioned in a water bath containing circulating water designed to maintain the test solution temperatures at 10 ± 1 °C. The test vessels had following dimensions: length: 29.5 cm, width: 23.5 cm and were fabricated out of stainless steel. The water depth was approximately 16 cm resulting in a volume of approximately 10 litres test solution. The eggs and fry were kept in darkness until day 37, the day, all viable embryos were hatched. On day 37, a 16 hour light: 8 hour dark cycle was provided with a 30 minute transition period. The light intensity on day 37 was dimmed and gradually increased until day 39. From day 39 to day 91, the end of the exposure, the light intensity ranged from 400 to 580 lux during the light phases throughout the study. Light intensity measurements were performed at the test solutions surface during the light period.
Biomass load did not exceed 3.62 g/L or 0.503 g/L per 24 hours in any replicate test vessel.

Key result

Duration:

31 d

Dose descriptor:

NOEC

Effect conc.:

9.02 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: time to hatch and time to swim-up

Details on results:

Whereas the early-life-stages of rainbow trout were not affected by the test material at concentrations up to and including 9.02 mg a.s./L, significant effects occurred at the highest tested concentration of 26.9 mg a.s./L based on premature hatch and swim-up; therefore, the LOEC was set at 26.9 mg a.s./L.
The other considered parameters which included hatching rate, post-hatch survival, larval survival, larval development, morphological and behavioral abnormalities, all were inconspicuous in the treated groups as compared to the untreated control.

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

Table 1: Validity criteria for OECD 210 (2013)

Criterion from the guideline	Outcome	Validity criterion fulfilled
The dissolved oxygen concentration should be >60% of the air saturation value throughout the test.	60 to 102 % of the air-saturation value	Yes
The water temperature should not differ by more than ± 1.5 °C between test chambers or between successive days at any time during the test, and should be within the temperature ranges specified for the test species (Annex 2).	From 8.9°C to 11.5°C	Yes
The analytical measure of the test concentrations is compulsory.	Analytical measures performed	Yes
Overall survival of fertilised eggs and post-hatch success in the controls and, where relevant, in the solvent controls should be greater than or equal to the limits defined in Annex 2.	control hatching success recommended >75%: 91% control post-hatching recommended >75%: 98%	Yes       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 overall NOEC (31-day) for the early-life stages of O. mykiss was 9.02 mg a.s./L.

Description of key information

The overall NOEC for the early life stages of rainbow trout (Oncorhynchus mykiss) is 9.02 mg a.s./L.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

NOEC

Effect concentration:

9.02 mg/L

Additional information

Three GLP-studies are available for chronic toxicity in fish, therefore, the study dated 2002 was retained as key study. In this study, the long-term effects of the substance towards fish were examined in a 31-day early-life stage toxicity test with rainbow trout (Oncorhynchus mykiss) under flow-through conditions (2002). The study was carried out according to GLP and OECD 210. Fish were exposed to mean measured concentrations of 1.2, 2.3, 4.9, 9.8 and 19 mg a.s./L, alongside with a control and a solvent control. Whereas the early-life-stages of rainbow trout were not affected by the test material at concentrations up to and including 9.02 mg a.s./L, significant effects occurred at the highest tested concentration of 26.9 mg a.s./L based on premature hatch and swim-up. Based on mean measured concentrations of the test substance a NOEC (31d) of 9.02 mg a.s./L was determined.

 The remaining two studies were conducted according to US EPA guidelines, under GLP conditions with standard species (Oncorhynchus mykiss and Pimephales promelas). Both were considered suitable for supporting purpose.

 In the first supporting study (1992), the long-term effects of test material to rainbow trout was determined in a 98-d flow-through test according to U.S. EPA OPP 72-4 guideline. The NOEC for early-life stages was initially set at 9.8 mg a.s./L. Following a statistical re-evaluation of the data , the NOEC finally was corrected to 1.2 mg a.s./L, based on the  most sensitive endpoints referring to growth.

The second supporting study (2012) in fact was conducted according to the OPPTS Guideline 890.1350 (2009) to evaluate the test materials potential for endocrine activity. Therefore, mature fathead minnows (Pimephales promelas) were exposed under flow through conditions to the test material for 21 days. Since no obvious findings were noticed up to and at the híghest tested concentration of 9.02 mg a.s./L, the NOEC was ≥ 9.02 mg a.s./L.