Fatty acids, C16-18 and C18-unsatd., branched and linear

Endpoint summary

Description of key information

Based on read-across from a structurally related substance within a category approach, fatty acids, C16-C18 and C18 unsaturated, branched and linear are not irritating to the skin and not irritating to the eyes.

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

Justification for grouping of substances and read-across

In accordance with the specifications listed in Regulation (EC) No. 1907/2006 Annex XI, 1.5 Grouping of substances and read across, the similarity of category members has been shown to be justified based on the scope of variability and overlapping of composition, representative molecular structure, physico-chemical properties, tox-, ecotoxicological profiles and supporting Information by various validated QSAR methods. This information is given in further detail within the category justification for the grouping of chemicals and read-across (see IUCLID Section 13) for the dimerised fatty acids and its derivatives, and once more within the endpoint summary and discussion for Toxicokinetics.

For assessment of human health hazards of the category members, trends and similarities in toxicokinetic behaviour are most relevant. In particular, the molecular weight-dependent decrease in oral and dermal absorption and common metabolic pathways, which are explained by trends in molecular structure and common functional groups (monomers, dimers and trimers of similar long-chain fatty acids). This justifies the assumption that the toxicological profile of all category members is similar and effects or the lack of effects observed in toxicological studies of one ore more substances can also be expected and explained for the other substances in the category.

Therefore, in accordance with Annex XI, Item 1.5, of Regulation (EC) No 1907/2006, in order to avoid the need to test every substance for every endpoint, the category concept is applied for the assessment of human health hazards. Thus where applicable, human health effects are predicted from adequate and reliable data for reference substance(s) within the group by interpolation to other substances in the group (read-across approach).

All the available information from the substances within the category is taken into account for each endpoint to be assessed. Key studies are selected for assessment of the test substance and for read-across as to fulfil the requirements laid down in Annex XI, Item 1.5, of Regulation (EC) No 1907/2006, i.e. in all cases the results are adequate for the purpose of classification and labelling and/or risk assessment; have adequate and reliable coverage of the key parameters addressed in the corresponding test method referred to in Article 13(3); cover an exposure duration comparable to or longer than the corresponding test method referred to in Article 13(3) if exposure duration is a relevant parameter; and adequate and reliable documentation of the applied method is provided.

 

Discussion

Skin

There are no data available on the skin irritating potential of fatty acids, C16-C18 and C18 unsaturated, branched and linear. Therefore, assessment of the skin irritating properties was based on read-across from a structurally related substance within a category approach.

The skin irritating potential of isooctadecanoic acid (CAS No. 30399-84-9) was assessed in a study conducted according to OECD Guideline 404 and in compliance with GLP. A volume of 0.5 mL of the test material was applied undiluted to the shaved skin of 3 New Zealand White rabbits for 4 hours under semiocclusive conditions. Slight reactional dryness together with decrease in skin suppleness was observed. Clear irritative phenomena were observed. They remained during 24 hours without any changes, and then decrease regularly. On day 6, not any irritation was seen, but slight changes in skin structure persisted until day 10. The mean erythema and edema scores over 24, 48 and 72 h for each individual animal were 1.3/1.3/1.0 and 0.7/0.7/0.7, respectively. Erythema was fully reversible within 6 days, while edema was fully reversible within 72 h (Saboureau, 1989).

Fatty acids, C16-C18 and C18-unsaturated, branched and linear are derived from tall oil fatty acids. These as well as some pure C16-C18 fatty acids have been assessed for their safety when used as cosmetic ingredients, hence in contact with skin. On the basis of the evaluated data on acute toxicity in animals as well as skin irritation in both animals and humans, it was concluded that these substances are safe in present practices of use and concentration in cosmetics (CIR, 1987, 1989).

Taken together, the available information on structurally related substances (both included and not included in the chemical category) indicates that fatty acids, C16-C18 and C18 unsaturated, branched and linear are not likely to induce irritation in contact with the skin.

 

Eye

There are no data available on the eye irritating potential of fatty acids, C16-C18 and C18 unsaturated, branched and linear. Therefore, assessment of eye irritating properties was based on read-across from a structurally related substance within a category approach.

The eye irritating potential of the isooctadecanoic acid (CAS No. 30399-84-9) was investigated in a study conducted according to OECD Guideline 405 and in compliance with GLP. The test material (0.1 mL) was instilled into one eye of each of 3 New Zealand White rabbits, and the animals were observed at intervals for up to 72 h. A slight enanthema together with slight chemosis was observed in all 3 animals at the 1 hour reading. Enanthema remained during 48 hours in one animal and only 24 hours in the other two. Not any lesion of iris or cornea was recorded. The mean cornea and chemosis scores over 24, 48 and 72 h for all animals were both 0.0 (Boue-Grabot, 1989).

In eye irritation studies, some pure C16-C18 fatty acids (both undiluted and at concentrations between 1 and 19.4% in cosmetic product formulations) induced no or only minimal irritation after single or repeated (daily, 14-day) instillations into the eyes of rabbits. Irritation was primarily observed as very slight conjunctival erythema (CIR, 1987).

Taken together, the available information on structurally related substances (both included and not included in the chemical category) indicates that fatty acids, C16-C18 and C18 unsaturated, branched and linear are not likely to induce irritation in contact with the eyes.

Justification for classification or non-classification

Based on read-across from a structurally related substance within a category approach, the available information on the skin and eye irritating potential of fatty acids, C16-C18 and C18 unsaturated, branched and linear is conclusive but not sufficient for classification.