4-(2-chlorophenyl)-N-cyclohexyl-N-ethyl-5-oxo-4,5-dihydro-1H-tetrazole-1-carboxamide

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:

05 - 06 Jan 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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: Biodegradability: Test for inhibition of oxygen consumption

Version / remarks:

corresponds for the most part to the test method OECD 209

Principles of method if other than guideline:

A defined quantity of activated sludge is mixed with synthetic medium and the respiratory rate is measured. This rate is compared to those measured in test preparations with various concentrations of the test substance.

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test substance was directly weighed in. The test substance has been added to about 130 mL deionised water and stirred over night before testing (equilibration phase).

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: aeration tank of a waste water plant treating predominantly domestic sewage (Wupper area water authority, Germany)
- Pretreatment: none
- Initial biomass concentration: 480 mg/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Test temperature:

18 - 22 °C

pH:

7.7 (pH of the suspension before application)

Nominal and measured concentrations:

control, 100, 1000, and 10000 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Aeration: yes, permanent

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionsed water

Reference substance (positive control):

yes

Remarks:

3.5-dichlorophenol

Key result

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

EC50 (30 min) = 10mg/L

Reported statistics and error estimates:

The EC values are determined by statistical methods (probit analysis).

Table 1: Measured values of test substance / control

	Test concentration [mg/L]	Initial concentration [mg/250 ml]	O2-start [mg O2/L]	O2-end [mg O2/L]	Time [min.]	Temp. [°C]	pH
Test substance	100	25	5.2	2.7	5	18.9	7.7
	1000	250	5.3	2.5	6	19.5	7.9
	10000	2500	4.7	2.9	4	19.1	7.8
Control 1			4.9	2.9	4	18.9	7.7
Control 2			5.4	2.8	5	19.1	7.8
Physiochemical oxygen consumption control	10000	2500	8.0	8.0	6	19.7	7.6

Because of strong respiration of the activated sludge only 0.48 g/L SS were used.

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

 

Table 2: Measured values of reference substance

	Test concentration [mg/L]	Initial Concentration* [mg/250 ml]	O2-start [mg O2/L]	O2-end [mg O2/L]	Time [min.]	Temp. [°C]	pH
Reference substance	5	2.5	6.2	3.9	6	18.8	7.7
	10	5	6.2	4.9	5	18.7	7.7
	20	10	7.8	7.0	6	18.9	7.8

* Volume added in ml of 3.5-Dichlorophenol stock solution (500 mg/L); total volume 250 mL.

 

Table 3: Results with test substance

Test concentration [mg/L]	Respiratory rate test substance[mg/L x h]	Physiochemical oxygen consumption [mg/L x h]	Respiratory rate -Physiochemical oxygen consumption [mg/L x h]	Inhibition [%]
100	30.0	0.0*	30.0	2.0
1000	28.0	0.0*	28.0	8.5
10000	27.0	0.0	27.0	11.8
Control mean	30.6
Control 1	30.0
Control 2	31.2

*The physico chemical oxygen consumption is determined at 10000 mg/L test substance. No physico-chemical oxygen consumption has been determined. Therefore lower concentrations of the test substance cause no physico-chemical oxygen consumption (deduced values).

 

Table 4: Results with reference substance

Test concentration [mg/L]	Respiratory rate [mg/L x h]	Inhibition [%]
5	23.0	24.8
10	15.6	49.0
20	8.0	73.9

The reference substance concentration result from the quantities used in the preparations and have not been confirmed by analytical methods.

Validity criteria fulfilled:

not applicable

Description of key information

NOEC (30 min) ≥ 10000 mg/L (nominal, similar to OECD 209, activated sludge)

Additional information

One experimental study is available testing the toxicity of the substance towards aquatic microorganisms (1998). The study was conducted with activated sludge. The study procedure followed the 'Commission Directive 88/302/EEC, Official Journal of the EC L 133, Part C: Biodegradability: Test for inhibition of oxygen consumption' which corresponds for the most part to the test method OECD 209. A defined quantity of activated sludge was mixed with synthetic medium and the respiratory rate was measured over time. This rate is compared to those measured in test preparations with various concentrations of the test substance. Activated sludge was exposed to nominal test item concentrations of 100, 1000, and 10000 mg/L for 30 min. Since no respiratory inhibition was observed compared to the control a NOEC (30 min) ≥10000 mg/L was derived.