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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
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
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 88.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: corrected for lactic acid content of the test material (88.2 %)
Key result
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
>= 88.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: corrected for lactic acid content of the test material (88.2 %)
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels: EC50 = 5.9 mg/L
Validity criteria fulfilled:
yes
Conclusions:
Lactic acid 88.2% does not inhibit activated sludge respiration at concentrations up to 100 mg/L test material (88.2 mg/L active substance). Inhibition was -1.1% (stimulation).
Executive summary:

The influence of lactic acid on the respiration rate of activated sludge was investigated after a contact time of 3 hours. The study procedure was based on OECD guideline 209 (adopted April 4, 1984), EEC Directive 67/548 amended November 18, 1987 (87/302), Part C, Publication No. L133, adopted May 30, 1988 and ISO Standard 8192 (1986). The batch of the test material was a clear and colourless liquid (88.2 % aqueous solution of lactic acid) that could easily be mixed with water. A stock solution of 500 mg/L was prepared by adding 126.0 mg test substance to 250 ml of Milli-RO water. A stirring period of 30 minutes was used to accelerate dissolution and to ensure homogeneity. Volumes of the stock solution corresponding to the test concentration were then added to the test media. A concentration of 100 mg/L of the test material was tested in duplicate. Optimal contact between the test substance and test medium was ensured applying continuous aeration and stirring. No significant inhibition of the respiration rate of the sludge was recorded at 100 mg test material per litre. The duplicate measurement confirmed the result of the first measurement. Therefore no further testing was needed. Since all criteria for acceptability of the test were met, this study was considered to be valid. In conclusion, under the conditions of this present test, lactic acid was not toxic to waste water (activated sludge) bacteria at a concentration of 88.2 mg/L (corrected for lactic acid content of the test material).

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

A NOEC of 88.2 mg/L (lactic acid, 3 h) was determined with the parameter of total respiration inhibition, in accordance with the OECD guideline 209.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
88.2 mg/L

Additional information

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