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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Recent GLP study

Data source

Reference Type:
study report

Materials and methods

Test guideline
according to guideline
OECD Guideline 201 (Alga, Growth Inhibition Test)
The test method was modified to involve a better buffered medium (150 mg.H NaHCOs) and the use of a parametric model (3) to calculate the effect concentrations.
GLP compliance:
not specified

Test material

Constituent 1
Reference substance name:
L-(+)-lactic acid
EC Number:
EC Name:
L-(+)-lactic acid
Cas Number:
2-hydroxypropanoic acid
Details on test material:
80% Lactic acid solution in water. Batch no. ZO 3456

Sampling and analysis

Analytical monitoring:
Details on sampling:
- Concentrations: Samples were taken at t=0 from 0, 0.1, 1.0 and 2.8 g/L nominal concentrations
- Sampling method: 250 mL bottles
- Sample storage conditions before analysis: Each sample was analysed twice (on October 2 and November 2,1991); the samples were stored in a refrigerator pending analysis.

Test organisms

Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)

Study design

Test type:
Water media type:
Limit test:
Total exposure duration:
72 h
Post exposure observation period:

Test conditions

Buffered solutions
Nominal and measured concentrations:
Nominal (test material) 0,0.1,0.33,0.56,1.0,1.9 and 2.8 g/L; nominal (active substance) 0, 0.08, 0.26, 0.45, 0.8, 1.72, 2.24 g/L; actual (active substance) <0.005, 0.020-0.065, 0.44-0.62, 1.45-1.74 g/L (for 0, 0.1, 1.0 and 2.8 mg/L nominal concentrations)
Details on test conditions:
- Test vessel:
- Type (delete if not applicable): closed
- Initial cells density: 0.9e4 cells/mL
- Control end cells density: 156e4 cells/mL
- No. of vessels per concentration (replicates):2
- No. of vessels per control (replicates): 4

- Standard medium used: yes

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [electronic particle counter]

- Spacing factor for test concentrations: 1.8
- Range finding study
- Test concentrations: 0, 0.1, 1.0, 10, 101 and 1008 mg/L
- Results used to determine the conditions for the definitive study:

Results and discussion

Effect concentrationsopen allclose all
70 h
Dose descriptor:
Effect conc.:
1.9 g/L
Basis for effect:
growth rate
70 h
Dose descriptor:
Effect conc.:
3.5 g/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
growth rate
72 h
Dose descriptor:
Effect conc.:
> 2.8 g/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
Details on results:
By visual comparison of the measured and the calculated growth curves of algal suspen- sions exposed to the test substance with those of the algal controls (see Fig. 1), the no- observed-effect-concentration (NOEC) of the 80% aqueous solution of L(+)lactic acid was estimated to be 1.9 g.1'1.
Microscopic examination of the cells at the start and end of the incubation period revealed no abnormalities, however many bacteria were found in the cultures exposed to test substance concentrations of 1.0,1.9 and2.8 g.1-1.
The pH of the algal medium containing different test substance concentrations was adjusted to the range pH 7.5-8.0 at the start of the test. It was found to remain constant (pH 8.0-8.1) during the test. In the presence of algae the pH was found to increase a little with algal cell density (pH 8.2-8.7).

Any other information on results incl. tables

Results are based on nominal concentrations.

Applicant's summary and conclusion

Validity criteria fulfilled:
NOEC of lactic acid to green algae is 1.52 g/L nominal concentration of active substance.
Executive summary:

The toxicity of a solution of about 80 % L(+)lactic acid to the fresh-water green alga Selenastrum capricornutum was determined in a growth inhibition test according to the OECD Guideline no. 201 and the OECD principles of Good Laboratory Practice. The test included chemical determinations of the test substance concentrations during the test.

The nominal concentrations of neutralized 80 % L(+)lactic acid tested were O, 0.10, 0.33, 0.56, 1.0, 1.9 and 2.8 g .H . The algal growth was detennined by electronic partiële counting. The effect values were calculated using a parametric model assuming an error proportional to the number of cells.

The EC50 with respect to inoculum viability followed by exponential growth (EeC50) was found to be 3.5 g.H, with a 95% confidence interval of 2.8-4.4 g.H. The corresponding EeC10 and EeC90 values were 2.3 g.H and 5.4 g.H respectively. The EC50 with respect to the area under the growth curve (Et>C50) was found to be > 2.8g.H.ThecorrespondingEt,C10andEfcC90valueswere2.4g.H (intherange1.9-2.8 g.H) and > 2.8 g.1-1 respectively.

The no-observed-effect-concentration (NOEC) with respect to the effects referred to above was estimated to be 1.9 g.1-1.

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.

The concentrations quoted in thij; report are the nominal concentrations of the test substance (a solution of about 80 % L(+)lactic acid) as supplied by sponsor. At the start of the test 65-82% of the nominal test substance concentrations were found by chemical analysis. At the end of the test the concentrations were considerably lower: 15,57 and 73% at the three concentrations analysed.