2-methylpropyl-(R)-2-hydroxypropanoate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

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):

Raphidocelis subcapitata (previous names: Pseudokirchneriella 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 E_rC₅₀value – 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 E_rC₅₀: 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 E_rC₅₀ 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 E_rC₅₀ 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.