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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Deviation between the test parameters documented and the methods according to the guideline, but scientifically acceptable.
Reason / purpose:
reference to same study
Related information:
Composition 1
Reference:
Composition 0
Qualifier:
according to
Guideline:
other: German standard, DIN 38412 Part 27
GLP compliance:
no
Test material information:
Composition 1
Analytical monitoring:
no
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test solution was prepared using 100 mg Tween 80/l as a vehicle. The highest test concentration, 10000 mg test substance/l (nominal), was prepared using 100 mg/l Tween 80 as a solvent. The test solution was then stirred for one hour at 25 °C. The corresponding required test concentrations were prepared by taking appropriate volumes of the stirring test solution (10000 mg/l).
Test organisms (species):
Pseudomonas putida
Details on inoculum:
Pseudomonas putida, DSM 50026
Age of the bacterial suspension: 70 h
E (436 nm/1 cm): 0.400 at a dilution of 1:100
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
30 min
Nominal and measured concentrations:
Nominal test concentrations (mg/l): 78.13, 156.25, 312.5, 625, 1250, 2500, 5000 and 10000 mg/l. A blank control (containing medium only) and a solvent control (containing Tween 80) were also tested in parallel.
Details on test conditions:
TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Total volume: 100 ml 5 ml Glucose: (198 g/l) 95 ml: Test substance solution 2 - 3 ml Bacterial suspension (the volume of the suspension is dependent on the oxygen consumption of the control, should be 1.5 - 2.5 mg/l minimum)
The test solution was aerated for 30 minutes at 22 +/- 2 °C.
Duration:
30 min
Dose descriptor:
EC10
Effect conc.:
580 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
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
Remarks:
respiration rate
Duration:
30 min
Dose descriptor:
other: EC90
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Deviation between the test parameters documented and the methods according to the guideline, but scientifically acceptable.
Justification for type of information:
ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that source substances and target substance have similar physical-chemical properties and (eco)toxicological properties because they are either stereoisomers of the target substance, are hydrolysed to the same substance or their chemical structure differs only by an additional double bond. This prediction is supported by data on the substances themselves.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target substance, L-Citronellol, is a mono-constituent substance (EC No. 231-415-7, CAS no. 7540-51-4 consisting of a C8 carbon backbone, methyl substituents at C3 and C7, one double bond and a hydroxyl group. The substance is optically active, comprising a single, pure enantiomeric laevo form.

The source substance, DL-Citronellol, is a mono-constituent substance (EC No. 203-375-0, CAS no. 106-22-9, consisting of a C8 carbon backbone, methyl substituents at C3 and C7, one double bond and a hydroxyl group. The substance is an equimolar mixture of two optical isomers (enantiomers).

The source substance, citronellyl acetate, is a mono-constituent substance (EC No. 205-775-0, CAS no. 150-84-5) consisting of a C8 carbon backbone, methyl substituents at C3 and C7, one double bond and an acetate group.

The source substance, geraniol and it’s isomer, consist of a C8 carbon backbone, methyl substituents at C3 and C7, two double bonds and a hydroxyl group. The only difference between the isomers is the position of the first double bond.

The source substance, geraniol and nerol, is a multi-constituent substance of E/Z isomers (EC No. 906-125-5). The constituents consist of a C8 carbon backbone, methyl substituents at C3 and C7, two double bonds and a hydroxyl group.

The source substance, geraniol, is a mono-constituent substance (EC No. 203-377-1, CAS no. 106-24-1), consisting of a C8 carbon backbone, methyl substituents at C3 and C7, two double bonds and a hydroxyl group. Geraniol is a pure form of the E-isomer.

The source substance, nerol, is a mono-constituent substance (EC No. 203-378-7, CAS no. 106-25-2), consisting of a C8 carbon backbone, methyl substituents at C3 and C7, two double bonds and a hydroxyl group. Nerol is a pure form of the Z-isomer.
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 source substances only differ in the enantiomeric ratio or an additional double bond. Another source substance is expected to be hydrolysed to the same structure as the target substance.
In a non-chiral environment the target and source chemical DL-Citronellol 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). All endpoints read-across from DL-Citronellol are considered to be acceptable for this substance assuming that 50% of the target compound is available in the test material.
The source substance citronellyl acetate is read-across from as part of a weight of evidence approach in the repeated dose toxicity endpoint. As this substance is hydrolysed to Citronellol within 2 hours, this read-across endpoint is acceptable in the weight of evidence approach used.
The source substances geraniol, nerol and the reaction mass of geraniol/nerol differ from the target substance only by an additional double bond at C2. These structures are considered to represent a worst case scenario due to the additional potential reactive feature of the second double bond. The genotoxicity, repeated dose and reproductive toxicity endpoints read-across from these substances are therefore acceptable as a worst case assumption.

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
Related information:
Composition 1
Reference:
Composition 0
Qualifier:
according to
Guideline:
other: German standard, DIN 38412 Part 27
GLP compliance:
no
Test material information:
Composition 1
Analytical monitoring:
no
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test solution was prepared using 100 mg Tween 80/l as a vehicle. The highest test concentration, 10000 mg test substance/l (nominal), was prepared using 100 mg/l Tween 80 as a solvent. The test solution was then stirred for one hour at 25 °C. The corresponding required test concentrations were prepared by taking appropriate volumes of the stirring test solution (10000 mg/l).
Test organisms (species):
Pseudomonas putida
Details on inoculum:
Pseudomonas putida, DSM 50026
Age of the bacterial suspension: 70 h
E (436 nm/1 cm): 0.400 at a dilution of 1:100
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
30 min
Nominal and measured concentrations:
Nominal test concentrations (mg/l): 78.13, 156.25, 312.5, 625, 1250, 2500, 5000 and 10000 mg/l. A blank control (containing medium only) and a solvent control (containing Tween 80) were also tested in parallel.
Details on test conditions:
TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Total volume: 100 ml 5 ml Glucose: (198 g/l) 95 ml: Test substance solution 2 - 3 ml Bacterial suspension (the volume of the suspension is dependent on the oxygen consumption of the control, should be 1.5 - 2.5 mg/l minimum)
The test solution was aerated for 30 minutes at 22 +/- 2 °C.
Duration:
30 min
Dose descriptor:
EC10
Effect conc.:
580 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
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
Remarks:
respiration rate
Duration:
30 min
Dose descriptor:
other: EC90
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate

Description of key information

This endpoint was read across from Citronellol (3,7-dimethyl-6-Octen-1-ol, CAS 106 -22 -9).

There is one guideline study on the toxicity of Citronellol to Pseudomonas putida available. A potential respiration inhibition induced in

Pseudomonas putida by the substance was tested in compliance with German standard, DIN 38412 Part 27. An EC10 of 580 mg/l (EC50> 10000 mg/l) was determined after 30 minutes of incubation (BASF AG, 1988).

Key value for chemical safety assessment

EC50 or LC50 for microorganisms:
10 000 mg/L
EC10, LC10 or NOEC for microorganisms:
580 mg/L

Additional information