diuron (ISO); 3-(3,4-dichlorophenyl)-1,1-dimethylurea

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

other: Commission directive 88/302/EEC

Principles of method if other than guideline:

Corresponds to the test method OECD guideline 209: activated sludge; respiration inhibition test

GLP compliance:

yes

Analytical monitoring:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture: no
- Source: Aeration tank of sewage treatment plant treating predominantly domestic sewage
- Sampling site: Wupper area water authority, Germany
- Pretreatment: none
- Initial biomass concentration: 400 mg/L sludge

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Test temperature:

20 ±2 °C

pH:

7.3 (before application)

Nominal and measured concentrations:

Nominal: 1000, 1800, 3200, 5600 and 10000 mg/L
A blank control and a test with the reference substance 3.5-Dichlorophenol were also performed

Details on test conditions:

TEST SYSTEM
- Test vessel: no information available
- Material, size, headspace, fill volume: 250 mL culture medium
- Aeration: permanent
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: 400 mg/L sludge

EFFECT PARAMETERS MEASURED : Respiration inhibition
- Analytical parameter: oxygen measurement
- Sampling: oxygen concentration determined over a period of 4 to 9 minutes

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

30 min

Dose descriptor:

EC10

Effect conc.:

580 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

3 080 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

30 min

Dose descriptor:

other: EC25

Effect conc.:

1 280 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

30 min

Dose descriptor:

other: EC75

Effect conc.:

7 420 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: EC50 = 16.0 mg/L

Reported statistics and error estimates:

The EC values were calculated with a probit analysis

Table 1:                 Test results
Test concentration (mg/L)	Respiratory rate test substance (mg/L)	Phys. chem. O2-consumption (mg/L)	Respiratory rate-phys.chem. O2-consumption (mg/L)	Inhibition (%)
1000	24.9	0.0*	24.9	21.0%
1800	19.7	0.0	19.7	37.5%
3200	18.8	0.0	18.8	40.3%
5600	9.0	0.0	9.0	71.4%
10000	5.3	0.0	5.3	83.2%
Control, mean	31.5	-	-	-
Control 1	33.0	-	-	-
Control 2	30.0	-	-	-

Executive summary:

A toxicity test to microorganisms, corresponding to OECD guideline 209 with GLP, is available for this substance. The study is based on nominal concentrations of the test substance and the calculated, 30 minute, EC50 for respiration inhibition is 3080 mg/L. The test item is therefore has little toxic effect on activated sludge microorganisms and is not expected to inhibit the degradation activity of activated sludge.

Description of key information

Diuron is not expected to inhibit the degredation activity of activated sludge 

Additional information

A toxicity test to microorganisms, corresponding to OECD guideline 209 with GLP, is available for Diuron. The study is based on nominal concentrations of the test substance and calculated the 30 minute EC1₀ for respiration inhibition to be 580 mg/L, with an EC₅₀ of 3080 mg/L. The test item is therefore has little toxic effect on activated sludge microorganisms and is not expected to inhibit the degradation activity of activated sludge (Caspers and Mueller, 1998).