Ethyl (S)-2-hydroxypropionate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1991-09-06 to 1995-08-10

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Exposure time 71.5 h instead of 72 h as in OECD 201 no replicates, no positive control, level of illumination lower than in OECD 201

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

Exposure time 71.5 h (instead of 72 h as in OECD 201), no replicates, no positive control, level of illumination lower than in OECD 201

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Ethyl (S)-lactate
- Batch no.: EK 355.8,
- Purity: > 97 %

Analytical monitoring:

yes

Details on sampling:

At the start of the test 50 mL samples were taken from the diluted stock solutions of the test substance yielding nominal concentrations of 0, 0.1,1.0 and 3.2 g/L.One test flask per test substance concentration, containing 100 mL diluted stock solution was incubated (without algae). At the end of the test 50 mL samples were taken, yielding the same nominal test substance concentrations as at the start of the test. All samples were taken in 50 mL glass bottles and transerred under cool conditions to the analytical department of TNO Nutrition and Food Research in Zeist.

Vehicle:

no

Details on test solutions:

The medium was prepared from concentrated stock solutions in Milli-Q filtered water. The medium was sterilized by micropore filtration. This medium contains 150 mg/L NaHCOs (not 50 mg/L as specified in the OECD guideline). Stock solutions were prepared by dissolving appropriate amounts of ethyl (S)-lactate in algal medium. From these stock solutions appropriate dilutions were prepared in algal medium to yield final concentrations of 0, 0.10, 0.32, 0.58, 1.0, 1.8 and 3.2 g/L.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

The fresh-water green alga Selenastrum capricornutum (ATCC 22662), which belongs to the order of Chlorococcales (class Chlorophyceae), was used as the test organism. The culture was supplied by the American Type Culture Collection, c/o Sales Department, 12301 Parklawn Drive, Rockville, Maryland 20852, USA. A preculture of algae in the exponential growth phase was prepared as detailed in OECD guideline no. 201.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

71.5 h

Test temperature:

23 ± 1°C

pH:

5.4–9.0

Nominal and measured concentrations:

Nominal concentrations: 0, 0.10, 0.32, 0.58, 1.0, 1.8 and 3.2 g/L
Measured concentrations only available for 0.1, 1 and 3.2 g/L: at t = 0 h: 0.11, 0.87, 2.97 g/L; at t = 71.5 h: 0.054, 0.85, 3.04 g/L (details in the table below in "any other information").

Details on test conditions:

TEST SYSTEM
- Test vessel: conical test flasks
- Material, size, fill volume: not available, 200 mL, 250 mL
- Aeration: not available
- Initial cells density: 1.0E+04 cells/mL
- Control end cells density: 174.6E+04 cells/mL
- No. of vessels per concentration (replicates): 2 (but one series was not used for the calculation; no proper algal growth had occurred probably due to contaminated test vessels.)
- No. of vessels per control (replicates): 4

GROWTH MEDIUM
- Standard medium used: not available

TEST MEDIUM / WATER PARAMETERS
Preparation of dilution water: The medium was prepared from concentrated stock solutions in Milli-Q filtered water. The medium was sterilized by micropore filtration. This medium contains 150 mg/L NaHCOs (not 50 mg/L as specified in the OECD Guideline).
Composition of algal medium:
NH4C1: 15 mg/L
MgCl2.6H2O: 12 mg/L
CaCl2.2H2O: 18 mg/L
MgSO4.7H2O: 15 mg/L
KH2PO4: 1.6 mg/L
FeCl3.6H2O: 80 µg/L
Na2EDTA.2H2O: 100 µg/L
HsBOs: 185 µg/L
MnCl2.4H2O: 415 µg/L
ZnCl2: 3 µg/L
CoCl2.6H2O: 1.5 µg/L
CuCl2.2H2O: 0.01 µg/L
Na2MoC-4.2H2O: 7 µg/L
NaHCO3: 150 mg/L
The pH of this medium after equilibration with air is approximately 8.

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: not available
- Light intensity and quality: fluorescent lamps with standard range 60-120 µmol/Sm2 (measured with a Bottemanne Weather Instruments Photosynthetic Radiometer RA200 Q).

EFFECT PARAMETERS MEASURED
- after 0, 24.5, 49.0 and 71.5 h the number of algal cells per mL in the samples was determined (Coulter Counter model TAII)
- The pH was measured at the start (medium without algae) and after 71.5 h in selected cultures. The morphology of the algae was examined visually with aid of a microscope at the start and the end of the test.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.8 except between 0.1 and 0.32 g/L (spacing factor 1.8²)
- Range finding study: yes
- Test concentrations in final test: 0, 0.10, 0.32, 0.58, 1.0, 1.8, 3.2 g/L
- Test concentrations in range finding test: 0, 0.1, 1.0, 10.2, 102 and 1016 mg/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2 200 mg/L

95% CI:

>= 1 900 - <= 2 600

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2 300 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

320 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control: yes
- Observation of abnormalities: no
- Unusual cell shape: no
- Colour differences: no
- Flocculation: no
- Adherence to test vessels: no
- Aggregation of algal cells: no
- Other: Many bacteria were found in the cultures containing test substance at the end of the test.
- Any stimulation of growth found in any treatment: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no

Table1: Measured concentrations of ethyl (S)-lactate.

Nominal concentration [mg/L]	Measured concentrations
	start		end
	mg/L	% of nominal	mg/L	% of nominal
0	<1		<1
100	110	110	54	54
1000	870	87	850	85
3200	2970	93	3040	95
Average % of nominal concentration	97		78

 

Table 2: Set of cell counts (1.0E+04 particles/mL, corrected for background) 

Time [h]	Nominal concentration [g/L]
	0	0	0.10	0.32	0.58	1.0	1.8	3.2
0	0.9	1.0	0.9	0.9	1.0	0.9	1.0	1.0
24.5	5.9	5.8	5.7	5.5	4.8	5.1	4.3	3.5
49	34.7	32.4	33.7	32.2	28.2	27.9	21.9	13.3
71.5	191.5	175.7	208.1	230.2	164.0	219.0	183.3	23.4

Validity criteria fulfilled:

yes

Conclusions:

In a short term toxicity test with algae (Selenastrum capricornutum) the following effect values were determined: EC50 = 2200 mg/L for growth inhibition and NOEC = 320 mg/L.

Executive summary:

The toxicity of ethyl (S)-lactate to the freshwater green alga Selenastrum capricornutum was determined in a growth inhibition test according to OECD guideline no. 201 and the OECD principles of Good Laboratory Practice. The test included chemical determinations of test substance concentrations during the test. The nominal concentrations of ethyl (S)-lactate tested were 0, 0.10, 0.32, 0.58, 1.0, 1.8 and 3.2 g/L. Algal growth was determined by electronic particle counting. The EC50 with respect to growth rate (ErC50) was found to be 2.2 g/L, with a 95 % confidence interval of 1.9–2.6 g/L. The EC50 with respect to the area under the growth curve (EbC50) was found to be 2.3 g/L (in the range 1.8–3.2 g/L). The no observed effect concentration (NOEC) with respect to the effects referred to above was estimated to be 0.32 g/L. An effect on the inoculum viability, as found in this test, may be expected when a substance looses its toxicity during the test, in this case probably due to biodegradation. At the start of the test approximately 97 % of the nominal test substance concentrations of 0.1, 1.0 and 3.2 g/L were found by chemical analysis. At the end of the test these percentages were lower: 54, 85 and 95 % at the concentrations analysed.

Description of key information

Ethyl (S)-lactate is practically non-toxic to algae. No hazard has been identified.

Key value for chemical safety assessment

EC50 for freshwater algae:

2 200 mg/L

EC10 or NOEC for freshwater algae:

320 mg/L

Additional information

The toxicity of ethyl (S)-lactate to the freshwater green alga Selenastrum capricornutum was determined in a growth inhibition test according to OECD guideline no. 201 and the OECD principles of Good Laboratory Practice. The test included analytical determination of test substance concentrations during the test. The nominal concentrations of ethyl (S)-lactate tested were 0, 0.10, 0.32, 0.58, 1.0, 1.8 and 3.2 g/L. Both inhibition of algal growth and biomass was determined. The effect concentrations on algal growth are used as key values. At the start of the test, 110, 87, and 93 % (average: 97 %) of the nominal test substance concentrations of 0.1, 1.0 and 3.2 g/L were recovered by chemical analysis. At the end of the test, recoveries were 54, 85 and 95 % at the concentrations analysed, respectively. Since recovery was > 80 % at the concentrations showing effects on algal growth, effect concentrations are presented as nominal concentrations.”