Methyl (S)-(-)-lactate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

supporting study

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

The mean blank control oxygen uptake rate exceeded 20 mg oxygen per one gram of activated sludge (dry weight of suspended solids) in an hour. The coefficient of variation of oxygen uptake in blank control replicates did not exceed 30% at the end of the definitive test. The EC50 of 3,5-dichlorophenol was in the accepted range of 2 to 25 mg/l for total respiration.
The study met the acceptability criteria prescribed by the test guidelines and was considered valid. Under the conditions of this present test ethyl-(S)-2-hydroxypropionate was not toxic to waste water (activated sludge) bacteria at 1000 mg/l (NOEC). The EC50 was above 1000 mg/L.
There was no significant oxygen uptake from abiotic processes and the result at 1000 mg/L with a nitrification inhibitor showed that the heterotrophic respiration rate was increased compared with the corresponding control.

Results with reference substance (positive control):

3,5-dichlorophenol
EC50 = 4.33 mg/L
EC50 = 6.38 mg/L

Table 1: Details on study results

	Concentration (mg/L)	Respiration rate (mg O2/L.h)	% Inhibition respiration relative to blank control
Reference substance	2	27	31
	5	17	57
	12	12	69
Test item (combined test)	10	41	-4
	100	50	-27
	1000	57	-45
		56	-42
		68	-73
Test item (limit test)	1000	66	-58
		68	-36
		63	-51

Executive summary:

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

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is found to be readily biodegradable and the applied test concentrations are in the range of concentrations that can be expected in the influent of a sewage treatment plant

Description of key information

Methyl (S)-lactate is readily biodegradable. By way of read-across to the structural analogue ethyl-(S)-lactate, that does not impair microbial respiration rates at concentrations up to the limit concentration of 1000 mg/L, it is concluded that neither methyl-(S)-lactate is non-toxic to microorganisms in the environmentally relevant concentration range. For details on the read-across approach, please refer to the read-across report attached in section 13.