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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
For details and justification of read-across please refer to the attached report in section 13 of IUCLID.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 300 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
> 300 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
> 300 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Results with reference substance (positive control):
The EC50 of 3,5-dichlorophenol was in the accepted range of 5.1 to 30.3 mg/L. The actual values of the EC20, EC50 and EC80 for 3,5-dichlorophenol were: EC20 = 6.4 mg/L EC50 = 13.7 mg/L EC80 = 29.4 mg/L
Reported statistics and error estimates:
The concentrations of the test substance around 50 % inhibition (if such data exist) and the concentrations of the positive control are converted to log10. These values and the corresponding percentage of inhibition are subjected to linear regression analysis. These analyses are used to obtain the regression coefficients and the respective EC20, EC50 and EC80 values.

Respiration rates and inhibition of samples

Sample

Nominal Conc. (mg/L)

mg O2/L at start

mg O2/L at end

Respiration rate (mg O2/L/h)

% inhibition

Control 1

0

6.39

4.61

16.90

6.11

 

Succinic acid

7.7

7.41

5.23

17.68

1.79

19.3

7.29

5.04

18.05

-0.28

48.2

6.93

4.36

21.54

-19.66

120.6

6.74

3.97

21.53

-19.61

301.5

7.17

4.49

20.83

-15.73

Control 2

0

6.74

4.41

19.10

-6.11


3,5-DCP

5.1

7.21

4.99

16.82

6.56

12.3

8.21

7.27

8.25

54.19

30.3

8.57

8.07

4.14

76.98

Negative values indicate enhanced respiration compared to the control cultures.

Validity criteria fulfilled:
yes
Conclusions:
The 3-hour EC50 and NOEC based on respiration inhibition were > 300 mg succinic acid/L.
Executive summary:

Activated sludge obtained from a sewage treatment plant was exposed in a 3-hour respiration inhibition test to nominal concentrations of 0 (control), 7.7, 19.3, 48.2, 120.6 and 301.5 mg succinic acid/L. The test design included duplicate samples and followed the OECD 209 guideline (version 4 April 1984). Respiration rates of all samples with the test substance were in the range of 98.2–119.7 % of the control value. The 3-hour EC50 and NOEC based on respiration inhibition were therefore determined at > 300 mg succinic acid/L corresponding to 254 mg/L succinic acid.

This information is used in a read-across approach to assess the target substance succinic anhydride. For details and justification of read-across please refer to the attached report in section 13 of IUCLID.

Description of key information

The potential toxicity of succinic anhydride to aquatic microorganisms is assessed via read-across from its hydrolytic transformation product succinic acid.

Activated sludge obtained from a sewage treatment plant was exposed in a 3-hour respiration inhibition test to nominal concentrations of 0 (control), 7.7, 19.3, 48.2, 120.6 and 301.5 mg succinic acid/L. The test design included duplicate samples and followed OECD guideline 209. The 3-hour EC50 based on respiration inhibition was > 300 mg succinic acid/L. As succinic anhydride hydrolyses rapidly to succinic acid (DT50 = approx. 5 min), succinic anhydride is not expected to inhibit microbial respiration in STPs at concentrations of > 300 mg/L, corresponding to 254 mg/L succinic anhydride.

Key value for chemical safety assessment

EC50 for microorganisms:
300 mg/L

Additional information