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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:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to the appropriate OECD test guideline, and in compliance with GLP.
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
Direct addition in to test flasks.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Sludge washed once with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated. Based on this ratio, an aliquot of washed sludge was suspended in tap water to optain a concentration equivalent to 3g dry material per litre.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
Dissolved oxygen concentration measured with an oxygen electrode (BOD-flask) for about ten to fifteen minutes.
Test temperature:
21°C - 22°C
Dissolved oxygen:
At least 6.6 mg/l
Nominal and measured concentrations:
10, 32, 100, 320, 1000 mg/l nominal.
Details on test conditions:
TEST SYSTEM
- Test vessel: 1000ml glass flasks

- Aeration: Yes

- No. of vessels per concentration (replicates): One

- No. of vessels per control (replicates): One

Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
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
Remarks:
respiration rate
Results with reference substance (positive control):
EC50 25 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/min)

% Inhibition

respiration rate

Inoculum control

-

1.073

-

Inoculum control

-

1.080

-

Mean

1.077

 

 

Test substance

1000

1.310

-21.6

Test substance

320

1.265

-17.5

Test substance

100

1.177

-9.3

Test substance

32

1.116

-3.6

Test substance

10

1.090

-1.2

 

Reference substance

50

0.242

77.5

Reference substance

16

0.716

33.5

Reference substance

5

1.053

2.2

 

Validity criteria fulfilled:
yes
Conclusions:
A 3hr ASRI NOEC value of ≥1000 mg/l was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Toxicity to microorganisms: 3hr ASRI NOEC value of ≥1000 mg/l (OECD 209)

Key value for chemical safety assessment

Additional information

An activated sludge respiration inhibition 3hr NOEC value of ≥1000 mg/l was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.