clothianidin (ISO); (E)-1-(2-chloro-1,3-thiazol-5-ylmethyl)-3-methyl-2-nitroguanidine

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 Jul - 15 Sep, 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

Version / remarks:

1999

Deviations:

yes

Remarks:

Lucerne ratio C/N specified in the report. According to the current OECD guideline 216: The formation rate in mg/kg dws/day is not reported

Qualifier:

according to guideline

Guideline:

OECD Guideline 217 (Soil Microorganisms: Carbon Transformation Test)

Version / remarks:

1999

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

Sandy Loam soil was used, with a sand content between 50-75%, organic carbon 0.5-1.5% and pH of 5.5-7.5.

Soil samples corresponding to 1.2 kg soil at 40% MWHC were weighed into 2.5 L capacity plastic containers.
A stock solution was prepared by reconstituting 506 mg of test material in a total volume of 250 mL of distilled-grade water. A 10.0 mL aliquot of the stock solution was diluted to a total volume of 100 mL with distilled-grade water to give a treatment solution concentration of 0.100 mg a.i./mL, equivalent to the 5x rate. A 2.0 mL aliquot of the stock solution was diluted to a total volume of 100 mL with distilled-grade water to give a treatment solution concentration of 0.020 mg a.i./mL, equivalent to the 1x rate.
Soil replicates were treated by evenly dispensing 12.0 mL aliquots of the treatment solution over a thin layer of soil using a glass pipette. Droplet size was as small as possible and the soil was thoroughly mixed during and after treatment. Untreated soil controls were prepared by adding 12.0 mL distilled-grade water to soil in the same manner as that applied to treated soils. After treatment, soil samples in the nitrogen transformation test were amended with 0.5% (w/w) lucerne meal and thoroughly mixed.

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

20 ± 2°C

Moisture:

40% MWHC

Organic carbon content (% dry weight):

1.1

Nitrogen content (% dry weight):

0.16

Details on test conditions:

Containers were sealed with snap-top lids containing holes to maintain aeration and incubated in the dark at 20 ± 2°C for 6 days to pre-equilibrate soil to laboratory conditions.
Soil samples were incubated at 20 ± 2°C in darkness under aerobic conditions for 28 days. The soil moisture content was adjusted to 40% MWHC at weekly intervals by weight, using distilled-grade water, throughout the study.
For each test, 3 replicate soil samples were prepared at each treatment rate. At intervals of 0-3 h, 7, 14 and 28 days post-application samples of soil (ca 50 g oven dry equiv.) were removed from each replicate for analysis.
For the determination of soil respiration activity at each sample point single subsamples of soil from each soil replicate were removed for measurement of soil respiration.
For the determination of nitrate at each sample point, single subsamples of lucerne-amended soil were removed from each replicate for analysis.

Nominal and measured concentrations:

Nominal: 150 g a.i./ha equivalent to 0.2 mg a.i./kg dws and 5 times this rate, 750 g a.i./ha equivalent to 1.0 mg a.i./kg dws

Reference substance (positive control):

yes

Remarks:

dinoseb acetate

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

1 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: Nitrate concentrations

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

1 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

respiration rate

Details on results:

Soil samples used to evaluate pesticide effects were supplemented with 5.0 g glucose per kg oven dry soil equiv. prior to measuring soil respiration.
At 0-3 h, 7, 14 and 28 days post-application, the CO2 evolution were followed over a 12 h period in the glucose amended subsamples.
Levels of nitrate in soil, which had not been amended with lucerne or treated with test material, increased from 5.2 mg to 23.3 mg N./kg over the incubation period, demonstrating significant nitrification activity.

Results with reference substance (positive control):

At 0-3 h, 14 and 28 days post-application, with dinoseb acetate, the short-term substrate-induced respiration of treated soil deviated from untreated controls by greater than 25%, all of which were statistically significant.

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

Table 1: Validity criteria for OECD 216 and OECD 217 (2000)

Criterion from the guideline	Outcome	Validity criterion fulfilled
The variation of nitrate concentrations between replicate control samples should be less than ± 15%.	max RSD nitrogen content: 0.06% max RSD carbon rate: 0.04%	Yes

Validity criteria fulfilled:

not specified

Remarks:

According to the current OECD guideline the validity criteria are fullfiled, 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 NOEC (28-day) was > 1.0 mg a.s./kg dws for nitrate content and respirtaion rate of soil microorganisms.

Description of key information

The test material, applied at 0.2 and at 1 mg a.s./kg dry wt. soil, had no negative influence on nitrogen transformation carbon transformation in a sandy loam.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

1 mg/kg soil dw

Additional information

A key study investigating the toxicity of test material to N-cycle and C-cycle of soil microorganisms was available (1999). This test was conducted according to OECD guideline No. 216 and 217. The test material was incubated in the soil for 28 days at two concentration rates (150 and 750 g a.s./ha equivalent to 0.2 and 1 mg a.s./kg dws, respectively). The results found in the treatment groups regarding nitrogen concentrations and carbon transformation rates did not show any impact of this substance on soil microorganisms after 28 days.