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Toxicity to microorganisms

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Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1987
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non- GLP study. No details on test substance purity provided, however acceptable informations.
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
other: Oxygen consumption test according to Robra
Principles of method if other than guideline:
Method: Oxygen consumption test according to Robra
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
Pseudomonas putida
Details on inoculum:
- Age of culture: 4 h
- Optical density: 0.390 at 436 nm and 1:100 dilution
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
30 min
Test temperature:
25 °C
pH:
7.3 - 7.5
Nominal and measured concentrations:
nominal: 0, 2500, 5000, 7500 and 10000 mg/L
Details on test conditions:
Type: aquatic
TEST SYSTEM
- Test vessel: glas vessels
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: not indicated
- Aeration: yes
- No. of organisms per vessel: no indicated
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Biomass loading rate: not indicated

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to Robra

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : oxygen consumption at test end


Duration:
30 min
Dose descriptor:
EC10
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Validity criteria fulfilled:
not specified
Conclusions:
The EC50 of the test substance on the inhibition of the respiration rate of microorganisms is >10000 mg/L.
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1987
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non- GLP study. No details on test substance purity provided, however acceptable informations.
Justification for type of information:
ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The structures of the target and source substances are identical and differ only with respect to the ratio of enantiomers where the target substance is a single pure L-isomer and the source substance is an equimolar mixture of L and D isomers.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target substance, L-Citronellyl nitrile, is a mono-constituent substance (EC No. 695-909-8, CAS no. 35931-93-2).
The source substance, DL-Citronellyl nitrile, is a mono-constituent substance (EC No. 257-288-8, CAS no. 51566-62-2).
The source and target substances are both of high purity with a low concentration of impurities.

3. ANALOGUE APPROACH JUSTIFICATION
The read across hypothesis is based on structural similarity where the only difference between target and source molecules is the enantiomeric ratio. In a non-chiral environment the target and source chemicals will have identical properties but in the chiral environment of living organisms the enantiomers may possess different carcinogenicity and teratogenicity (in a chiral environment, stereoisomers might experience selective absorption, protein binding, transport, enzyme interactions and metabolism, receptor interactions, and DNA binding). Therefore, as a precaution for the developmental toxicity endpoint it is suggested that the NOAEL 250 mg/kg bw/day for L-Citronellyl nitrile is used instead of 500 mg/kg bw/day, as it is not known which form is more potent in vivo. All other endpoints are considered to be acceptable for this substance assuming that 50% of the target compound is available in the test material.

4. DATA MATRIX
Please refer to the data matrix included in the read-across justification document attached in Section 13.2.
Reason / purpose:
read-across source
Qualifier:
equivalent or similar to
Guideline:
other: Oxygen consumption test according to Robra
Principles of method if other than guideline:
Method: Oxygen consumption test according to Robra
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
Pseudomonas putida
Details on inoculum:
- Age of culture: 4 h
- Optical density: 0.390 at 436 nm and 1:100 dilution
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
30 min
Test temperature:
25 °C
pH:
7.3 - 7.5
Nominal and measured concentrations:
nominal: 0, 2500, 5000, 7500 and 10000 mg/L
Details on test conditions:
Type: aquatic
TEST SYSTEM
- Test vessel: glas vessels
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: not indicated
- Aeration: yes
- No. of organisms per vessel: no indicated
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Biomass loading rate: not indicated

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to Robra

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : oxygen consumption at test end


Duration:
30 min
Dose descriptor:
EC10
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Validity criteria fulfilled:
not specified
Conclusions:
The EC50 of the test substance on the inhibition of the respiration rate of microorganisms is >10000 mg/L.

Description of key information

This endpoint was fulfilled using read across from 3,7-dimethyloct-6-enenitrile (EC 257-288-8 / CAS 51566-62-2), for which the following results were obtained. The toxicity to microorganisms was assessed using test guideline equivalent or similar to the Oxygen consumption test according to Robra. The EC50 of the test substance on the inhibition of the respiration rate of microorganisms is >10000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
10 000 mg/L

Additional information