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

Toxicity to terrestrial arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to non-target arthropods on inert substrate (NTA other than pollinators)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

31 May - 28 Jun, 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

ISO 11267 (Inhibition of Reproduction of Collembola by Soil Pollutants)

Version / remarks:

ISO/FDIS 11267 (1998)

Deviations:

yes

Remarks:

slight deviation of number of juvniles per control replicate

GLP compliance:

yes (incl. QA statement)

Remarks:

Niedersächsisches Umweltmlnlsterium; delivered on 07 July 1997

Application method:

mixed into soil

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

The test substance was applied to the artificial soil with an amount of deionised water to adjust an overall moisture content of about 50 % of its maximum water holding capacity.
The test substrate was mixed with a household mixer for at least three minutes. Afterwards soil amounts (ca. 30 g wet weight per replicate) were distributed to the single replicates. To insure easy migration of springtails the substrate in the test containers was not compressed.

Test organisms (species):

Folsomia candida

Animal group:

Collembola (soil-dwelling springtail)

Details on test organisms:

Juvenile springtails (10 - 12 days old) were used. They were obtained by transferring egg clusters from breeding containers to freshly prepared containers. After 48 h the egg clusters were removed and the hatched instars were fed. The springtails were sucked from the breeding containers using an exhauster. Before transfer to the test containers they were counted and checked for damage both to reduce control mortality and to avoid systematical trial errors. Springtails were set in by a randomized procedure.
Springtails were fed with 2 mg granulated dry yeast per replicate at the beginning of the test and after 14 days.

Study type:

laboratory study

Limit test:

no

Total exposure duration:

28 d

Test temperature:

20 ± 2 °C

pH (if soil or dung study):

5.50 - 5.59

Humidity:

An overall moisture content of about 50 % of its maximum water holding capacity.
Evaporated water was added to maintain the soil moisture which should not deviate by more than 2 % of the initial value.

Photoperiod and lighting:

Light / dark cycle of 16 / 8 h per day
400 - 800 Iux

Details on test conditions:

Artificial soil as test medium was used as described by the guideline. It consists of components as follows:
- 10 % peat, air dried and finely ground
- 20 % kaolin, kaolinite content > 30 %
- 69 % quartz sand, sand with > 50 % particles sized 50-200 µm
- 0.4 % calcium carbonate (CaCO3)

Glass beakers with a volume of 100 mL (0 = 4.3 cm) were used and covered with PARAFILM. Test containers were opened briefly twice per week to allow aeration.
10 organisms par replicate. 5 Replicates per control, 6 replicates per test substance.
The test substrate was poured into a petri dish and watered with dechlorinated tap water. After gentle stirring of the suspension with a spatula springtails drifted to the water surface. Black ink was added to the water to improve the contrast. Slides of the water surface were prepared using appropriate photographic equipment. Springtails were counted at the projected slide. Missing springtails were counted as dead due to rapid degradation.

Nominal and measured concentrations:

Nominal: 0.3, 0.6,1.25, 2.5, 5 and 10 mg/kg dry weight

Reference substance (positive control):

yes

Remarks:

500 g/L Parathion

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

1.25 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Details on results:

The mean mortality after 28 days in the control group was 8 %. The NOEC and LC50 for mortality were 0.3 and 2.7 mg/kg respectively.
The mean number of juveniles found in the untreated control was 123. The EC50 for reproduction was 3.4 mg/kg.

Results with reference substance (positive control):

After 28 days adult mortality and number of instars were determined. NOEC and EC50 were 0.05 and 0.15 (CI:0.12-0.19) respectively.

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

Table 1: Validity criteria according to the ones reported in the report

Criterion from the guideline to be satisfied in the controls	Outcome	Validity criterion fulfilled
Mortality over the 4 weeks of the test is ≤ 20%.	8%	Yes
The mean number of instars (with 10 collembolans introduced) should be ≥ 100 per replicate.	At least 76	No
The coefficient of variation calculated for the number of juveniles per replicate is ≤ 30%.	30%	Yes

The number of instars per replicate in control should be > 100. In this study in four replicates of the control > 100 instars were observed. Only 1 replicate showed with 76 instars a lower reproduction rate. Then mean number of instars in control was 123 instars per replicate. Therefore the study is assumed to be valid.

Validity criteria fulfilled:

yes

Remarks:

According to the report. 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 reproduction NOEC (28-day) for Folsomia candida was 1.25 mg a.s./ kg dw soil.

Description of key information

The NOEC was determined to be 1.25 mg test substance/kg soil d.w.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil dwelling arthropods:

1.25 mg/kg soil dw

Additional information

In the key study (1999), the chronic toxicity of test material technical to collembola (Folsomia candida) was investigated after 28-day exposure according to ISO/FDIS 11267(1998) guideline. The test item was incorporated into the soil. Ten female collembola per replicate were exposed to concentrations of 0.3, 0.6, 1.25, 2.5, 5 and 10 mg/kg dry weight soil, alongside with a control. The reproduction NOEC was determined to be 1.25 mg test substance/kg soil d.w.

 

A supportive study was performed with Hypoaspis aculeifer as test organism. In this test, the NOEC reproduction (23-d) was > 120 g a.s./ha, equivalent to 0.16 mg a.s./kg dws.

 

Additionally, four studies on Apis mellifera, three studies on Poecilus cupreus and two studies on Bombus terrestris were conducted with the substance and not with the formulated product. The LD₅₀ for honey bees ranged from 0.0037 µg a.s./L to 0.129 µg a.s./L for oral and contact exposure. The LD₅₀ for bumble bees is 0.15 µg a.s./L for oral and 0.1 µg a.s./L for contact. The mortality for carabid beetle ranged from 0% to 100% between 0.01 and 4 mg/kg dry weight soil.