Rosemary, ext.

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2014-01-20 to 2014-03-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Aerobic activated sludge (microorganisms from a domestic wastewater treatment plant) was supplied by the sewage works of Rossdorf, Germany.
The aerobic activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in tap water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried
and the ratio of wet sludge to its dry weight was determined.
Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water. This suspension was aerated overnight and was used for the experiment.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

28 d

Test temperature:

22 ± 1 °C

pH:

7.6 (measured at the start of the test ; 7.6 - 7.8 (measured at the end of the test)

Nominal and measured concentrations:

Nominal conc. 82 mg/L test substance

Details on test conditions:

The pressure decrease in the reaction vessels was measured over complete experimental phase of 28 days. The test flasks were closed gas-tight by a measuring head. Potassium hydroxide solution (45%) was used for trapping the produced carbon dioxide. The amount of O2 consumed by the activated sludge was calculated from the decrease of pressure in the reaction vessel.

Reference substance (positive control):

yes

Remarks:

benzoic acid, sodium salt

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

82 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

The curves obtained with the reference substance alone and with Rosemary oil + reference substance show no toxic effect of Rosemary oil on the micro-organisms at the test concentration.

Results with reference substance (positive control):

The reference item sodium benzoate was sufficiently degraded to 81% after 14 days and to 77% after 28 days of incubation.

Validity criteria fulfilled:

yes

Remarks:

validity criteria of the ready biodegradability guideline were met

Conclusions:

Under the conditions of the test, 82 mg/L test substance did not cause toxicity to activated sludge microorganisms.

Executive summary:

A manometric respiratory test was performed according to OECD TG 301F and in compliance with GLP. The oxygen consumption was followed for 28-days in an aerobic system inoculated with domestic activated sludge. 82 mg/L test substance (248 mg/L ThOD) was added to the test system. The toxicity control was performed with the test substance and reference substance sodium benzoate. In the procedure controls, the reference item was degraded by an average of 81% by exposure day 14. At the end of the test (day 28), the reference item was degraded by an average of 77%. In the toxicity control, the course of biodegradation over the 28-day exposure period was similar to the test substance. Within 14 days of exposure, biodegradation amounted to 50% based on the ThOD. Thus according to the test guidelines (OECD301F), the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration because biodegradation in the toxicity control was > 25% within 14 days. Under the conditions of the test, 82 mg/L test substance did not cause toxicity to activated sludge microorganisms and hence was considered the NOEC.

Description of key information

A manometric respiratory test was performed according to OECD TG 301F and in compliance with GLP. The oxygen consumption was followed for 28-days in an aerobic system inoculated with domestic activated sludge. 82 mg/L test substance (248 mg/L ThOD) was added to the test system. The toxicity control was performed with the test substance and reference substance sodium benzoate. In the procedure controls, the reference item was degraded by an average of 81% by exposure day 14. At the end of the test (day 28), the reference item was degraded by an average of 77%. In the toxicity control, the course of biodegradation over the 28-day exposure period was similar to the test substance. Within 14 days of exposure, biodegradation amounted to 50% based on the ThOD. Thus according to the test guidelines (OECDTG 301F), the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration because biodegradation in the toxicity control was > 25% within 14 days. Under the conditions of the test, 82 mg/L test substance did not cause toxicity to activated sludge microorganisms and hence was considered the NOEC.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

82 mg/L