Hexacos-1-ene

Endpoint summary

Description of key information

Ten key skin irritation studies (OECD 404) were identified for linear alpha olefins.  The available data indicate that C6 to C24-28 linear alpha olefins, including hexacos-1-ene, are mildly irritating to skin but do not meet the quantitative criteria for classification as skin irritants. 
Read-across eye irritation studies (FHSLA recommendations) from dec-1-ene and hexadec-1-ene were identified; both studies showed that the respective test material was not irritating to the eyes of rabbits.

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

Twenty-six skin irritation studies were identified for linear alpha olefins. For the purpose of hazard identification, only ten of these were considered key (Klimisch scores =1) because they adhered to the current OECD 404 guidelines (4 hour exposure, semi-occlusive conditions) with mean scores for erythema and oedema averaged over 24, 48, and 72 hours. These ten studies were conducted with the following substances: hex-1-ene, oct-1-ene, dec-1-ene, dodec-1-ene, tetradec-1-ene, hexadec-1-ene, and octadec-1-ene. The remaining studies, using occlusive methods and/or skin contact times exceeding 4 hours duration, were considered less reliable since the exposure conditions were more stringent than guideline and likely therefore to yield unrepresentative results.

  

One key skin irritation study was identified for each of the following substances: hex-1-ene, oct-1-ene, and dec-1-ene. The application of hex-1-ene to rabbit skin produced no dermal effects with a mean irritation score of 0 for erythema and oedema at all time points (Price, 1985) while the treatment of rabbit skin with oct-1-ene produced mean erythema and oedema scores of 1.9 and 1.1, respectively (Driscoll, 1999b). Mild-to-moderate, reversible dermal effects were also noted following application of dec-1-ene to rabbit skin; reported mean irritation scores for erythema and oedema were 2.0 and 1.7, respectively (Driscoll, 1996c). 

 

Dodec-1-ene was evaluated for potential skin irritation effects in two studies. In the first, treatment with Gulftene 12 resulted in mean irritation scores of 2.2 for erythema and 2.4 for oedema (averaged over 24, 48, and 72 hours) with crust formation observed at the 14-day observation(Driscoll, 1996d). In the second study, dodec-1-ene produced slight to moderate erythema and slight oedema, both of which decreased with time until fully reversible by day 10. The mean erythema and oedema scores were 1.44 and 0.78, respectively (Merkel, 2002b).

Tetradec-1-ene was also evaluated in two skin irritation studies. In the first study, well–defined erythema and slight oedema was observed 24 hours post-exposure but had receded by 48 hours with desquamation noted at 72 hours. The test material produced mean scores of 1.3 for erythema formation and 1.1 for oedema (Driscoll, 1996a). In the second study, all rabbits were free of dermal irritation 72 hours post-exposure. The mean erythema score was 0.56 and the mean oedema score was 0.22 (Merkel, 2002a).

Two key skin irritation studies also were identified for the higher carbon number linear alpha olefins, hexadec-1-ene and octadec-1-ene. In a study with hexadec-1-ene, application of GULFTENE 16 to rabbit skin produced slight irritant effects; the mean score for erythema over 72 hours was 1.3 while the mean score for oedema was 0.9 (Driscoll, 1996e). Octadece-1-ene, applied as GULFTENE® 18, produced mean scores of 1.5 for erythema and 0.9 for oedema and irritant effects which were fully reversible by observation day 14 (Driscoll, 1996f). Octadec-1-ene, applied as SHOP alpha olefin C18, produced minimal inflammation at the treated site with a reported mean erythema score of 1.22 and oedema score of 0.14. All effects were fully reversible however dry and flaking skin was noted at the test site (Price, 1985).

Effects recorded in the aforementioned studies were generally slight to moderate and reversible; although occasional findings of moderate to severe irritation were present e.g. in one test using dec-1-ene and another on dodec-1-ene. However these latter findings were not replicated in a second study on dodec-1-ene, or in other guideline studies performed using closely-related linear alpha olefins. Based on a weight of evidence analysis, the available data indicate that C6 to C24-28 linear alpha olefins are mildly irritating to skin. However, the magnitude of the responses obtained was not such that it would trigger classification as “irritating to skin” (mean erythema or oedema scores ≥2 or ≥ 2.3, respectively, as described in EU Dangerous Substances Directive 67/548/EEC and CLP EU Regulation 1272/2008 (GHS aligned)).

 

There was no evidence of corrosive effects in any of these investigations.

Read-across eye irritation studies (Rinehart, 1967) from dec-1-ene and hexadec-1-ene were identified. Both studies showed that the respective test material was not irritating to the eyes of rabbits when administered at doses of 0.1 millilitres.

Justification for classification or non-classification

Linear alpha olefins do not meet the criteria for classification and labelling as skin irritants under EU Dangerous Substances Directive 67/548/EEC or CLP EU Regulation 1272/2008 (GHS aligned) based on evaluation of the overall mean erythema and oedema scores from skin irritation studies with these substances.

Hexacos-1-ene does not meet the criteria for classification as an eye irritant as defined by EU Dangerous Substances Directive 67/548/EEC or by CLP EU Regulation 1272/2008 (GHS aligned) based on the read across eye irritation studies with dec-1-ene and hexadec-1-ene which showed these substances not to be irritating to rabbit eyes.