1-[(4-chlorophenyl)methyl]-1-cyclopentyl-3-phenylurea

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:

2001-01-17 to 2001-01-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Version / remarks:

1988

Deviations:

no

Qualifier:

equivalent or similar 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:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: direct weighing
- Controls: Two controls without test substance are included in the test design, one at the start and the other at the end of the test series.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture: mixed population of aquatic microorganisms (activated sludge).
- Name and location of sewage treatment plant where inoculum was collected: aeration tank of a waste water treatment plant treating predominantly domestic sewage (Wupper area water authority).
- Pretreatment: aeration of the activated sludge; daily feed with synthetic medium.
- pH of the suspension before application: 6.8

Test type:

static

Water media type:

not specified

Limit test:

no

Total exposure duration:

3 h

Test temperature:

19.6 - 19.8°C

pH:

7.4 - 8.1

Dissolved oxygen:

Test start: 5.2 - 6.3 mgO2/L ; test end: 2.6 - 3.2 mgO2/L.
physicochemical oxygen consumption: 8.4

Nominal and measured concentrations:

Nominal concentration of 100, 1000, and 10000 mg a.s./L.

Details on test conditions:

TEST SYSTEM
- Test substance concentration in physico-chemical oxygen consumption control (mg/L): 1000 mg/L
- Type of application: direct weighing
- Test concentration of the activated sludge: 480 mg/L suspended solid
- Incubation time: 3 hours with permanent aeration.

Reference substance (positive control):

yes

Remarks:

3.5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 0.3 mg/L

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: based on test substance aqueous solubility.

Details on results:

The pH varied between 8.0 and 8.1. The physicochemical oxygen demand was determined at the highest test concentration at a pH of 7.4.

The control respiration rates differed less than 15%. No physicochemical oxygen consumption was observed in the highest test concentration. Therefore, the 3h-EC50 for respiration inhibition of activated sludge was reported to be >10000 mg test substance/L.

The test concentrations were above the water solubility of the active substance (0.3 mg/L at 20°C). It must be assumed that the amount of test substance dosed above the aqueous solubility of the active ingredient is not bio-available and does not contribute to the exposure of the activated sludge to the test substance. Therefore, it is concluded that the 3h-EC50 for respiration inhibition of activated sludge is >0.3 mg a.s./L.

Results with reference substance (positive control):

The 3h-EC50 of the reference substance 3, 5- dichlorophenol was within the range of 5 - 30 mgl/L.

See "Attachments" in "Overall remarks, attachments" for the result tables.

Validity criteria fulfilled:

yes

Remarks:

Respiratory rate of the 2 controls differs less than 15%, respiratory rate of the controls <60 mg 02 /L * h and EC50 of the reference substance 3.5-dichlorophenol is in the range 5 - 30 mg/L.

Conclusions:

The test concentrations were above the water solubility of the active substance (0.3 mg/L at 20°C). It must be assumed that the amount of test substance dosed above the aqueous solubility of the active ingredient is not bio-available and does not contribute to the exposure of the activated sludge to the test substance. Therefore, it is concluded that the 3h-EC50 for respiration inhibition of activated sludge is >0.3 mg a.s./L.

Executive summary:

A study was performed to assess the toxicity of pencycuron (NTN 19701) to bacteria. The activated sludge was exposed to pencycuron (NTN 19701) at concentrations of 100, 1000 and 10000 mg a.s./L. The respiration rate of each mixture was determined after aeration periods of 3 hours. Pencycuron (NTN 19701) showed 8.2% respiration inhibition of activated sludge at a test item concentration of 10000 mg a.s./L. The 3h-EC₅₀ for respiration inhibition of activated sludge was >0.3 mg a.s./L.

Description of key information

A respiration inhibition study was performed to investigate the toxicity of pencycuron on activated sludge exposed to it for 3 hours. The EC₅₀ was determined to be >0.3 mg/L. 

 

Test species	Result	Assessment	Reference
Activated sludge	3-h EC50 >0.3 mg a.s./L	Key study	Müller (2001)

Key value for chemical safety assessment

EC50 for microorganisms:

0.3 mg/L