(±)-neomenthol

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:

key study

Study period:

Jun 01, 1991 - Jun 03, 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Remarks:

The study was performed acording to a method similar to the one described in OECD guideline No. 209 and followed the principles of GLP. However, relatively few details are provided in the study documentation.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Version / remarks:

1986

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Details on sampling:

no data

Vehicle:

not specified

Details on test solutions:

no details provided

Test organisms (species):

activated sludge

Details on inoculum:

Laboratory culture: The activated sludge was obtained on 29.05.1992 from a laboratory water treatment plant (OECD).
Pretreatment: None
Initial biomass concentration: 6 g/L dry weight

Test type:

static

Water media type:

not specified

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

no data

Hardness:

no data

Test temperature:

no data

pH:

no data

Dissolved oxygen:

no data

Salinity:

no data

Nominal and measured concentrations:

nominal concentrations: 100, 180, 320, 560, and 1000 mg/L

Details on test conditions:

Autoxidation was determined as 1000 mg/L.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

51 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

237 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

Please, see section "Any other information on results incl. tables" for the values for the inhibition of activated sludge respiration observed with different concentrations of the test item and the attached image below for a graphical presentation of the results in an inhibition vs. concentration-diagram.

Table 1: Results of the activated sludged respiration inhibition assay

Test concentration (mg/L)	Respiration rate (mg/L x h)	Inhibition (%)
100	28.3	18.7
180	20.3	41.7
320	11.3	67.5
560	7.0	79.9
1000	6.0	82.8

Validity criteria fulfilled:

yes

Remarks:

Validity of the test system was checked by a graphical evaluation of the results obtained with the reference substance.

Conclusions:

The effective concentration 50% (EC50) for inhibition of activated sludge respiration was determined as 237 mg/L. In view of this low bacteriotoxic activity, it was concluded that release of the test compound into the environment would most likely not adversely affect the natural self purification capacity of surface water bodies.

Executive summary:

The toxicity of the test item, Menthol H&R Komp., to microorganisms was tested in an activated sludge respiration assay. This assay was performed according to the ISO guideline 8192 -1986 (E), which largely resembles the OECD guideline No. 209. In this assay, The effective concentration 50% (EC50) for inhibition of activated sludge respiration by the test item was determined as 237 mg/L.

Since this value indicates a rather low bacteriotoxic activity, it was concluded that release of the test compound into the environment would most likely not adversely affect the natural self purification capacity of surface water bodies.

The validity of the test system was checked by testing a confirmed bacteriotoxic compound, 3,5-dichlorophenol, as reference substance.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Dec 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Test organisms (species):

activated sludge

Details on inoculum:

- Initial biomass concentration: 6.0 g/L (dry weight)
- laboratory scale sewage treatment plant treating synthetic sewage (OECD 209)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

19.8 °C

pH:

8.0 - 8.3

Dissolved oxygen:

O2 - Start: 5.2 - 8.4 mg
O2 - End: 3.0 - 8.2 mg

Nominal and measured concentrations:

nominal concentrations: (preliminary Test) 100, 1000 and 10000 mg/L
nominal concentrations: (primary test) 100, 180, 320, 560 and 1000 mg/L

Details on test conditions:

Type: aquatic

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorphenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

306 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

The concentrations of the test item and reference compound were not confirmed by analytical methods, but instead based on nominal concentrations

Results with reference substance (positive control):

EC50 of the reference compound 3.5-Dichlorophenol is < 20 mglL

Results:

- preliminary Test:

Test conc. [mg/l]	Respirations rate [mg/l*h]	Inhibition [%]	Referenz substance [mg/l]	Respirations rate [mg/l*h]	Inhibition [%]
100	22	0	1.0	22	0
1000	3	85	20	5	75
10000	0	100

Results:

- primary Test:

Test conc. [mg/l]	Respirations rate [mg/l*h]	Inhibition [%]	Referenz substance [mg/l]	Respirations rate [mg/l*h]	Inhibition [%]
100	19	7	1.0	22	0
180	17	19	20	5	75
320	7	67
560	4	80
1000	2	88

Validity criteria fulfilled:

yes

Remarks:

on the basic of graphic evaluation; The EC50 for 3,5-DCP was 20 mg/L and between the prescribed limits of 5 and 30 mg/L.

Conclusions:

For DL-Menthol (CAS no. 1490-04-6) an EC50 (3 h) of 306 mg/L was observed.

Executive summary:

A study with activated sludge with a duration fo 3 hours was performed according to the OECD Guideline 209. For DL-Menthol (CAS no. 1490-04-6) an EC50 of 306 mg/L was observed.

Description of key information

Activated sludge respiration inhibition EC50 (3 h) = 237 mg/L (nominal); EC10 (3 h) = 51 mg/L (nominal); read-across

Key value for chemical safety assessment

EC50 for microorganisms:

237 mg/L

EC10 or NOEC for microorganisms:

51 mg/L

Additional information

Since no data for the target substance are available, the toxicity to activated sludge microorganisms is assessed on the basis of data from two structurally similar menthols (stereo isomers).
The toxicity to microorganisms was investigated for L-menthol (CAS 2216-51-5) and an unspecified menthol isomer mixture (D/L-menthol, CAS 1490-04-6). The studies with both source substances investigated the respiration inhibition of activated sludge microorganism under standard test conditions in accordance to GLP.
In the key study with L-menthol (CAS 2216-51-5), which was conducted according to ISO 8192 (similar to OECD 209), an EC50 of 237 mg/L (nominal) and an EC10 of 51 mg/L (nominal) were determined after 3 h based on inhibition of respiration. The test system was validated using 3,5-dichlorophenol as reference substance.
This result was confirmed in the supporting study performed with the source substance D/L-menthol (CAS 1490-04-6). This study was conducted according to OECD 209 (GLP). An EC50 of 306 mg/L (nominal) was observed after 3 h of exposure.
Based on the results from two structurally related source substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) it can be concluded that testing the target substance would result in comparable results.