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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Principles of method if other than guideline:
A defined amount of activated sludge is combined with synthetic medium and the respiration rate is measured. This respiration rate is compared with the ones measured in the same experiment only using test medium with different levels of the test substance. The sensitiveness of the activated sludge is checked by one experiment using 3,5-dichlorophenol in the test medium. Non-biotic oxygen consumption was examined in addition by using the highest test substance level without addition of activated sludge.
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
activated sludge: mixed population of different microorganisms
source of activated sludge: laboratory activated sludge facility, connected to sewage water supply from "südlicher Wupperverband", Germany
pre-treatment of activated sludge: none
Total exposure duration:
30 min
Remarks on exposure duration:
under permanent aeration
Test temperature:
20 +/- 2 °C
pH:
6.3 (culture solution before beginning of respiration test)
Nominal and measured concentrations:
nominal (only): 1000, 1800, 3200, 5600, 10000 mg/l
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol (97 % purity)
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
> 10 000 mg/L
Remarks on result:
other: EC50 (diethyl carbonate pure)
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
11 mg/L
Remarks on result:
other: EC50 (3,5-dichlorophenol): determined via Probit analysis, graphically determined using a half-logarithmic scale (Gauss Integral)
Test substance and control (Table 1)

Sample concentration (mg/l) amount (mg) added to 250 ml O2-start (mg O2/l) O2-end (mg O2/l) time (min) temp. (°C) pH
test substance 1000 250 6.3 4.7 4 20.0 7.4
test substance 1800 450 6.0 4.1 5 20.5 7.3
test substance 3200 800 6.5 4.9 4 20.1 7.4
test substance 5600 1400 6.3 5.2 3 20.0 7.6
test substance 10000 2500 6.4 5.5 3 19.9 7.4
control 1     5.6 4.3 3 19.7 7.7
control 2     5.5 3.5 5 21.0 7.2
abiotic O2 consumption 10000 2500 8.3 8.3 10 19.5 7.3
abiotic O2 consumption              
abiotic O2 consumption              
abiotic O2 consumption              
abiotic O2 consumption              

Reference substance 3,5-dichlorophenol (Table 1):
Sample concentration (mg/l) O2-start (mg O2/l) O2-end (mg O2/l) time (min) temp. (°C) pH
reference substance 2.5 6.5 5.4 3 19.6 7.6
reference substance 5 6.3 5.2 3 19.8 7.4
reference substance 10 8.3 7.2 6 19.6 7.3
reference substance 20 8.6 8.1 5 19.9 7.3
reference substance 40 8.8 8.5 5 20.0 7.2

Test substance and control (Table 2):
test substance concentration (mg/l) respiration rate (mg/l*h) abiotic O2 consumption (mg/l*h) respiration rate - abiotic O2 consumption (mg O2/l*h) inhibition (%)
1000 24.0 0.0 24.0 4.0
1800 22.8 0.0 22.8 8.8
3200 24.0 0.0 24.0 4.0
5600 22.0 0.0 22.0 12.0
10000 18.0 0.0 18.0 28.0
control mean value 25.0      
control 1 26.0      
control 2 24.0      

Reference substance 3,5-dichlorophenol (Table 2):
test concentration (mg/l) respiration rate (mg/l*h) inhibition (%)
2.5 22.0 12.0
5 22.0 12.0
10 11.0 56.0
20 6.0 76.0
40 3.6 85.6
Validity criteria fulfilled:
yes
Conclusions:
The acute bacteria toxicity determined via a method basically in accordance with TG OECD 209 was EC50 > 10000 mg/l.

Description of key information

Determined EC50 in toxicity-to-microorganisms study was ≥ 10000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
10 000 mg/L

Additional information

The author of the toxicity-to-microorganisms study for the test substance diethyl carbonate evaluated a EC50 > 10000 mg/L.