(2E)-2-(4-methylbenzylidene)heptanal

Endpoint summary

Description of key information

Skin sensitisation: Skin sensitising based on read across information from Hexyl Cinnamic Aldehyde (tested similar to OECD TG 429).

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Results derived from a valid read across, with adequate and reliable documentation / justification.

Justification for type of information:

The read across justification is presented in the endpoint summary. The corresponding documentation file is also attached there.

Reason / purpose for cross-reference:

read-across source

Key result

Parameter:

EC3

Remarks:

(%)

Value:

6.6

Remarks on result:

other: Based on read across information.

Parameter:

SI

Value:

1.7

Remarks on result:

other: Dose 2.5%

Parameter:

SI

Value:

2.1

Remarks on result:

other: Dose 5%

Parameter:

SI

Value:

4.4

Remarks on result:

other: Dose 10%

Parameter:

SI

Value:

8.1

Remarks on result:

other: Dose 25%

Parameter:

SI

Value:

14.5

Remarks on result:

other: Dose 50%

Interpretation of results:

other: Skin sensitiser, Category 1B

Remarks:

according to EU CLP Regulation (EC) No. 1272/2008 and its amendments.

Conclusions:

For Acalea an EC3 of 6.6% is derived for skin sensitization based on read across information from Hexyl Cinnamic Aldehyde.

Reference 2

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1998 and 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: A published study conducted following a protocol which was the basis for establishing the corresponding guideline adopted in 2002.

Justification for type of information:

Information used for read across to Acalea.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

GLP compliance:

not specified

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

other: CBA/Ca

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan UK, Bicester, UK
- Age at study initiation: 8-16 weeks
- Weight at study initiation:no data
- Housing: in groups of 4 in metal cages on a flushing mouse rack
- Diet (e.g. ad libitum): Ad libitum; SDS PCD pelleted diet, Special Diets Services Ltd.
- Water (e.g. ad libitum): Ad libitum
- Acclimation period:no data

ENVIRONMENTAL CONDITIONS
- Temperature (°C):21+/-2
- Humidity (%):55+/-10
- Air changes (per hr):no data
- Photoperiod (hrs dark / hrs light):12/12

IN-LIFE DATES: From: To:no data

Vehicle:

acetone/olive oil (4:1 v/v)

Concentration:

0, 2.5, 5.0, 10.0, 25.0, 50.0% w/v
Solutions were prepared freshly before each application

No. of animals per dose:

4

Details on study design:

RANGE FINDING TESTS: none conducted.

MAIN STUDY Data is provided from 5 separate tests conducted in the same test laboratory within the period of 10 months.
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method:pooled
- Criteria used to consider a positive response: SI>=3 (linear interpolation)

TREATMENT PREPARATION AND ADMINISTRATION:
See further details under 'Any other information on materials and methods inc. tables'
The method used was that described by:
Kimber and Basketter. The murine local lymph node assay; collaborative studies and new directions: a commentary. Food Chem. Toxicol. 30, 165-169 (1992).

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

Three statistical models were used to derive the EC3 from the data: Linear interpolation, Quadratic regression, Richard's model. They were performed separately for each experiment/test.
Analysis of covariance was used to compare stimulation indices across experiments.

Positive control results:

Results for hexylcinnamic aldehyde are provided below.

Parameter:

SI

Value:

1.7

Remarks on result:

other: Test 1: Dose 2.5% w/v

Parameter:

SI

Value:

2.1

Remarks on result:

other: Test 1: Dose 5% w/v

Parameter:

SI

Value:

4.4

Remarks on result:

other: Test 1: Dose 10% w/v

Parameter:

SI

Value:

8.1

Remarks on result:

other: Test 1: Dose 25% w/v

Parameter:

SI

Value:

14.5

Remarks on result:

other: Test 1: Dose 50% w/v

Parameter:

SI

Test group / Remarks:

Results of 5 tests.

Remarks on result:

other: Doses: 0, 2.5, 5, 10, 25, 50% w/v Test 1: 1, 1.7, 2.1, 4.4, 8.1, 14.5 Test 2: 1, 1.7, 2.1, 2.4, 7.2, 14.1 Test 3: 1, 1.3, 2.1, 2.7, 7.8, 13.4 Test 4: 1, 2.2, 3.2, 7.1, 13.9, 17.6 Test 5: 1, 1.0, 1.4, 2.0, 8.7, 11.6

Parameter:

other: disintegrations per minute (DPM)

Test group / Remarks:

Results of 5 tests.

Remarks on result:

other: see Remark

Remarks:

5 different tests conducted: Test 1: DPM/node - 472, 786, 1002, 2054, 3841, 6844 Test 2: DPM/node - 475, 817, 998, 1127, 3396, 6698 Test 3: DPM/node - 325, 437, 685, 876, 2539, 4356 Test 4: DPM/node - 159, 355, 508, 1124, 2207, 2795 Test 5: DPM/node - 188, 192, 256, 371, 1639, 2186

There was a statistically significant (p<0.01) difference between the inter-experimental SI. This is because a higher than average SI was determined in Test 4. There was also a steeper shape in the dose-response curve for the Test no. 4 data making it a p<0.01 for the quadratic component. Both significant differences were lost when data from Test 4 were excluded from the analysis. The results from Test 4 are considered be outliers.

Table 1. EC values derived:

Test no	Linear EC3	Quadratic EC3	Richard’s EC3
1	6.6	6.9	6.9
2	11.3	9.6	11.1
3	10.6	8.7	10.4
4	4.4	4.0	3.9
5	11.5	9.2	13.1

Interpretation of results:

sensitising

Conclusions:

A EC3 between 6.6-11.5% can be derived from four different tests conducted, using three different calculation methods

Executive summary:

Hexyl cinnamaldehyde is recommended as a positive control by the OECD guideline 406 for Skin Sensitisation. As such, the response of hexyl cinnamaldehyde in the Local Lymph Node Assay from five different experiments conducted in a single laboratory over a 10 month period was analysed. Hexylcinnamaldehyde in 0, 2.5, 5, 10, 25, 50% w/v in 4:1 acetone/olive oil was administered onto the dorsal ears of mice following a protocol equivalent to the OECD guideline 429 Skin Sensitisation: Local Lymph Node Assay adopted later. Hexyl cinnamaldehyde induced a positive response in all five tests (SI>3). The pooled stimulation indices were used to calculate the EC3 values using three different statistical approaches (Linear interpolation, Quadratic regression and Richard's model) which resulted in comparable EC3 values. Excluding the results of one of the tests which was considered to be an outlier, the EC3 range for hexylcinnamaldehyde was 6.6 -11.5% under the conditions of these experiments.

Reference 3

Endpoint:

skin sensitisation: in vitro

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

First the experimental information from the source is presented, secondly HRIPT information on Acalea and thereafter the read across justification.

Hexyl Cinnamic Aldehyde in the Local Lymph Node Assay (copied from the Lead Registrant):

"Hexyl cinnamaldehyde is recommended as a positive control by the OECD guideline 406 for Skin Sensitisation. As such, the response of hexyl cinnamaldehyde in the Local Lymph Node Assay from five different experiments conducted in a single laboratory over a 10 month period was analysed. Hexylcinnamaldehyde in 0, 2.5, 5, 10, 25, 50% w/v in 4:1 acetone/olive oil was administered onto the dorsal ears of mice following a protocol equivalent to the OECD guideline 429 Skin Sensitisation: Local Lymph Node Assay adopted later. Hexyl cinnamaldehyde induced a positive response in all five tests (SI>3). The pooled stimulation indices were used to calculate the EC3 values using three different statistical approaches (Linear interpolation, Quadratic regression and Richard's model) which resulted in comparable EC3 values. Excluding the results of one of the tests which was considered to be an outlier, the EC3 range for hexylcinnamaldehyde was 6.6 -11.5% under the conditions of these experiments".

Additional available HRIPT information on Acalea: 

A Human Repeat Insult Patch Test was performed with 102 human subjects completing the study. Under the conditions of the study, 10% substance in alcohol and diethylphthalate (75:25) did not induce skin irritation and no skin sensitisation was observed.

Read across justification:

Acalea (Cas no. 84697-09-6) and its sensitizing properties using read across from Hexyl Cinnamic Aldehyde (Cas no. 165184-98-5).

Introduction and hypothesis for the read across

Acalea is an amyl cinnamic aldehyde with an additional methyl group at the para position. No relevant data on skin sensitisation is available for REACH registration. Therefore additional information is used in accordance with Article 13 of REACH where it is said thatlacking information should be generated whenever possible by means other than vertebrate animal tests, i.e. applying alternative methods such as in vitro tests, SARs, grouping and read-across. For assessing the skin sensitization potential of the substance the analogue approach is selected because for one closely related analogue, Hexyl Cinnamic Aldehyde, reliable skin sensitization data is available which can be used for read-across.

Hypothesis: Acalea has a similar skin sensitisation potential compared to Hexyl Cinnamic Aldehyde (HCA).

Available information: HCA is used as a positive control by OECD TG 406 and OECD TG 429 for Skin Sensitization. As such, HCA is recognized as a skin sensitizer and extensive data on its response in the LLNA are available. In a published report these data were combined and the HCA EC3s derived were 6.6 -11.5%. The value of 6.6% will be used here for conservative reasons.

Target and Source chemical(s):Chemical structures of Acalea and Hexyl Cinnamic Aldehyde are shown in the data matrix, including physico-chemical properties thought relevant for skin sensitisation.

Purity / Impurities:

Acalea is a mono-constituent with a purity of ≥ 90%. The impurities are all below 10%.

Analogue approach justification:

According REACH Annex XI an analogue approach and structural alert information can be used to replace testing. The result derived should be applicable for C&L and/or risk assessment and be presented with adequate and reliable documentation.

Analogue selection:In the RIFM database and the OECD Toolbox (using Tanimoto atom pairs > 60%) three closely related structures were found for possible read across: Amyl Cinnamic Aldehyde (Cas no. 122-40-7), Hexyl Cinnamic Aldehyde (HCA, Cas no. 165184-98-5) and Butyl Cinnamic Aldehyde (Cas no. 7492-44-6). In view of HCA having the same molecular formula and weight as Acalea, this substance is the preferred analogue for read across to Acalea.

Structural similarities and differences:Acalea and HCA have the same backbone and functional group: both contain a cinnamic aldehyde with an alkyl chain.The main difference is thatAcalea contains a para-substituted methyl group, which is not present in HCA and HCA has an additional methyl group in the alkyl chain.

Toxico-kinetic reasoning:Dermal absorption:Acalea and Hexyl Cinnamic Aldehyde have similar molecular weight, 216.32, and both are liquids. Also the physico-chemical properties such as log Kow values of 5.2 and 5.3 respectively, indicate that these substances will be absorbed by the skin to a similar extent. It can be seen that the water solubility of Acalea is somewhat higher than of HCA (12.7 mg/L and 1.62 mg/L, respectively) which may be due to experimental variability as based on EPISUITE predictions similar water solubility is to be expected.

Toxico-dynamic reasoning-Reactivity: Both substances can react according to a Michael Addition reaction (based on the conjugated aldehyde and double bond) and moderate electrophilicity is anticipated resulting in protein binding. This is supported with the OECD Toolbox profiler, data not shown). 

Other experimental information supporting the read across: Both substances are not skin irritants.

Remaining uncertainties:There are no remaining uncertainties in view of the reasoning above.

Data matrix:

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

Conclusions per endpoint for C&L:

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.

For Hexyl Cinnamic Aldehyde an EC3 value 6.6% is derived using a number of LLNA studies in which it is used as a positive control. In view of the analogue justification this value can also be used for Acalea.

Final conclusion on skin sensitization:

For Acalea an EC3 of 6.6 % is derived for skin sensitization. This value will be used for classification and labelling and risk assessment purposes.

Data matrix for read across to Acalea from Hexyl Cinnamic Aldehyde.

Common names	Acalea	Hexyl Cinnamic Aldehyde
Chemical structures
Empirical formula	C15H20O	C15H20O
Cas no	84697-09-6	165184-98-5 101-86-0
EC numbers	283-718-9	639-566-4
Reach registration	Registered for 2018	Registered for 2010
Molecular weight	216.32	216.32
Physico-chemical data
Physical state	Liquid	Liquid
Vapour pressure Pa (measured)	0.017	0.068 (ECHA dissemination site)
Water solubility mg/L (measured)	12.7	1.62 (ECHA dissemination site)
Water solubility mg/L (EPISUITE)	2.46 – 5.59	2.75 – 5.44
Log Kow (measured)	5.2 – 5.4	5.3 (ECHA dissemination site)
Human Health
Skin irritation	Not skin irritant (OECD 439)	Not skin irritant (EU Method B4)
Skin sensitisation animal test	EC3 = 6.6% (Read across from Hexyl Cinnamic Aldehyde)	EC3 = 6.6 – 11.5% (similar to OECD 429)

 

Justification for classification or non-classification

Skin sensitisation: Based on the derived EC3 value for skin sensitisation (6.6%), the substance has to be classified for skin sensitisation according to EU CLP (EC 1272/2008 and its amendments),Category 1B, H317: May cause an allergic skin reaction.