Fatty acids, C18-unsatd.

Endpoint summary

Description of key information

Irritation / corrosion:
- skin: not irritating (Analogy CAS 67701-08-0, CAS 57-11-4);
- eye: not irritating (Analogy CAS 67701-08-0, CAS 57-11-4);

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

Skin

Due to lack of reliable data with fatty acids C18-unsatd. on skin irritation, studies with the analogues fatty acids C16-18 and C18-unsatd. are used for the hazard assessment. Since fatty acids C18-unsatd. and fatty acids C16-18 and C18-unsatd. have similar compositions and belong to the same category based on similar structural and toxicological properties, this approach can be regarded as scientifically justified. Thus, read-across is performed based on a category approach (for details refer to IUCLID chapter 13).

 

Skin irritation by fatty acids C16-18 and C18-unsatd. was evaluated in a study performed according to GLP and OECD guideline 404 and EU method B.4. Four Kleinrussen rabbits received a dermal application of o.5 g fatty acids C16-C18 and C18 unsat. to the shaved skin of the back under occlusion for 4 hours. The resulting mean scores after 24 – 72 hours for edema and erythema were 1.8 and 1.0, respectively. While the erythema reactions were reversible in 10 days, the observed edema reactions diapered within 7 days. Based on this finding, fatty acids C16-C18 and C18 unsat. can be regarded as not irritant to skin (Kästner, 1988).

In addition to studies with animals two studies with human volunteers on skin irritation byfatty acids C16-18 and C18-unsatd.were available for assessment. In the first study, 10µL of the substance at concentration of 50 % was applied to the back of 20 subjects for 24 hours using a Large Finn Chamber on Scanpor (Herma). No reactions were found when the application sites were evaluated 1, 6, 24, 48, 72 and 14 hours later, respectively (Matthies, 1988). In the second study with volunteers, the test substance at a concentration of 80% was applied to the forearm of 10 volunteers, which was repeated every 30 seconds for 30 minutes. The reactions were scored 1 and 24 hours after the last application until disappearance of the symptoms. As result, 1/10 subjects showed erythema with the lowest score after 30 min, which disappeared after 30-35 min. The other subjects did not show any symptoms (Matthies, 1988).

Together the results of the human and animal studies show thatfatty acids C16-C18 and C18 unsat. are not irritating to skin.

 

Additionally a study with one of the constituents of with fatty acids C18-unsatd., stearic acid, is also used for the hazard assessment.

Skin irritation by stearic acid was evaluated in a study performed in accordance with federal guidelines (International Bio-Research, 1974). 0.5 mL of stearic acid was applied to the abraded skin of 6 New Zealand White rabbits under occlusion for 24 hours.at 24 and 72 hours after application revealed no signs of irritation. Although a longer application under occlusion than suggested according to actual guidelines, the resulting scores are 0, both for erythema and edema, respectively. Based on this, stearic acid can be regarded as not irritating to skin.

 

Based on the available data on skin irritation by the constituent stearic acid and the analogue acids C16-18 and C18-unsatd., fatty acids C18-unsatd. can be regarded as not irritating to skin since the substances belong to the same category based on similar structural and toxicological properties.

 

Eye:

Due to lack of reliable data with fatty acids C18-unsatd. on eye irritation, studies with the analogues fatty acids C16-18 and C18-unsatd. are used for the hazard assessment. Since fatty acids C18-unsatd. and fatty acids C16-18 and C18-unsatd. have similar compositions and belong to the same category based on similar structural and toxicological properties, this approach can be regarded as scientifically justified. Thus, read-across is performed based on a category approach (for details refer to IUCLID chapter 13).

 

Irritation to eyes was analyzed in a study performed according to GLP and OECD guideline 405 and EU method B.5. 0.1 g of fatty acids C16-C18 and C18 unsat. was instilled into the right eyes of three Kleinrussen rabbits, while the left eyes served as controls. While no corneal or iris reactions were noted, only slight conjunctival effects were noted which were disappeared within at least 24 hours. The resulting mean scores after 24 – 72 hours for corneal opacity, iris, conjunctival erythema and chemosis were found to be all 0, respectively. Thus, fatty acids C16-C18 and C18 unsat. can be regarded as not irritating to eyes.

 

Additionally a study with one of the constituents of with fatty acids C18-unsatd., stearic acid, is also used for the hazard assessment.

In a published study performed according to national guidelines, stearic acid was instilled into the eyes of six rabbits (Briggs, et al., 1976). Mild conjunctival erythema was found in 2 animals at 24 and 48 hours while all signs of irritation hat subsided completely in 72 hours. Thus, a mean score of 0.2 for conjunctival erythema could be calculated. Based on the results, stearic acid can be regarded as not irritating to eyes

Based on the available data on skin irritation by the constituent stearic acid and the analogue acids C16-18 and C18-unsatd., fatty acids C18-unsatd. can be regarded as not irritating to eyes since the substances belong to the same category based on similar structural and toxicological properties.

Justification for classification or non-classification

 The substance may contain few of lauric acid (C12), which is classified as R41 and decanoic acid (C10), which is classified as R36/38. The specific concentration limit for the lauric acid is established as 73.6% based on a reliable experimental data. According to DPD (1999/45/EC) or CLP (1272/2008/EC) classification criteria for irritation/corrosion, fatty acids C18-unsatd. do not fulfill the criteria for classification and thus a non-classification is warranted for this endpoint, as the concentration of C12 is lower than 73.6% and C10 < 20%.