Desmedipham

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:

2010-09-21 to 2010-10-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

1984

Deviations:

yes

Remarks:

please see "Principles of method if other than guideline" for further information.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

Principles of method if other than guideline:

Six controls are recommended in the OECD TG 209. However, the study fulfilled the validity criteria set in OECD TG 209 for coefficient of variation of oxygen uptake in the control (based on two controls), but not for oxygen uptake rate in control, but it was quite close to the required 20 mg O2/L g activated sludge/1 hour.

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Controls: Two controls (inoculated sample without test item), one at the start (control 1) and the other at the end of the test series (control 2)
- Other relevant information: Before use, the wet weight/dry weight relationship of the activated sludge was determined by drying 10 mL of sludge suspension. Subsequently, a sludge suspension of 2 g (dry weight)/L was prepared. The pH of this suspension was measured and adjusted to 6-8. 8 mL of the synthetic medium and 100 mL of activated sludge were added to the dissolved test item. The mixture was filled up with deionised water to 250 mL and aerated at 20°C ± 2°C. The exposure medium with the reference substance was prepared by adding 8 mL of the synthetic medium, 100 mL of activated sludge and a defined amount of the stock solution to achieve the test concentrations, and was filled up with deionised water to 250 mL and aerated at 20°C ± 2°C. Control vessels (inoculated sample without test item) were prepared the same way. Additional vessels to determine the physico-chemical oxygen consumption were prepared containing the test item, and the synthetic medium but no activated sludge.

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 domestic sewage treatment plant (Municipal STP Cologne-Stammheim)
- Preparation of inoculum for exposure: The sludge was settled and the supernatant was decanted. After centrifuging the sludge (15 min at 4500 rpm and 20°C) the supernatant was decanted again. Approximately 1 g of the wet sludge was dried in order to calculate the amount of wet sludge to achieve a concentration of activated sludge of 3 g/L (dry weight) suspended solids. The calculated amount of sludge was dissolved in synthetic medium and then filled up to a defined end volume with deionised water.

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Remarks on exposure duration:

Oxygen consumption was measured and recorded after an aeration time of 3 hours in all these vessels starting with control 1. Thereafter, temperature and pH were measured as well. Then the other test vessels were measured. Control 2 terminated the measurem

Test temperature:

18.8 - 19.6°C

pH:

7.3 - 7.7

Dissolved oxygen:

4.3 - 7.9 mg O2/L

Nominal and measured concentrations:

Nominal test item concentrations of 10, 100 and 1000 mg a.s./L, respectively

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Method of application: direct weighing
- Type: closed
- Material, size, headspace, fill volume: 300 mL closed Erlenmeyer flasks
- Aeration: aerated through a glass tube at 50-100 L/h with clean oil-free air
- No. of vessels per concentration (replicates): not specified
- No. of vessels per control (replicates): 2 replicates (one at the start (control 1) and the other at the end of the test series (control 2))
- No. of vessels per abiotic control (replicates): 1 physico-chemical oxygen consumption control
- Nutrients provided for bacteria: A synthetic waste water feed was prepared by dissolving the following amounts of substance per 1 litre of water; 16.0 g peptone, 11.0 g meat extract, 3.0 g urea, 0.7 g NaCl, 0.4 g CaCl2 x 2H2O, 0.2 g MgSO4 x 7H2O, and 2.8 g K2HPO4.
- Test concentration of the activated sludge: 800 mg/L suspended solids
- Incubation time: 3 hours with permanent aeration

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Oxygen consumption was measured and recorded after an aeration time of 3 .

TEST CONCENTRATIONS
- Test item concentrations: 10, 100 and 1000 mg a.s./L
- Test item concentration in physico-chemical oxygen consumption control: 1000 mg/L
- Concentration of reference compound 3,5-Dichlorophenol : 5, 10 and 20 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

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

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

Desmedipham showed 1.8% respiration inhibition of activated sludge at a test item concentration of
1000 mg/L.

Results with reference substance (positive control):

See "Attachments" in "Overall remarks, attachments" for Table 4 (Results of reference compound 3,5-Dichlorophenol)

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

Validity criteria fulfilled:

yes

Remarks:

Oxygen uptake rate (mg oxygen / 1 g activated sludge / 1 hour) was =20, the Coefficient of variation of oxygen uptake in the control was =30%, and the EC50 of the reference compound (mg/L) was in the range of 5 – 10.

Conclusions:

Desmedipham showed no statistical significant difference of respiration inhibition of activated sludge between control and test item concentrations of 10, 100 and 1000 mg a.s./L. Since there were no effects on the oxygen uptake rate in any test levels up to 1000 mg a.s./L and the control oxygen uptake rate was close to the required, the results can be considered reliable. The following endpoints were derived from this test: EC50: >1000 mg a.s./L and NOEC =1000 mg a.s./L.

Executive summary:

A study was performed to assess the toxicity of desmedipham to bacteria. The activated sludge was exposed to desmedipham at concentrations of 10, 100 and 1000 mg a.s./L. The respiration rate of each mixture was determined after aeration periods of 3 hours. Desmedipham showed 1.8% respiration inhibition of activated sludge at a test item concentration of 1000 mg a.s./L. The following endpoints were derived from this test: EC₅₀: >1000 mg a.s./L and NOEC ≥1000 mg a.s./L.

Description of key information

Toxicity to microorganisms: The activated sludge was exposed to Desmedipham for 3 hours to investigate the toxicity. The EC₅₀ was determined to be >1000 mg/L.

 

Test species	Result	Assessment	Reference
Activated sludge	3-h EC50 >1000 mg/L 3-h NOEC ≥1000 mg/L	Key study	Neuhahn (2010)

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

1 000 mg/L