Potassium (S)-lactate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

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

pH:

Buffered solutions

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

Details on results:

By visual comparison of the measured and the calculated growth curves of algal suspensions exposed to the test substance with those of the algal controls, the no-observed-effect-concentration (NOEC) of the 80 % aqueous solution of L(+) lactic acid was estimated to be 1.9 g/L.
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 and 2.8 g/L.
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).

The EC50 with respect to inoculum viability followed by exponential growth (EeC50) was found to be 3.5 g/L, with a 95 % confidence interval of 2.8-4.4 g/L. The corresponding EeC10 and EeC90 values were 2.3 g/L and 5.4 g/L respectively. The EC50 with respect to the area under the growth curve (EbC50) was found to be > 2.8g/L. The corresponding EbC10 and EbC90 values were 2.4 g/L (in the range 1.9-2.8 g/L) and > 2.8 g/L respectively.

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

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 the report are the nominal concentrations of the test material (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: ca. 15, 57 and 73 % at the three concentrations analysed.

Validity criteria fulfilled:

yes

Conclusions:

NOEC of lactic acid to green algae is higher than 533 mg/L, based on measured concentrations of the test substance (TWM).

Executive summary:

In a 72 hour acute toxicity study, the cultures of Selenastrum capricornutum (ATCC 22662) were exposed to L(+) lactic acid (80 % aqueous formulation) 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 NOEC > 533 mg lactate/L; time weighted mean of measured lactate concentrations

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

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.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting 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

Principles of method if other than guideline:

Based on cell number compared to the control.

GLP compliance:

no

Key result

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

ca. 1 337 other: ppm

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Validity criteria fulfilled:

not specified

Conclusions:

Within testing of 18 different substances the 120-h EC50 for Nitzscheria linearis was determined at 1337 ppm.

Executive summary:

In a 120-h growth inhibition test, cultures of Nitzscheria linearis were exposed to potassium chloride. The 120-h EC₅₀ for Nitzscheria linearis was determined at 1337 ppm.

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

Potassium lactate fully dissociates into K+ ions and lactate. The ecotoxicology of potassium-S-lactate can be understood in terms of the ecotoxicology of potassium chloride and lactic acid.

ECx values were experimentally determined for the algae Selenastrum capricornutum (lactate) and Nitzschia linearis (potassium):

S. capricornutum:

NOEC (72 h) > 533 mg lactate/L (measured TWA; Hanstveit, 1992)

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 lactate since lowering pH as a result of administration of lactic acid was compensated.

Patrick et al. 1968 assessed the toxicity of potassium chloride to the diatom Nitzschia linearis, resulting in an EC₅₀ value of 1337 mg/L after 120 h, showing that no hazard is to be expected from the potassium fraction of potassium-S-lactate.

The value derived from the test following the OECD TG 201 (Hanstveit 1992) is used as key value, as the test was conducted in accordance with the OECD test guideline 201. Based on the derived threshold values from both studies, the substance would neither be classified as acutely or chronically toxic to algae and cyanobacteria in accordance with the EU CLP Regulation.

L(+) lactic acid is practically non-toxic to algae. This is an additional indication that the short-term effects observed for fish and daphnids are of a physical nature, since algae are less sensitive to pH effects than (especially) fish.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

533 mg/L

Additional information

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.