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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP guideline study, a solvent was used
Reason / purpose:
reference to same study
Related information:
Composition 1
Reference:
Composition 0
Principles of method if other than guideline:
Algae inhibition test supported by the UBA (German environmental government agency)
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)
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Cremophor
Test organisms (species):
Scenedesmus sp.
Details on test organisms:
.TEST ORGANISM
- Common name: green algae, (Scenedesmus subspicatus), SAG 86.81
- Method of cultivation: Temperature: 20 °C Culturing volume: 100 ml

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
20 °C
Nominal and measured concentrations:
Nominal test concentrations (mg/l):
0.195, 0.39, 0.78, 1.5625, 3.125, 6.25 and 12.5 mg/l. Additionally, a control and a solvent control were tested in parallel.
Details on test conditions:
TEST SYSTEM
- Fill volume: 10 ml
- Initial cells density: 10000 cells/ml


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

Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
1.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: in vivo chlorophyll-a-fluorescence
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: in vivo chlorophyll-a-fluorescence
Duration:
72 h
Dose descriptor:
EC90
Effect conc.:
> 12.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: in vivo chlorophyll-a-fluorescence
During the 72 h exposure to citronellol fluorescence values were as  follows (average of 4 replicates):

Nominal test / fluorometer values after x hours
concentration /
(mg/l) / 0 h / 24 h / 48 h / 72 h /
Control / 41 / 125 / 582 / 1758 /
0.195 / 44 / 27 / 494 / 1967 /
0.39 / 44 / 57 / 447 / 1786 /
0.78 / 40 / 124 / 524 / 1731 /
1.5625 / 41 / 148 / 614 / 1278 /
3.125 / 44 / 130 / 455 / 664 /
6.25 / 44 / 121 / 316 / 284 /
12.5 / 43 / 112 / 236 / 268 /

Chemical analysis:
No chemical dose verification was performed. All values refer to nominal test concentrations of citronellol.
Endpoint:
toxicity to aquatic algae and cyanobacteria
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: Non-GLP guideline study, a solvent was used
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
Principles of method if other than guideline:
Algae inhibition test supported by the UBA (German environmental government agency)
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)
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Cremophor
Details on test organisms:
.TEST ORGANISM
- Common name: green algae, (Scenedesmus subspicatus), SAG 86.81
- Method of cultivation: Temperature: 20 °C Culturing volume: 100 ml

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
20 °C
Nominal and measured concentrations:
Nominal test concentrations (mg/l):
0.195, 0.39, 0.78, 1.5625, 3.125, 6.25 and 12.5 mg/l. Additionally, a control and a solvent control were tested in parallel.
Details on test conditions:
TEST SYSTEM
- Fill volume: 10 ml
- Initial cells density: 10000 cells/ml


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

Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
1.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: in vivo chlorophyll-a-fluorescence
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: in vivo chlorophyll-a-fluorescence
Duration:
72 h
Dose descriptor:
EC90
Effect conc.:
> 12.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: in vivo chlorophyll-a-fluorescence
During the 72 h exposure to citronellol fluorescence values were as  follows (average of 4 replicates):

Nominal test / fluorometer values after x hours
concentration /
(mg/l) / 0 h / 24 h / 48 h / 72 h /
Control / 41 / 125 / 582 / 1758 /
0.195 / 44 / 27 / 494 / 1967 /
0.39 / 44 / 57 / 447 / 1786 /
0.78 / 40 / 124 / 524 / 1731 /
1.5625 / 41 / 148 / 614 / 1278 /
3.125 / 44 / 130 / 455 / 664 /
6.25 / 44 / 121 / 316 / 284 /
12.5 / 43 / 112 / 236 / 268 /

Chemical analysis:
No chemical dose verification was performed. All values refer to nominal test concentrations of citronellol.

Description of key information

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

The effect of Citronellol on green algae was investigated in an Algae inhibition test supported by the UBA (German environmental government agency). The in vivo chlorophyll-a-fluorescence of Scenedesmus subspicatus was determined after 72 hours detecting an EC50 of 2.4 mg/l (BASF AG, 1990). 

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
2.4 mg/L

Additional information