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

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity: short-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

03 - 14 Feb, 2006

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1735 (Whole Sediment Acute Toxicity of Invertebrates, freshwater)

Version / remarks:

Draft, 1996

Deviations:

yes

Remarks:

according to the report: temperature from 18 to 22°C, first instar of C.riparius. In comparison with OECD 218: study shorter than 28 days (10 days) so no assessment on emergence. The oxygen concentration was slightly under 60% of air saturation (min. 55%)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Subsamples of the dosing stock solutions and each treatment level and control sediments were sampled and analyzed for total [14C]residue concentration prior to the allocation of the sediments into the replicate exposure vessels and following four days of mixing and equilibration.
During the in-life phase of the definitive study, sediment, pore water and overlying water samples were removed on test days 0 and 10.
Overlying water samples were removed from the test vessels by pipetting all of the overlying water from each vessel into a graduated cylinder.
Sediment samples were collected from each centrifuge tube, following centrifugation and removal of the pore water sample. The sediment samples were transferred from the centrifuge tubes into beakers and mixed well with spatulas. A portion of the sediment was air-dried overnight in a fume hood and analyzed the following day.
Following removal of the overlying water, the pore water sample was collected by removing the entire sediment sample from each test vessel and then centrifuging for 30 minutes at 10,000 g.
The resulting pore water was removed from the centrifuge tube by pipet and its volume was measured.

Vehicle:

yes

Remarks:

acetone

Details on sediment and application:

Sediment Dosing Stock Solutions
Six individual dosing stock solutions were prepared in acetone for application of the test substance to the sediment. The following preparation scheme was used:
Volume of 0.0809 mg/mL Volume Dosing Stock
Radiolabeled Stock Used Diluted To Concentration
(mL) (mL) (mg/mL)

17 10 0.14a
6.9 10 0.056
2.7 10 0.022
1.1 10 0.0089
0.45 10 0.0036
0.17 10 0.0014
a 7.0 mL of the 0.0809 mg/mL radiolabeled stock solution was blown down under nitrogen in a volumetric flask first. A 10-mL aliquot of the 0.0809 mg/mL radiolabeled stock solution was then added to the volumetric flask to produce a 0.14 mg/mL dosing stock solution.

All resulting stock solutions were observed to be clear and colorless with no visible undissolved test substance.

Application of Test Substance to Sediment
A jar-rolling technique was used to apply the test substance to the sediment. A 9.0-mL volume of each dosing stock solution was applied to 0.0500 kg of coarse silica sand placed in glass Petri dishes. The solvent was allowed to evaporate off the sand for 30 minutes. The dry sand, containing the test substance, was then added to the 2.0000 kg of wet sediment (1.2084 kg dry weight based on a percent solids of 60.42%) in individual one-gallon jars. The total mass of sediment spiked on a dry weight basis for each treatment level and control was 1.2584 kg (0.0500 kg sand and 1.2084 kg dry weight sediment). The jars were sealed and positioned horizontally on the rolling mill. Each jar was then rolled for four hours at room temperature at approximately 15 rpm. Following the four hours of rolling, the jars were stored upright at 4C. The sediments were allowed to equilibrate for a 30-day period in the refrigerator. Once weekly during the 30-day equilibration period and prior to addition into the replicate exposure vessels (test day –1), the jars were mixed on the rolling mill for an additional two hours at room temperature to ensure the sediment was homogeneous.

Test organisms (species):

Chironomus riparius

Details on test organisms:

Prior to test initiation, egg masses were removed from culture aquaria and each individual egg mass was placed in a 30-mL plastic cup with 25 mL of culture water. The egg masses were observed daily until hatching was complete (approximately 24 to 48 hours after release of egg masses by the female midge). Hatched midge larvae were transferred to a shallow glass bowl containing 1L of culture water (laboratory well water) and 8 mL of Ankistrodesmus falcatus to serve as a substrate. Midge larvae were reared under static conditions in laboratory well water. The culture water was laboratory well water and was the same water used as overlying water during the test.
The larvae were reared in the culture bowls for three days after hatching to provide first-instar larvae for use during the exposure.
No midge mortality was observed in the test population 48 hours prior to test initiation.

Study type:

laboratory study

Test type:

semi-static

Water media type:

freshwater

Type of sediment:

natural sediment

Limit test:

no

Duration:

10 d

Exposure phase:

larvae from first generation (P)

Hardness:

46 to 50 mg/L

Test temperature:

18 to 22 ºC

pH:

Overlying water: 7.3 to 7.7
Sediment: 5.2

Dissolved oxygen:

55% and 94% saturation (5.0 mg/L at 20 ºC to 8.4 mg/L at 21 ºC)

Salinity:

Not appliacble

Ammonia:

0.31 to 1.1 mg/L

Conductivity:

140 to 170 µmhos/cm

Nominal and measured concentrations:

Nominal sediment concentrations: 0.010; 0.026; 0.064; 0.16; 0.4 and 1.0 mg/kg
Mean measured sediment concentrations: 0.007; 0.024; 0.051; 0.14; 0.34 and 0.86 mg/kg (from 70 to 93%)

Details on test conditions:

Test vessels were positioned in a water bath containing circulating water designed to maintain the test solutions at a temperature of 20 ± 1C. The test area was illuminated with fluorescent bulbs at an intensity range of 490 to 910 lux and a photoperiod of 16 hours light and 8 hours darkness.
During rearing, the midge larvae were fed a finely ground suspension of flaked fish food daily. During the test, each replicate test vessel was fed 1.5 mL of a 4.0 mg/mL flaked fish food suspension daily.
Ten replicates were maintained for each test concentration and control. Eight replicates (A - H) were used to evaluate the biological response of the test organisms. The remaining two (I and J) replicates were maintained for the purpose of chemical analysis. Each replicate vessel contained ten midge larvae, a total of 80 midges per concentration or control for the replicates maintained for monitoring the biological response. The additional replicates were maintained under the same conditions and contained test organisms, but were not used to evaluate the biological response of the test organisms.
One day prior to test initiation (day -1), the treated and control sediments were allocated to the ten replicate vessels per treatment or control (100 mL per vessel). Overlying water was gently added to each vessel and then each vessel was placed under the renewal system.

Key result

Duration:

10 d

Dose descriptor:

EC50

Effect conc.:

0.41 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

10 d

Dose descriptor:

LC50

Effect conc.:

0.49 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

Midge survival and growth observed in both the control and solvent control during this period met the minimum standard criteria established by the OPPTS Guideline (i.e., 70% survival and 0.60 mg dry weight per midge larvae). As demonstrated by the control and solvent control organism performance, the exposure system provided test conditions that were appropriate for promoting acceptable survival and growth of Chironomus riparius.

At test termination (test day 10), survival observed among midge in the 0.34 and 0.86 mg/kg treatment levels was 55 and 0%, respectively, and was statistically different compared to the survival of the pooled control organisms (90%). During the same period, midge survival observed in the 0.0070, 0.024, 0.051 and 0.14 mg/kg treatment levels was 85, 95, 94 and 88%, respectively, and was not statistically different from the survival observed in the pooled control organisms.
At test termination (test day 10), growth observed among midge in the 0.024 and 0.051 mg/kg treatment levels was 0.92 and 0.84 mg dry weight, respectively, and was not statistically different from the growth observed in the solvent control organisms (0.89 mg dry weight). Statistical analysis determined a significant difference among growth of midge in the 0.0070 mg/kg treatment level (0.71 mg dry weight) compared to the solvent control, but this was not considered a dose-related response due to the lack of statistical significance in the two higher treatment levels (0.024 and 0.051 mg/kg). Growth observed among midge in the 0.14 and 0.34 mg/kg treatment levels was 0.76 and 0.51 mg dry weight, respectively, and was statistically different from the growth observed in the solvent control organisms. No growth was observed in the 0.86 mg/kg treatment level as no midge larvae survived the 10-day exposure in this group.

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

Validity criteria fulfilled:

yes

Remarks:

according to the ones mentioned in the report.

Executive summary:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, spiked sediment study, the 10 -days EC50 for Chironomus riparius based on growth rate was 0.41 mg a.s./kg.

Description of key information

From toxicity short-term key study, the 10-day EC50 was 0.41 mg a.i./kg based on growth rate.

From toxicity long-term key study, the 28-day EC10 was 0.0004 mg a.i./L based on emergence rate.

Key value for chemical safety assessment

EC50 or LC50 for freshwater sediment:

0.41 mg/kg sediment dw

Additional information

In one study (2006), the toxicity of test substance to sediment organisms was investigated under semi-static conditions. The GLP study was conducted according to OPPTS Draft 850.1735 guideline after 10 days of exposure to spiked sediment with the test substance. Chironomus riparius were exposed to the nominal concentrations of 0.010; 0.026; 0.064; 0.16; 0.4 and 1.0 mg a.s./kg, alongside with a control and a solvent control. Mean measured concentrations from day 0 and 10 after application ranged from 70% to 93 % of nominal concentration. Based on the nominal concentration 10-day EC₅₀was 0.41 mg a.s./kg based on growth rate and 10-day LC₅₀was 0.49 mg a.s./kg based on mortality.

 

In the long-term key study (1999), the toxicity of test material to Chironomus riparius was determined in a 28 -d-static test according to BBA-method. Larvae of Chironomus riparius (2 x 25 animals per concentration) were exposed to nominal test concentrations of 0.1, 0.32, 0.56, 1.0, 1.8, 3.2 and 10 µg a.i./L. Based on this study the EC₁₀for emergence rate for Chironomus riparius was 0.65 µg/L. This value was recalculated to a mean measured concentration of EC₁₀= 0.4 µg/L.