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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
Study period:
From December 15, 2016 to May 10, 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
GLP compliance:
yes
Test organisms (species):
activated sludge
Details on inoculum:
- Source of inoculum/activated sludge: the sewage plant for domestic sewage in Veszprém, Hungary.
Water media type:
freshwater
Total exposure duration:
3 h
Nominal and measured concentrations:
The concentrations of the test item: 10, 100 and 1000 mg/L.
Details on test conditions:
- Aeration: With compressed air (about 1 L/min)
- No. of vessels per concentration (replicates): five
- No. of vessels per blank control (replicates): five
- No. of vessels per abiotic control (replicates): five
- Sludge concentration: 3 g/L
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol (3,5-DCP)
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
Results with reference substance (positive control):
The 3-hour EC50 of 3,5-Dichlorophenol was 24.94 mg/L.

Table 1. Influence of test item on oxygen consumption of activated sludge

Test group

Conc. of test item in test mix

(mg/L)

Total oxygen consumption rate (RT)

(mg O2/L/h)

Specific respiration rate (RS)

(mg O2/L/h/g/solid)

Inhib.

(%)

pH values#

Temperature (°C)

(measured in the Laboratory)*

Variation coefficient of O2 consumption rate (%)

ID

Name

start

end

 

A1

Abiotic

1000

-1.08

7.50

7.77

19.5/21.8

A2

1000

-1.32

7.47

7.74

A3

1000

-0.83

7.48

7.73

A4

1000

-1.12

7.49

7.74

A5

1000

-1.20

7.51

7.75

 

B1

Blank

0.00

37.20

24.80

7.36

8.05

19.5/21.8

6.74

B2

0.00

38.14

25.43

7.55

8.17

B3

0.00

33.84

22.56

7.75

8.15

B4

0.00

35.54

23.69

7.74

8.26

B5

0.00

32.31

21.54

7.69

8.34

 

REF1

Ref. item

1.00

30.98

20.65

9.38

7.50

8.15

19.5/21.8

REF2

3.20

29.15

19.44

14.53

7.52

8.16

REF3

10.00

29.51

19.67

13.53

7.53

8.18

REF4

32.00

10.40

6.93

67.49

7.53

8.19

 

TI1

Test item

10

34.06

22.71

0.67

7.79

8.11

19.5/21.8

TI2

100

32.79

21.86

4.25

7.73

8.14

TI3

1000

31.39

20.92

8.22

7.68

8.31

#: Individual pH values of the BOD flasks, except TI1-3, where the average values are reported

*: Minimum / Maximum temperature (°C) measured in the Laboratory, during the experiment

Validity criteria fulfilled:
yes
Conclusions:
According to OECD 209 test method, the 3-hour EC50 of CJ302 was greater than 1000 mg/L.
Executive summary:

This test using the procedures outlined in the CiToxLAB Study Plan for 16/375-27AS and OECD 209 (OECD, 2010). The results of this OECD 209 test for CJ302 show that all validity criteria were met. The 3-hour EC50 of CJ302 was greater than 1000 mg/L.

Description of key information

The 3-hour EC50 of CJ302 was greater than 1000 mg/L (OECD TG 209).

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L

Additional information

The average specific respiration rate of the blank controls was greater than 20 mg O2/L/h/g solid and the variation coefficient of oxygen uptake rate in above untreated replicates was not more than 30 %. The 3-hour EC50 of positive control substance (3,5-Dichlorophenol) was calculated to be in the range between 2 and 25 mg/L. All test validity criteria were met. Based on the results of this study, CJ302 had no inhibition effect on the total respiration rate of the microorganisms of the activated sludge at 1000 mg/L. No further testing is necessary. Therefore, the 3-hour EC50 of CJ302 was greater than 1000 mg/L.