Reaction mass of 1-(2,6,6-trimethyl-1-cyclohexen-1-yl)pent-1-en-3-one and 1-(2,6,6-trimethyl-2-cyclohexen-1-yl)pent-1-en-3-one

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:

15.06.2000 to 14.07.2000

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Inhibition control in ready biodegradability test performed according to OECD 301F

GLP compliance:

yes

Specific details on test material used for the study:

Purity: 97.0% (carbonyl content)

Test organisms (species):

activated sludge, domestic

Details on inoculum:

Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.

Water media type:

other: deionised water containing less than 10 mg/l dissolved organic carbon.

Total exposure duration:

28 d

Test temperature:

22°C

pH:

7.36 - 8.06

Nominal and measured concentrations:

100 mg/l for test and reference substances

Details on test conditions:

Activated sludge: dry weight of suspended solids = 2.232 g/l
To obtain a concentration of 30mg/l (dry weight) in a 250 ml flask, 3.36 ml of sludge is needed (inoculum).

Reference substance (positive control):

yes

Remarks:

Sodium benzoate (purity: min 99%)

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Comparison of respiration of flasks containing test chemical + positive control and flasks containing positive control only

Details on results:

The curves obtained with the reference substance alone and with Isoraldeine 70 + reference substance show no significant toxic effect of Isoraldeine 70 on the microorganisms at the test concentration (see illustration section).

Results with reference substance (positive control):

Degradation of sodium benzoate exceeds 40% after 7 days and 65% after 14 days: the activity of the inoculum is thus verified (validity criterion).

Validity criteria fulfilled:

yes

Remarks:

Degradation of sodium benzoate exceeds 40% after 7 days and 65% after 14 days: the activity of the inoculum is thus verified (validity criterion).

Conclusions:

The toxicity of Isoraldeine 70 to microorganisms was assessed in an inhibition control of a standardised ready test performed according to OECD 301F. Isoraldeine 70 did not inhibit the degradation of the positive control, sodium benzoate, at a test concentration of 100mg/L. This concentration can be considered the NOEC for the toxicity to STP microorganisms.

ISORALDEINE 70 was a source substance used to address the biodegradation endpoint in a read-across approach. This source substance and the registered substance (target) are both members of the methyl ionone family. There are differences in their isomeric composition. The main constituents of the target substance are n-methyl-alpha-ionone (30-77%) and n-methyl-beta-ionone (10-50%) while ISORALDEINE 70 is composed of predominantly n-methy-alpha-ionone (20-30%) and iso-methyl-alpha-ionone (60-70%). Any minor components in both substances are other methyl ionone isomers.

As demonstrated in the read-across justifications for the daphnia and algae endpoints, where three source substance of varying isomeric composition were used, this family of isomeric substances exhibit similar aquatic toxicity irrespective of the isomer ratios present. Thus it is considered that the NOEC derived from the biodegradation study of ISORALDEINE 70, gives a reliable estimate of the toxicity to microorgansims of the registered substance, “Reaction mass of 1-(2,6,6-trimethyl-1-cyclohexen-1-yl)pent-1-en-3-one and 1-(2,6,6-trimethyl-2-cyclohexen-1-yl)pent-1-en-3-one”.

Description of key information

No standard microbial inhibition test data is available for the registered substance. Therefore data derived from available ready biodegradation tests is being used to derive PNEC_STP. An inhibition control was included in the biodegradation study of ISORALDEINE 70 (Rudio, 2000) which showed no toxicity at a test concentration of 100mg/L. This concentration can be considered as a NOEC for the toxicity to STP microorganisms.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

ISORALDEINE 70 was a source substance used to address the biodegradation endpoint in a read-across approach. This source substance and the registered substance (target) are both members of the methyl ionone family. There are differences in their isomeric composition. The main constituents of the target substance are n-methyl-alpha-ionone (30-77%) and n-methyl-beta-ionone (10-50%) while ISORALDEINE 70 is composed of predominantly n-methy-alpha-ionone (20-30%) and iso-methyl-alpha-ionone (60-70%). Any minor components in both substances are other methyl ionone isomers.

As demonstrated in the read-across justifications for the daphnia and algae endpoints, where three source substance of varying isomeric composition were used, this family of isomeric substances exhibit similar aquatic toxicity irrespective of the isomer ratios present. Thus it is considered that the NOEC derived from the biodegradation study of ISORALDEINE 70, gives a reliable estimate of the toxicity to microorgansims of the registered substance, “Reaction mass of 1-(2,6,6-trimethyl-1-cyclohexen-1-yl)pent-1-en-3-one and 1-(2,6,6-trimethyl-2-cyclohexen-1-yl)pent-1-en-3-one”.