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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:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 533 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
1.9 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
3.5 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 2.8 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Validity criteria fulfilled:
yes
Conclusions:
The NOEC of lactic acid (pH adjusted to approximately 8) to green algae is higher than 533 mg/L actual concentration of lactate (TWA).
Executive summary:

In a 72 hour acute toxicity study, cultures of Selenastrum capricornutum (ATCC 22662) were exposed to L(+) lactic acid (80 % a.i.) at nominal concentrations of 0, 0.10, 0.33, 0.56, 1.0, 1.9 and 2.8 g/L under static conditions in accordance with the OECD 201 guideline. The NOEC and EC50 values based on growth rate were 1.9 g/L and 3.5 g/L, respectively. There were no compound related phytotoxic effects. This toxicity study is classified as acceptable and satisfies the guideline requirements for alga growth inhibition study with S. capricornutum.

Results synopsis

Test organism: Selenastrum capricornutum

Test type: Static

72-hr EbC50: > 2.8 g/L (95% C.I.: 2.24–3.52 g/L), in terms of lactic acid

72-hr NOEC: > 533 mg/L, in terms of lactic acid

Endpoint(s) effected: Growth, abnormalities of the cells

An effect on the inoculum viability, as found in this test, may be expected when a substance loses its toxicity during the test, in this case probably due to biodegradation. The concentrations quoted in this 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. The actual concentrations of lactic acid tested at the start of the test were < 0.005, 0.020–0.065, 0.44–0.62, 1.45–1.74 g/L. According to the calculated time-weighted mean (see formula below from the OECD guideline 211: TWM = (conc0 – conc1)/(LN(conc0) – (LN(conc1))) the concentrations which should be used for effect calculations are 31 mg/L, 533 mg/L, and 1620 mg/L. The EC50 and the NOEC from the test report have to be regarded as invalid, as they were calculated on the basis of nominal values. Concerning the NOEC of 1.9 g/L, the replicates with the test concentration of 1.9 g/L were not verified analytically. Therefore, no conclusion on the actual concentration can be drawn. However, the next lower concentration was assessed analytically, revealing that the NOEC is above 533 mg/L (time-weighted mean of the measured lactic acid concentration).

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Description of key information

NOEC 72 h > 533 mg/L (measured TWA)

Experiments were performed in buffered solutions; i.e., the adjusted pH of the algal medium containing different test substance concentrations (pH 7.5–8.0 at the start of the test) remained largely constant (pH 8.0–8.1,

pH 8.2–8.7 in the presence of algae) during the tests. Effects can be therefore assigned to the test substance and are not confounded with pH effects due to the acidity of lactic acid.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
533 mg/L

Additional information

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