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

Endpoint summary

Description of key information

For Methyl Ionone Alpha Extra / Beta the following results were derived:

Species	Guideline / Method	Result	Remarks
Daphnia magna	Read-across	48-h EC50: 3.7 mg/L	Key study, Rel. 2. Value derived from read-across to Ionone, methyl- (CAS# 1335 -46 -2, tested in an OECD TG 202 study).
Green algae (D. subspicatus)	Read-across	72 -h ErC50: >9.42 mg/L 72 -h NOErC: ≥9.42 mg/L	Key study, Rel. 2. Value derived from read-across to Ionone, methyl (CAS# 1335 -46 -2, tested in an OECD TG 201 study).

Additional information

The aquatic toxicity is assessed based on read-across from Ionone, methyl- to Methyl Ionone Alpha Extra / Beta. The executive summary of the source information is presented in the respective Endpoint summaries. The read-across rationale is presented below.

Aquatic toxicityof Methyl Ionone Alpha Extra / Beta based on read across from data available forIonone, methyl-(CAS# 1335-46-2, generic).

 

Introduction and hypothesis for the analogue approach

Methyl Ionone Alpha Extra / Beta is a reaction mass resulting in a multi-constituent substance belonging to the group of Ionones. These Ionones consist of a cyclohexene ring to which a C5 alkene chain is attached with a conjugated ketone bond. This substance has 2 major constituents of whichMethyl ionone alpha extrahas the higher (7779-30-8) andMethyl ionone beta(127-43-5)the lower concentration. There are five minor ones (present < 5%). For this substance noexperimental aquatic toxicity data are available.In accordance with Article 13 of REACH, lacking information can be generated by means other than experimental testing, i.e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across.For assessing the aquatic toxicity ofMethyl Ionone Alpha Extra / Beta, the analogue approach is selected because for a close structural analogue, Ionone, methyl- (CAS# 1335-46-2), experimental data is available which can be used for read across.

Hypothesis:The aquatic toxicity of Methyl Ionone Alpha Extra / Beta is the same as ofIonone, methyl-.

Available information:ForIonone, methyl-, data is availablefrom GLP guideline studies with daphnids and freshwater algae. Based on these studies the short-term effect value forIonone, methyl-is determined to be in the range of 1 - 10 mg/L. The chronic effect value is >1 mg/L. The available data for all aquatic toxicity endpoints is reliable.

In more detail:

The Daphnia test was performed according to OECD TG 202 and in compliance with GLP. Groups of daphnids (4 replicates of 5 animals) were exposed for 48 hours to test solutions ofIonone, methyl-prepared as water accommodated fractions of loading rates of 4.6, 10, 22, 46 and 100 mg/L. Test substance analysis was performed and measured concentrations determined to be 2.58, 6.52, 15.22, 17.24 and 15.99 mg/L. Mobility was recorded at the start of the test and after 24 and 48 hours exposure. Based on mobility numbers, the 48- h EC50 value was determined at 3.7 mg/L (based on measured concentrations).

The Algaetoxicity test was performedaccording to OECD TG 201 and in compliance with GLP. Cultures of freshwater green algae (D. subspicatus; initial cell density of ca. 5E+03 cells/mL), were exposed for 72 hours to test solutions ofIonone, methyl-prepared as water accommodated fractions of loading rates of 4.6, 10, 22, 46 and 100 mg/L. Test substance analysis was performed and measured concentrations determined to be 2.49, 4.45, 7.67, 9.68 and 9.42 mg/L. Chlorophyll measurements were performed throughout the test and growth rates at the different test concentrations determined. At the end of the test, no effects were seen up to the solubility limit in test medium. The 72-h ErC50 and 72-h NOErC were determined at >9.4 mg/L and ≥9.4 mg/L, respectively (based on measured concentrations).

Target chemical and source chemical(s)

Methyl Ionone Alpha Extra / Beta is a reaction mass. Its constituents and the analogue Ionone, methyl- are presented in the data matrix with information supporting the read across.

Purity and impurities

The purity range of Methyl Ionone Alpha Extra / Beta is presented in the data matrix including the purity range of the constituents. The impurities are all below 5% and are structurally similar to the constituents. One impurity is presented because it is the key constituent of the analogue Ionone, methyl -.

Analogue approach justification

According to Annex XI section 1.5, read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group.When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation, which is presented below.

Analogue selection: For Methyl Ionone Alpha Extra / Beta the substanceIonone, methyl-was selected as an analogue for read-across because in both multi-constituents the same and similar stereo isomers of methyl ionone are present at different ratios. For Ionone, methyl – aquatic toxicity information is available.

Structural similarities and differences: Methyl Ionone Alpha Extra / Beta and Ionone, methyl – constituents have the same backbone (cyclohexene ring to which methyl groups are attached) and functional group (conjugated ketone bond in an alkene chain). Differences between the constituents is that the double bond in the ring can be at different position sometimes resulting in a tri-conjugation with the ketone, which is not impacting the aquatic toxicity.

Bioavailability: Based on the physico-chemical properties similar bioavailability is expected: most importantly all constituents have comparable log Kow values (<0.5 difference).

Reactivity: Both Methyl Ionone Alpha Extra / Beta andIonone, methyl-and their constituents belong to the toxicity group of Vinyl/Allyl ketones and therefore are considered to have similar reactivity.

Uncertainty of the prediction: Conversion of the aquatic toxicity values to Methyl Ionone Alpha Extra / Beta from Ionone methyl, - is not needed because of the overlap in constituents and all have molecular weights of 206. There are no other remaining uncertainties beyond those discussed above.

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented in the data matrix below.

Conclusions on aquatic toxicity for hazard and risk assessment

For Methyl Ionone Alpha Extra / Beta, no aquatic toxicity information is available. Read-across is used to fill this data gap. When using read-across, the result derived should be applicable for C&L and/or risk assessment, and be presented with adequate and reliable documentation. This documentation is presented in the current text. For the analogue Ionone, methyl- reliable information is available for both aquatic invertebrates and algae. The lowest acute effect value is 3.7 mg/L as observed in Daphnia magna. A chronic effect value of ≥9.42 mg/L is reported in algae. No correction for log Kow or difference in molecular weight is needed and therefore the same results can be used for Methyl Ionone Alpha Extra / Beta.

Final conclusion on hazard: Methyl Ionone Alpha Extra / Beta has an EC50 for Daphnia and algae of 3.7 and > 9.42 mg/L, respectively. The chronic algae NOEC is >=9.42 mg/L

 

Data matrix supporting the read across toMethyl Ionone Alpha Extra / Beta fromIonone, methyl- for aquatic toxicity

Substance	Methyl Ionone Alpha Extra / Beta				Ionone, methyl (multi)*
		Const. Major	Const Minor	Impurity
Read-across	Target				Source
Chemical name	Reaction Mass	Methyl ionone alpha extra	Methyl ionone beta	alpha-isomethyl ionone	Italic const. are major const.
Chemical structures	Key structures presented in the next cell				Not appl.
% in product	>=40 - <=100	30-77	10-50	<5	Available in the test report
CAS	Not appl.	7779-30-8	127-43-5	127-51-5	1335-46-2 (generic)
EC No	907-713-4	231-926-5	204-843-7	204-846-3	215-635-0
REACH regist.	2018	NA	NA	Regist	Registered
MW	(206)	206	206	206	Not appl.
Phys-chem*
Appearance	Liquid	Liquid	(Liquid)	Liquid	Liquid
VP (Pa)	1.27 (exp.)	0.87	1.35	1.3	0.22-6.1 (exp.)
WS (mg/L)	46.6 (exp.)	3.33	2.58	2.98	21-44 (exp.)
Log Kow	4.7-4.9 (exp.)	4.8	4.9	4.8	4.5-5.0 (exp.)
Ecotoxicity
EC50 Daphnia in mg/L	3.7 (Read across)	3.7 (Read across)	3.7 (Read across)	3.7 (Read across)	3.7 (OECD TG 202)
EC50 Algae in mg/L	>9.4 (Read across)				>9.4 (OECDTG 201)
NOEC Algae in mg/L	>=9.4 (Read across)				>=9.4 (OECD TG 201)

ECHA site visited 30^thApril 2018; NA=Not Available; Regist=Registered; * Physico-chemical properties are calculated with EpiSuite unless stated otherwise (exp.); RA = read-across