Hydrocarbons, C5, n-alkanes, isoalkanes

Endpoint summary

Description of key information

There are no key skin or eye irritation studies identified for hydrocarbons C5; however, three read-across skin irritation studies were available from structural analogues, two for n-pentane and one for 2-methylbutane. These studies consisted of an animal study (OECD 401 and EU Method B.4) conducted with n-pentane and two human studies (non-guideline) conducted with either n-pentane or 2-methylbutane.  All studies indicate that petanes were not irritating in either rabbits or humans. One read-across eye irritation study (OECD 405) is available for n-pentane, in which the test material was not irritating in the eye of the rabbit. 

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

There are no key skin or eye irritation studies identified for hydrocarbons C5; however, three read-across skin irritation studies were available for structural analogues, two for n-pentane and one for 2-methylbutane. Skin and eye irritation data were not available for cyclopentane. These studies consisted of an animal study conducted with n-pentane and two human studies conducted with either n-pentane or 2-methylbutane. With regard to the animal study on n-pentane, 4 male and 2 female New Zealand White rabbits were dermally exposed to 0.5 mL of n-pentane for 4 hours to dorsal surface from the shoulder region to the lumbar region of each rabbit (Trimmer, 1990). Animals were then observed for 7 days. Irritation was scored by the Draize method of scoring. According to the study authors, n-pentane was classified as a mild dermal irritant based on the study's primary irritation index of 0.67. This classification was based on the descriptive ratings for skin irritation developed by Draize; however, the mean erythema and oedema score over 72 hours (0.5 and 0.06, respectively) would be considered non-irritating based on EU guidelines.

 

For the human studies, 30 human volunteers were dermally exposed to n-pentane or 2 -methylbutane for 24 hours, via a semi-occlusive patch. Thirty minutes after patch removal, the test sites were scored, and were scored again 24 hours after patch removal (Rue and Plaza, 1991). Test subjects remained under observation for a maximum of 4 hours after exposure. If the test material elicited severe reactions, the patches were removed. The average dermal irritation score for this test material was 0.27 on a scale from 0 to 7 for n-pentane. The average dermal irritation score for this test material was 0.33 on a scale from 0 to 7 for 2 -methylbutane. Therefore, both test substances were not likely to be irritating to humans.

 

One read-across eye irritation study is available for n-pentane (Frank, 1996). n-Pentane was tested for ocular irritation in 3 New Zealand White rabbits at a single 0.1 mL dose. Observations were made at 1, 24, 48, and 72 hours after application for indications of ocular irritation. Reactions were scored based on the Draize Standard Eye Irritation Grading Scale (Draize, 1959). n-Pentane caused ocular irritation of the conjunctiva in all three test animals. All animals showed signs of redness at 1 hour and 24 hours after the installation. In only one animal did redness persist until the 48 hour observation period; this same animal was the only one to exhibit chemosis and discharge responses (at the 1 hour interval). All 3 animals were cleared of any ocular irritation at the 72 hour observation.

 

Justification for classification or non-classification

Hydrocarbons C5 does not meet the criteria for classification as a skin irritantas defined by EU Dangerous Substances Directive 67/548/EEC or CLP EU Regulation 1272/2008 (GHS aligned) since measured mean erythema and oedema scores in read-across studies did not exceed 2 or 2.3, respectively. Hydrocarbons C5 is, however, classified under EU Dangerous Substances Directive 67/548/EEC as R66, Repeated exposure may cause skin dryness or cracking.

Hydrocarbon C5 does not meet the criteria for classification as an eye irritant as defined by EU Dangerous Substances Directive 67/548/EEC or CLP EU Regulation 1272/2008 (GHS aligned) based on read-across data from a structural analogue, n-pentane.