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

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:

29 Jan - 01 Feb, 2001

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: Commission Directive 88/302/EEC; Official Journal of the EC L 133 Part C

Version / remarks:

Commission Directive 88/302/EEC; Official Journal of the EC L 133 Part C (1988)

Deviations:

yes

Remarks:

sludge concentration, number of replicates, pH.

GLP compliance:

yes

Analytical monitoring:

no

Details on sampling:

not applicable

Vehicle:

no

Details on test solutions:

The test substance has been added to about 130 mL deionized water and stirred overnight before testing (equilibration phase).

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Type: mixed population of aquatic microorganisms.
Origin: aeration tank of a waste water treatment plant treating predominantly domestic sewage.
Because of strong respiration of the activated sludge only 0.36 g/L suspended solid (ss) were used.
Pre-treatment: aeration of the activated sludge; daily feed with synthetic medium
pH of the suspension before application 6.9

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

Not reported

Test temperature:

19.5 - 19.9°C

pH:

7.4 - 8.3

Dissolved oxygen:

5.7 - 6.5 mg O2/L

Salinity:

Not applicable

Conductivity:

Not reported

Nominal and measured concentrations:

Nominal concentrations: 1000, 1800, 3200 5600 and 10000 mg/L

Details on test conditions:

The respiration rate of an activated sludge is measured after a contact time of 3 hours with permanent aeration.

Reference substance (positive control):

yes

Remarks:

3.5-DichIorophenoI; purity of 97%

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

The test material showed 27.9 % respiration inhibition of activated sludge at a test substance concentration of 10000 mg/L.

Results with reference substance (positive control):

Toxicity of the reference substance 3.5-Dichlorophenol to bacteria: EC50 = 14 mg/L
The EC values are determined by statistical methods (probit analysis)

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

Table 1: Validity criteria for OECD 209

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 30 mg O2/L/hour considering 360 mg ss activated sludge/L, the lowest oxygen uptake per one gram of sludge (dry weight of suspended solids) /hour was about 83%.	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 substance has to lie in a specific range	3,5-DCP: 14 mg/L (total respiration)	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 3-hour EC50 for activated sludge was > 10000 mg/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:

10 000 mg/L

Additional information

A GLP-study dated 2001 is available for toxicity towards microorganisms, which was retained as key study. 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 1000, 1800, 3200 5600 and 10000 mg/L, alongside with a control. The test material resulted in 27.9 % respiration inhibition of the activated sludge at a test substance concentration of 10000 mg/L. Based on nominal concentrations an EC50 of > 1000 mg/L was determined.