Dimethylcyclohex-3-ene-1-carbaldehyde

Endpoint summary

Description of key information

Skin irritation / corrosion: The substance is a skin irritant based on read across from Triplal, tested in an equivalent of an in vivo OECD TG 404. The in vivo irritation study is used as a Key and overrules the in vitro corrosion study, in which the substance was tested as corrosive. Therefore Vertoliff is a skin irritant Cat. 2.

Eye irritation (OECD TG 438): irritating to eyes Cat 2

Respiratory irritation: Not a respiratory irritant.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

The skin irritation information for Vertoliff is derived from Triplal, a close analogue. First, the studies will be summarised below (in vivo irritation study with Triplal, which is the Key information and secondly the in vitro corrosion study with Vertoliff). Thereafter, the read-across justification is presented. The accompanying files are attached in the Endpoint summary as well.

Skin irritation with Triplal (OECD TG 404):

The skin irritation potential of Triplal was tested in vivo using 4 New Zealand White rabbits. Study was performed similar to OECD 404 with an observation period shorter than needed and therefore a Klimisch 2 rating was assigned. The test material was applied on the skin under a surgical patch, which was covered with elastic adhesive bandage. After an exposure period of 4 hours the patches were removed. The animals were observed at 24, 48 and 72 hours after patch removal and also later, until 7 days. The dermal effects observed at 24 hours after patch removal encompassed moderate erythema (all animals scored 2) and slight to moderate oedema (1 animal scored 2, 1 animal scored 1.5 and 2 animals scored 1). The dermal effects observed at 48 hours stayed at the same moderate erythema (all animals scored 2) and slight to moderate oedema (2 animals scored 1.5 and 2 animals scored 1). At 72 hours, oedema effects decreased (3 animals scored 1 and 1 animal scored 0.5), the erythema effects stayed at the same level (1 animal scored 2.5 and 3 animals scored 2). The last observation was made at 7 days and then there were still signs of both erythema (1 animal scored 2, 2 animals scored 1.5 and 1 animal scored 1) and oedema (3 animals scored 0.5 and 1 animal scored 0). Although the scores obtained in test animals at the time points 24/48/72 hrs were not sufficient for classification, the study was not continued until the complete disappearance of the effects (and the scores for erythema were still moderate). As a conservative approach, Triplal is classified as a skin irritant (category 2).

Skin corrosion with Vertoliff (OECD TG 431): a supporting study because the in vivo information overrules the in vitro information

The skin corrosive potential of Vertoliff was tested in vitro using the Reconstructed Human Epidermis (RHE) model after a treatment period of 3 minutes and 1 hour. The study procedures in the study were according to OECD TG 431 and GLP principles. The principle of the assay was based on the measurement of cytotoxicity in epidermal cultures following short-term exposure of the stratum corneum to the test substance by means of the colorimetric MTT reduction assay. Duplicate tissues were treated with 50 µL undiluted test item. Concurrent positive (8N potassium hydroxide) and negative (Milli-Q water) controls were included. After the exposure period, the tissues were washed with phosphate buffered saline to remove residual test item. The tissues were subsequently incubated in MTT containing medium for 3 hours. Formazan was extracted with isopropanol (overnight at room temperature) and the optical density was measured at 570 nm. Data are presented as relative viability (%) (MTT reduction in the test item treated tissues relative to negative control tissues). The relative mean viability of the test item treated tissues was 124% after 3 minute exposure and 14% after 1 hour exposure. Under the conditions of this study the test item was considered to be corrosive to the skin, because the relative mean tissue viability was just below 15% after 1 hour exposure.

The in vitro skin irritation/corrosion properties of Vertoliff can be overruled by the in vivo skin irritation information of Triplal tested in an OECD TG 404 showing slight skin irritation

Introduction:

Vertoliff showed to be corrosive in an in vitro test (Cat 1B) according to OECD TG 431) which was unexpected because generally aldehydes similar to Vertoliff are potentially skin irritants but are not corrosive (Triplal, Floral Super and Hydratropic aldehyde). When Vertoliff is really corrosive this would lead to respiratory RMMs not yet in place and therefore further information was gathered to see if the corrosion seen in the in vitro study really warrant the respiratory RMMs.

Because Triplal is used as an analogue for other human health toxicity endpoints, the skin irritation of Triplal was reviewed. Triplal’s in vivo Skin irritation according to OECD 404, Kl2 (details presented at the end of the document) showed skin irritant in vivo, the Draize scores are just below the classification cut off but after the final observation day 7, irritation is seen. Because the full reversibility in 14-days cannot be assessed, Triplal is considered a skin irritant. In addition, Triplal is an eye irritant but not causing irreversible damage.

Hypothesis: The in vivo study of Triplal reflects the (absence of) irritation /corrosion better than the in vitro corrosion study of Vertoliff and therefore the RMM protecting the respiratory tract needed for corrosion are not needed.

Available information: For Vertoliff an in vitro corrosion study is available which shows a viability of 14% and because the cut off is 15%, the substance is considered corrosive 1B. For Triplal a skin irritation test according to OECD TG 404 is available in which the scores do not meet the criteria for classification but the absence of information on the reversibility of the effects lead to classification as a skin irritant.

In view of the structural similarities between Vertoliff and Triplal, the in vivo study of Triplal can overrule the in vitro study because the in vivo test presents the real exposure conditions better than in vitro information. For Vertoliff skin irritation can be assigned instead of corrosion.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemicals are shown in the data matrix, including physico-chemical properties and toxicological information, thought relevant for skin irritation of both substances.

Purity / Impurities

Vertoliff is a multi-constituent and its constituents are all isomers.

Analogue approach justification

The analogue approach is selected here to prevent over conservative risk managements measures. The requirements for such an analogue approach are derived from Annex XI 1.5 in which the criteria for read across are laid down. Read across can be done when the similarity can be based on a common backbone and a common functional group. The analogue Triplal is selected from IFFs portfolio because for this substance in vivo skin irritation information is available to show that the in vitro corrosion information of Vertoliff is too conservative and do not warrant rigorous RMMs.

Analogue justification

Structural similarities and differences: The Vertoliff constituents and impurities are all structural isomers of each other. The methyl groups are attached at the 3,6 or the 4,6 position but the double bond is not conjugated with the aldehyde group.

Triplal has the same generic structure as Vertoliff and can be a mono or a multi-constituents but it has the methyl groups at the 2,4 or the 3,5 position but the double bond is not conjugated with the aldehyde. In view of these constituents only differing in the position on the ring the chemical structures of both substances are considered similar.

Dermal absorption: Vertoliff and Triplal will have the same absorption potential via all routes in view of the almost the same molecular structure, weight and similar physico-chemical properties.

Reactivity: The reactive functional group is the aldehyde, which shows reactivity sometimes resulting in skin irritation but almost always in skin sensitisation. The similarity in reactivity is assessed using the pKa of the acidic derivatives of the aldehyde of both substances. The pKa for both acidic counterparts of the substances is 4.84, showing similar reactivity.

Uncertainty of acute toxicity of Vertoliff using read across from Triplal: In view of the reasoning above the in vivo skin irritation information of Vertoliff can be derived from Triplal. The in vivo information better reflect the actual skin irritation than the in vitro corrosion test. In addition, eye irritation is seen but not severe eye irritation with irreversible effects.

Data matrix

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

Conclusion on skin irritation

For Vertoliff in vitro skin corrosion information is available indicating skin corrosion. Other information from a very close analogue and other aldehydes indicate that corrosion in vivo is unlikely. Therefore information from Triplal is used to finally conclude on skin irritation. Triplal is a skin irritant in an OECD TG 404 and therefore Vertoliff is a skin irritant in an in vivo situation.

Final conclusion: Vertoliff is a skin irritant.

Data matrix for the read across to Vertoliff from Triplal and using supporting information from Floral Super and Hydratropic aldehyde

Common names	Vertoliff	Triplal	Floral Super	Hydratropic aldehyde
	Target	Source	Supporting analogue	Supporting analogue
Chemical structures
CAS no of one of the components	27939-60-2	68039-49-6	71077-31-1	93-53-8
Reach registration	Registered	Registered*	Registered	Registered
Einecs number	248-742-6	943-728-2	275-174-6	202-255-5
Empirical formula	C9H14O	C9H14O	C12H20O	C9H10O
Molecular weight	138	138	180	134
Physico-chemical data	IFF measured	ECHA site*	ECHA site	ECHA site
Physical state	Liquid	Liquid	Liquid	Liquid
Melting point, ^oC	< 20	< 50
Vapour pressure, Pa	66.1 (IFF)	36 (ECHA site)	1.66	40
Water solubility, mg/L	381.8 (IFF)	910 (ECHA site)	29	1.96
Log Kow	3.1 (IFF)	2.7 (ECHA site)	4.5 (IFF)	1.96 (ECHA site)
Human health endpoints
Skin irritation	Read across	Skin irritant (OECD TG 404)	Skin irritant (OECDTG 404)	Skin irritant (OECDTG 404)^
Eye irritation	Eye irritant (OECD TG 438)	Eye irritant (similar to OECD TG 405)	Not an Eye irritant (OECDTG 405)	Eye irritant (OECD TG 405)

*https://echa.europa.eu/nl/registration-dossier/-/registered-dossier/20385

^Information from RIFM database (not on ECHA website)

 

Justification for classification or non-classification

Based on the positive results in the skin irritation and eye irritation tests, the substance needs to be classified as skin irritant (category 2) and eye irritant (category 2) according to EU CLP (EC No. 1272/2008 and its amendments). The substance is not considered a respiratory irritant in absence of human data according to EU CLP (EC No. 1272/2008 and its amendments).