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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
Study period:
2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
-Test species and strain: Pseudokirchneriella subcapitata KORSHIKOV
- Age (on study day 0): A stock algal culture is maintained continuously at the test facility. Before the exposure an inoculum culture is prepared from the stock culture and incubated for 4 days at 21 – 24 °C (max. temperature difference 2 °C). After this time, the inoculum culture is in exponential growth phase and can be used to initiate the test (study day 0).
- Supplier: Collection of algal cultures in University of Göttingen/Germany
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23.1 – 23.5 °C
pH:
7.7 - 9.5
Nominal and measured concentrations:
Nominal: 0, 4.6, 10, 22, 46 and 100 mg/L
Measured: 0, 6.5, 10.4, 18.5, 41.7 and 91.5 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type (delete if not applicable):
- Material, size, headspace, fill volume: Erlenmeyer flasks (nominal volume 250 mL) closed with glass plugs, 100 ml fill volume
- Initial cells density: 0.3 x 10E4 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6


GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16:8
- Light intensity and quality: Average 4900 lux (within ±15% variability) at a wave length of 400 - 700 nm
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
14.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
9.27 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Validity criteria fulfilled:
yes
Conclusions:
Growth rate: nominal value of EC50 on Pseudokirchneriella subcapitata is 14.5 mg/L and the EC10 is 9.27 mg/L.
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
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:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
-Test species and strain: Pseudokirchneriella subcapitata KORSHIKOV
- Age (on study day 0): A stock algal culture is maintained continuously at the test facility. Before the exposure an inoculum culture is prepared from the stock culture and incubated for 4 days at 21 – 24 °C (max. temperature difference 2 °C). After this time, the inoculum culture is in exponential growth phase and can be used to initiate the test (study day 0).
- Supplier: Collection of algal cultures in University of Göttingen/Germany
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23.1 – 23.5 °C
pH:
7.7 - 9.5
Nominal and measured concentrations:
Nominal: 0, 4.6, 10, 22, 46 and 100 mg/L
Measured: 0, 6.5, 10.4, 18.5, 41.7 and 91.5 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type (delete if not applicable):
- Material, size, headspace, fill volume: Erlenmeyer flasks (nominal volume 250 mL) closed with glass plugs, 100 ml fill volume
- Initial cells density: 0.3 x 10E4 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6


GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16:8
- Light intensity and quality: Average 4900 lux (within ±15% variability) at a wave length of 400 - 700 nm
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
14.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
9.27 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Validity criteria fulfilled:
yes
Conclusions:
Growth rate: nominal value of EC50 on Pseudokirchneriella subcapitata is 14.5 mg/L and the EC10 is 9.27 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 aquatic algae was assessed according to test guideline OECD 201. Growth rate: nomial value of EC50 on Pseudokirchneriella subcapitata is 14.5 mg/L and the EC10 is 9.27 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
14.5 mg/L
EC10 or NOEC for freshwater algae:
9.27 mg/L

Additional information