Methylcyclohexane

Endpoint summary

Description of key information

Skin irritation: irritating (weight of evidence)
Eye irritation: not irritating (similar to OECD Guideline 405)
Respiratory irritation: no study available

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation

Three studies are available in which the skin irritating potential of methylcyclohexane has been investigated. Due to limitations in study design and/or documentation, no key study could be identified. Therefore, assessment of potential skin irritating effects following dermal exposure to methylcyclohexane was conducted in a weight of evidence approach taking into account all available data from non-standard but well-documented studies along with poorly documented reports of not assignable reliability.

In the most recent study available (Pence, 1982a), methylcyclohexane was tested for primary skin irritation in rabbits following the Draize method (Draize, J.H. (1965). Dermal Toxicity. In Appraisal of the Safety of Chemicals in Foods, Drugs and Cosmetics. The Editorial Committee of the Association of Food and Drug Officials of the United States, pp. 46-59). A group of 3 male and 3 female rabbits was exposed to 0.5 mL of the undiluted test material applied onto both the intact and abraded skin for 24 h using an occlusive dressing. The treated skin was observed for reactions after patch removal and evaluations were made at 24 and 72 h post-application.

One male animal was found dead prior to the 24 h reading, and was not replaced. At 24 h post-application, very slight erythema was noted at 4/5 intact sites and at all 5 abraded sites. At 72 h post-application, very slight erythema was noted at 1/5 intact and 1/5 abraded sites. No edema was noted in any animal at any time. The study was terminated 72 h post-application; therefore, no information on the reversibility of the skin effects still seen at the 72 h reading is available. The individual mean erythema scores over 24 and 72 h were 0.5/0.0/0.5/1.0/0.5 for each intact skin site and 0.5/0.5/0.5/0.5/1.0 for each abraded site.

In an early study, methylcyclohexane was applied to the clipped skin of one rabbit in twelve 5 mL portions at 5 min intervals within 1 h, after which the material was removed by washing with soap and water (Treon et al., 1943a). This uncovered skin procedure was done on 6 consecutive days.

Slight hypothermia and a slight loss in body weight (no further details given) were observed in the treated animal during the 6-day study period. The loss in body weight was regained within 2 days. Repeated application of methylcyclohexane to the skin of a rabbit induced local irritation and thickening. The irritation appeared on the second day and increased with successive treatments. Hardening of the skin, thickening and ulceration appeared later and the experiment was terminated after the 6th day.

Technical grade methylcyclohexane (70 % pure, containing 10% cyclohexane and 20% dimethylcyclohexane) was reported to be moderately irritating to the skin when held in contact for 24 h (Sutton, 1969). No further details on the test system and results were available.

Taken together, the available data do not provide clear evidence for but suggests a dermal irritating potential of methylcyclohexane. Very slight erythema and no edema were observed in rabbits exposed to methylcyclohexane for 24 h under occlusive conditions; the effects being fully reversible in 4/5 animals within 72 h post-application. In contrast, repeated application of methylcyclohexane induced more severe and progressing dermal effects. Technical methylcyclohexane (containing 10% cyclohexane and 20% dimethylcyclohexane) was reported to be moderately irritating. Furthermore, since methylcyclohexane is a solvent, skin defatting properties are expected. This is likewise considered a dermal adverse local effect.

Methylcyclohexane is listed in Annex VI to Regulation (EC) No 1272/2008 as a skin irritant Category 2.

Eye irritation

Methylcyclohexane was tested for primary eye irritation in 3 male and 3 female rabbits in a study following a protocol similar to OECD guideline 405 (Pence, 1982b). The test material (0.1 mL) was applied into the conjunctival sac of one eye, the other eye serving as control. The eyes were examined and scored 1, 24, 48 and 72 h as well as 4 and 7 days after application. No corneal opacity, iritis or chemosis were observed in any animal at any reading time point (all scores 0.0). Slight conjunctival redness was seen in 4/6 rabbits 1 h post-application, which persisted in only 1/6 animals at the 24 h reading. No conjunctival redness was observed at the following scoring time points. The mean conjunctivae score over 24, 48 and 72 h was 0.3 for this animal and 0.0 for the remaining 5 animals.

In another report, technical grade methylcyclohexane (70% pure, containing 10% cyclohexane and 20% dimethylcyclohexane) was stated to be slightly, transiently irritating to the eyes of rabbits (Sutton, 1969). No further details on methods and results were available.

In conclusion, the available data indicate that methylcyclohexane may cause only slight and fully reversible eye irritating effects, not sufficient for classification.

Respiratory tract

This information is not available.

Justification for selection of skin irritation / corrosion endpoint:
No study was selected, since the identified hazard is based on the weight of evidence from all available studies, physico-chemical properties and harmonised classification (Annex VI to Regulation (EC) No 1272/2008).

Justification for selection of eye irritation endpoint:
The selected study is the most adequate and reliable study based on overall quality assessment (refer to the endpoint discussion for further details).

Effects on skin irritation/corrosion: irritating

Justification for classification or non-classification

Based on the weight of evidence, the available data on the skin irritating potential of methylcyclohexane meet the criteria for classification as Skin irritant Category 2 (H315: Causes skin irritation) according to Regulation (EC) 1272/2008 and as Irritant (Xi; R38 Irritant; Irritating to skin) according to Directive 67/548/EEC.

 

CLP: Skin Irrit. 2

DSD: R38

 

The available data on the eye irritating potential of methylcyclohexane do not meet the criteria for classification according to Regulation (EC) 1272/2008 or Directive 67/548/EEC, and are therefore conclusive but not sufficient for classification.

There is no information available on the irritating potential of methylcyclohexane to the respiratory tract.