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Diss Factsheets

Ecotoxicological information

Toxicity to microorganisms

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Administrative data

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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:
guideline study
Qualifier:
according to guideline
Guideline:
other: EG-Nr. L 133/118 from 30.5.1988
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Direct addition
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Marl-Ost municipal sewage treatment plant.

- Preparation of inoculum for exposure: Centrifuged.

- Suspended solids: 3.6 g/l; (1.44 g/l when used in test).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
Oxygen consumption evaluated over a time period of at most 10 minutes.
Test temperature:
19.0 - 20.7°C
Nominal and measured concentrations:
Nominal:207.6 mg/l; 157.4 mg/l; 101 mg/l; 51.2 mg/l; 20 mg/l
Details on test conditions:
TEST SYSTEM
- Material, size, headspace, fill volume: 500 ml

- Type (delete if not applicable): closed

- Aeration: Yes
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
463 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
32.6 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):
EC50 6.9 mg/l

Table 1: Controls, reference substance (3, 5-dichlorophenol) and test substance: oxygen consumption and percentage inhibition of the respiration rate.

Flask

Nominal concentration (mg/l)

Oxygen consumption rate

(mg O2/l/hour)

% Inhibition

respiration rate

Inoculum control

-

23.93

-

Inoculum control

-

24.23

-

 

Test substance

207.6

14.84

38.4

Test substance

157.4

16.47

31.6

Test substance

101

19.73

18.1

Test substance

51.2

21.04

12.6

Test substance

20

22.50

6.6

 

Reference substance

5

13.92

42.4

Reference substance

7

11.94

50.4

Reference substance

10

9.98

58.6

 

Validity criteria fulfilled:
yes
Conclusions:
A 3-hour ASRI EC50 value of 463 mg/l and EC10 value of 32.6 mg/l were determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Toxicity to microorganisms: 3-hour ASRI EC50 463 mg/l and EC10 32.6 mg/l (EC guideline 118/133 (1988)). The EC50 and EC10 are equivalent to 364 mg/l and 26 mg/l when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

EC50 for microorganisms:
364 mg/L
EC10 or NOEC for microorganisms:
26 mg/L

Additional information

A 3-hour ASRI EC50 value of 463 mg/l and EC10 value of 32.6 mg/l were determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP (Diefenbach 1995). The results may be expressed in terms of concentration of the hydrolysis product, 3-(trihydroxysilyl)propanethiol, by applying a molecular weight correction: (MW of silanol = 154.26 / MW of parent = 196.34) * EC50 463 and EC10 32.6 = EC50 364 mg/l and EC10 26 mg/l.

Methanol does not have adverse effects on microorganisms (OECD 2004).