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

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01 December 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

TI-435 Technical was not considered sufficiently soluble in water to facilitate dosing from a concentrated aqueous stock solution.
The quantities of TI-435 Technical required were weighed onto strips of aluminium foil and the strips and the test substance added to the respective test vessels which contained reverse-osmosis water and synthetic sewage. The vessels were placed in an ultrasonic bath. The contents of the vessels were subjected to ultrasonication for approximately 10 minutes to disperse the test substance homogeneously in the test medium before adding the inoculum.
Each aliquot of synthetic sewage was amended with water and the appropriate weight of test substance or volume of the reference substance stock solution. The test mixtures were completed sequentially at timed intervals by adding equal volumes of inoculum.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

A sample of activated sludge was collected from one of the return lines at Burley Menston sewage treatment works (Yorkshire Water).
The initial suspended solids concentration was 4.4040 g/L and lay above the permitted limits of 4 g ± 10% per litre. A portion was therefore diluted with de-chlorinated tap water to provide 8 L inoculum with a nominal solids content of 4 g/L. The pH of the
inoculum after dilution was 7.60 and lay within the acceptable range of pH 6 to 8. Further initial adjustment was therefore unnecessary.
The inoculum was used in the range-finder two days after the sludge sample was collected. The inoculum was maintained by aeration at all times and was fed overnight with 400 mL synthetic sewage on two occasions during the interval between collection and use.

Test type:

static

Water media type:

other: de-chlorinated tap water

Limit test:

no

Total exposure duration:

3 h

Hardness:

Not specified

Test temperature:

20.9 - 21.6°C

pH:

5.91 and then raised to 6.51

Dissolved oxygen:

No indication

Salinity:

Not applicable

Conductivity:

Not specified

Nominal and measured concentrations:

Nominal: 1, 10, 100 and 1000 mg test item/L

Details on test conditions:

The inoculum was used in the range-finder two days after the sludge sample was collected. The inoculum was maintained by aeration at all times and was fed overnight with 400 mL synthetic sewage on two occasions during the interval between collection and use.

Reference substance (positive control):

yes

Remarks:

3,5-DCP

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

TI-435 Technical did not inhibit the respiration of activated sludge at concentrations up to and including 1000 mg/L. The concentration of TI-435 Technical causing a 50% reduction in respiration rate, relative to untreated controls, could not be determined from the results of this study, but it exceeded the highest dose tested, i.e. EC50 > 1000 mg/L.

Results with reference substance (positive control):

Regression coefficient: 0.995
EC20: 3 mg/L
EC50: 8 mg/L
EC80: 26 mg/L

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

Table 1: Validity criteria for OECD 209 (2010)

Criterion from the guideline	Outcome	Validity criterion fulfilled
The blank controls (without the test substance or reference substance) oxygen uptake rate should not be less than 20 mg oxygen per one gram of activated sludge (dry weight of suspended solids) in an hour.	Lowest consumption in control is 60.5 mg O2/L/hour considering 200 mL of 4 g dw activated sludge/L, the lowest O2 uptake= 37.81 mg O2/g dw sludge/hour	Yes
The coefficient of variation of oxygen uptake rate in control replicates should not be more than 30% at the end of definitive test.	15%	Yes
EC50 of the reference substances has to lie in a specific range	3,5-DCP: 8 mg/L (total respiration)	Yes

Validity criteria fulfilled:

yes

Conclusions:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, the EC50 3h for activated sludge was > 1000 mg test item/L.

Description of key information

From the activated sludge key study, the 3-hour EC50 for microorganisms exposed to the present test material was > 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

One key study (2000) is available for toxicity towards microorganisms. In this study, the effects of the substance towards microorganisms were examined in a 3-h toxicity test with activated sludge under static conditions. The study was carried out according to GLP and OECD guideline 209. Activated sludge was exposed to nominal concentrations of 1, 10,100 and 1000 mg/L, alongside with a control. Based on nominal concentrations an EC50 of > 1000 mg/L was determined.