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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
No data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The published study results were generated according to OECD guideline 201 "Alga, Growth Inhibition Test”, the EPA Guideline EG-8 and the Technical Support Document ES-5 and in compliance with GLP standards. The test substance is isobutyl-(S)-lactate, which is used for read-across. Since the test substance is the optical antipode of the target compound isobutyl-(R)-lactate and results for short-term toxicity in algae can be extrapolated, read-across is fully justified.
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
not specified
Qualifier:
according to guideline
Guideline:
other: EPA Guideline EG-8 and the Technical Support Document ES-5
Deviations:
not specified
Qualifier:
according to guideline
Guideline:
ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)
Version / remarks:
Test conditions followed ISO 8692.
Deviations:
not specified
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
not specified
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name:
- Strain: ATCC 22662
- Source (laboratory, culture collection): American Type Culture Collection, 12301 Parklawn Drive, Rockville, Maryland, U.S.A.
Test type:
static
Water media type:
not specified
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
Various lactate esters were tested over 72 and 96 h. Since not explicitly stated in the documentation, it is not clear which period was applied to isobutyl-(S)-lactate. Therefore, 72 h is assumed as a worst-case.
Test temperature:
20 ± 1 °C
pH:
8.0
Details on test conditions:
TEST SYSTEM
- Test vessel: 200 ml conical test flask
- Type: open
- Fill volume: 100 ml
- Initial cells density: 10^4 cells/ml

GROWTH MEDIUM
- Standard medium used: no
- Detailed composition if non-standard medium was used: The standard test medium was modified by adding 150 mg/L NaHCO3 and 80 mg/L Fe citrate × 3H2O for increasing buffer capacity and Fe availability for algal growth.

OTHER TEST CONDITIONS
- Adjustment of pH: pH 8.0
- Photoperiod:
- Light intensity: 80-86 µmol/s m²

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Electronic particle counter (Coulter Counter Model TAII, 100 µm aperture)
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
520 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95 % CI = 350-770
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
not specified
Remarks on result:
other: The NOEC is < 32 mg/L

The ErC50value – based to the growth rate of the algae – wass calculated using a parametric model following Kooijman. The NOEC is calculated by comparing the treatment results with the controls. In doing so, a limit of 10 % effect has been applied as significant deviation.

Validity criteria fulfilled:
not specified
Conclusions:
For S. capricornutum strain ATCC 22662, an ErC50 value (based on growth rate) of 520 mg/L (95 % CI = 350-770 mg/L) was determined. The NOEC was found to be 32 mg/L.
Executive summary:

In a 72–96 hour acute toxicity study, cultures of green algae (S. capricornutum, strain ATCC 22662) were exposed to isobutyl-S-lactate at nominal concentrations (not reported in detail) under static conditions in accordance with OECD guideline 201. The NOEC and EC50 values based on cell density were 32 and 520 mg/L, respectively. Abnormalities were not reported.

This toxicity study is classified as acceptable and satisfies the guideline requirements for algal growth inhibition studies.

Results synopsis

Test organism: Selenastrum capricornutum, strain ATCC 22662

Test type: Static

72 or 96 hr ErC50: 520 mg/L (95 % CI = 350 to 770 mg/L)

72 or 96 hr NOEC: 32 mg/L

Endpoint(s) effected: Growth rate

This result can be extrapolated to the target substance isobutyl-(R)-lactate without restrictions, which is the optical antipode of the test substance isobutyl-(S)-lactate.

Description of key information

An ErC50 value (based on growth rate) of 520 mg/L (95 % C.I. 350–770 mg/L) was determined. The NOEC was 32 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
520 mg/L
EC10 or NOEC for freshwater algae:
32 mg/L

Additional information

In 72 h and 96 h hour short-term toxicity studies, cultures of S. capricornutum (strain: ATCC 22662) were exposed to the test item under static conditions in accordance with the OECD guideline 201 (Alga, Growth Inhibition Test), the EPA guideline EG-8 and the Technical Support Document ES-5, and the ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum). The actual test duration (72 or 96 hours) for isobutyl-(S)-lactate is not apparent from the study documentation. Therefore a test period of 72 h is assumed. An ErC50 value (based on growth rate) of 520 mg/L (95 % CI = 350–770 mg/L) was determined. The NOEC was found to be 32 mg/L.

This result can be extrapolated to the target substance isobutyl-(R)-lactate without restrictions, which is the optical antipode of the test substance isobutyl-(S)-lactate.