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Toxicity to microorganisms

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Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
1997
Justification for type of information:
Data from the mono-constituent anthraquinone dye Solvent violet 36
Reason / purpose:
read-across source
Key result
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Validity criteria fulfilled:
yes
Conclusions:
Solvent Green 28 showed 7.4 % respiration inhibition of activated sludge at the highest test item concentration (10000 mg/L) and an EC50 of higher than 10000 mg/L was determined. Test concentrations are given as nominal concentrations.
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1997
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Justification for type of information:
For Solvent green 28 read-across from the chronic daphnia toxicity study of Solvent violet 36 (CAS 82-16-6), which belongs to the same category, is possible.
Reason / purpose:
read-across: supporting information
Qualifier:
according to
Guideline:
other: German standard method "Amtsblatt der EG L 133 Teil C: Biologische Abbaubarkeit: Pruefung der Atmungshemmung"
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
not applicable
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Type: activated sludge
- Origin: laboratory scale sewage treatment unit (3L) treating predominantly municipal sewage. (Location: Southern Wupperverband/Germany)
- no pretreatment
- pH: 7.3
- biomass concentration: 480.0 mg/L
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
30 min
Hardness:
no data
Test temperature:
19.6-19.7°C
pH:
7.1 - 7.2
Dissolved oxygen:
O2 - Start: 5.0-5.9 mg/L
O2 - End: 2.7-3.2 mg/L
Salinity:
n.a.
Conductivity:
no data
Nominal and measured concentrations:
100, 1000, 10000 mg/L (nominal concentration)
Details on test conditions:
EXPOSURE CONDITIONS:
- Test item concentration/s: 100, 1000 and 10000 mg/L
- Test item concentration in physico-chemical oxygen consumption control: 10000 mg/L
- Concentration of reference compound : 5, 10 and 20 mg/L

The test item and reference compound concentrations were not confirmed by analytical methods, they were based on nominal concentrations.

- Test vessels: 300 mL glass Erlenmeyer flasks
- Method of application: direct weighing
- Test concentration of the activated sludge: 480 mg/L dry weight
- Test temperature: 20 ± 2°C
- Incubation time: 30 minutes with permanent aeration
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol (Purity 97 %)
Key result
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
The concentrations of the test item and reference compound were not confirmed by analytical methods, but instead based on nominal concentrations.
Results with reference substance (positive control):
For 3,5-Dichlorophenol an EC50 of 9.2 mg/L has been determined.
The EC50 value was calculated, using Probit–analysis, from the inhibition of the respiration rates at different concentrations.
Validity criteria fulfilled:
yes
Remarks:
on the basic of graphic evaluation: the EC50 for 3,5-DCP was 8.8 mg/L and between the prescribed limits of 2 and 25 mg/L
Conclusions:
Solvent Green 28 showed 7.4 % respiration inhibition of activated sludge at the highest test item concentration (10000 mg/L) and an EC50 of higher than 10000 mg/L was determined. Test concentrations are given as nominal concentrations.
Executive summary:

A study with activated sludge was performed according to the German standard method "Amtsblatt der EG L 133 Teil C: Biologische Abbaubarkeit: Prüfung der Atmungshemmung", which is equivalent to the OECD Guideline 209. Two controls without test item were included in the test design, one at the start and the other at the end of the test series. Each batch of activated sludge was checked using 3,5-Dichlorophenol as a reference compound. The physico-chemical oxygen consumption control should be carried out, since some substances may consume oxygen by chemical reactivity. In order to be able to differentiate between physico-chemical oxygen consumption and biological oxygen consumption (respiration), at least the maximum concentration of the test item was additionally tested without activated sludge. To measure the oxygen consumption, 250 mL of sludge with test item (or control or reference compound) was incubated for 3 h in 300 mL closed Erlenmeyer flasks (with air inlet and outlet) and aerated through a glass tube at 50-100 L/h with clean oil-free air. For measurement, the content of the Erlenmeyer flasks was completely transferred to 250 mL BOD bottles and O2-content was measured with an O2-meter (redox electrode) with writer. The respiration rate for each concentration was determined graphically from the linear part of the curve of O2-content versus time. The inhibitory effect of the test item at a particular concentration is expressed as a percentage of the mean of the respiration rates of two controls. The sludge was exposed to three different nominal concentrations (100, 1000, 10000 mg/L) of Solvent Green 28. Because of the strong oxygen consumption of the activated sludge, only 0.48 g/L was used in all batches. The respiration rate of each mixture was determined after aeration period of 30 min. Solvent Green 28 showed 7.4 % respiration inhibition of activated sludge at the highest test item concentration of 10000 mg/L. An EC50 >= 10000 mg/L was determined. Test concentrations are given as nominal concentrations and were not confirmed by analytical methods. This toxicity study is classified as acceptable and satisfies the guideline requirements for the toxicity study to microorganisms.

Description of key information

In a grouping approach data from Solvent violet 36 are used for Solvent green 28. The study showed 7.4 % respiration inhibition of activated sludge at the highest test item concentration (10000 mg/L) and an EC50 of higher than 10000 mg/L was determined. Test concentrations are given as nominal concentrations.

Key value for chemical safety assessment

EC50 for microorganisms:
10 000 mg/L

Additional information

"Should read: EC50 > 10000 mg/L"