Fatty acids, C18-22

Endpoint summary

Description of key information

Skin irritation (Federal Guidelines): not irritating; CAS# 57-11-4, C18 (USFHSA, 1974)
Skin irritation (QSAR): not irritating; CAS# 112-85-6, C22 (Szymoszek, 2012)
Skin irritation (human, repeated occlusive patch test, 1M): not irritating CAS# 57-11-4, C18 (Stillman et al., 1975)
Eye irritation (Federal Guidelines): not irritating; CAS# 57-11-4, C18 (USFHSA, 1974)
Eye irritation (QSAR): not irritating; CAS# 112-85-6, C22 (Szymoszek, 2012)

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)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin

No data on skin irritation/corrosion are available for fatty acids, C18-22. Therefore, skin irritation effects are predicted from adequate and reliable data for source substances by read-across to the target substance within the group applying the group concept in accordance with Annex XI, Item 1.5, of Regulation (EC) No 1907/2006. Available studies with the main constituents C18 fatty acid (stearic acid) and C22 fatty acid (docosanoic acid) are used for assessment.

 

Skin irritation by stearic acid (CAS# 57-11-4) was evaluated in a study performed in accordance with US Federal Guidelines (USFHSA, 1974). 0.5 mL of stearic acid was applied to the abraded skin of 6 New Zealand White rabbits under occlusion for 24 h.at 24 and 72 h after application revealed no signs of irritation. The resulting scores were 0 for erythema and edema, respectively, although the exposure duration was under occlusive conditions and longer than suggested according to current the OECD Guideline. Based on the study result, stearic acid can be regarded as not irritating to skin.

In a study with humans, daily application of 28.4% stearic acid (w/v) under occlusive conditions did not cause irritation in any of the 10 subjects until the termination of the study on day 10 (Stillman et al., 1975).

 

In addition, a qualitative SAR method has been applied for docosanoic acid. By means of the OECD QSAR toolbox (v2.2) it can be determined whether inclusion rules (examination for the presence of structural alerts) and exclusion rules (on the basis of physico-chemical properties) are fulfilled for skin irritation/corrosion (Szymoszek, 2012). No alerts were detected for docosanoic acid and a skin irritation/corrosion classification (R34, R35, R38) can be excluded on the basis of log Kow, water solubility, melting point and vapour pressure based rules.

 

Based on the available data, stearic acid and docosanoic acid have no skin irritation potential.

Since stearic acid and docosanoic acid are main constituents of fatty acids, C18-22 and all substances belong to the same category based on structural and toxicological properties, the same result can be expected for fatty acids, C18-22. Thus, fatty acids, C18-22 are considered to be not irritating to skin.

 

Eye

No data on eye irritation is available for fatty acids, C18-22.Therefore, eye irritation effects are predicted from adequate and reliable data for source substances by read-across to the target substance within the group applying the group concept in accordance with Annex XI, Item 1.5, of Regulation (EC) No 1907/2006. Available studies with the main constituents C18 fatty acid (stearic acid) and C22 fatty acid (docosanoic acid) are used for the hazard assessment.

 

Eye irritation by stearic acid (CAS# 57-11-4) was examined in a non-GLP study according to US Federal Guidelines (USFHSA, 1974). 0.1 g stearic acid was applied into the eyes of six albino rabbits. The untreated left eye of each animal served as control. The eyes were examined at 24, 48 and 72 h and scored for corneal opacity, iris lesions, conjunctival redness, chemosis and discharge. No lesions were observed in any of the animals, thus the overall score for all irritation parameters was 0.

For docosanoic acid a qualitative SAR based on structural alerts and physico-chemical data was performed to make a prediction for its eye irritation potential by means of the OECD QSAR toolbox (v2.2) (Szymoszek, 2012). No structural alerts for eye irritation have been determined for docosanoic acid and classification as R34, R35, R36 and R41 could be excluded based on the log Kow, water solubility and melting point based rules.

 

Thus, stearic acid and docosanoic acid are not irritating to the eye based on the available animal and QSAR data.

Since stearic acid and docosanoic acid are main constituents of fatty acids, C18-22 and all substances belong to the same category based on structural and toxicological properties, the same result can be expected for fatty acids, C18-22. Thus, fatty acids, C18-22 are considered to be not irritating to the eye.

Justification for selection of skin irritation / corrosion endpoint:
Hazard assessment is conducted by means of read-across based on a category approach. All available studies are adequate and reliable based on the identified similarities in structure and intrinsic properties between source and target substances and overall quality assessment (refer to the endpoint discussion for further details).

Justification for selection of eye irritation endpoint:
Hazard assessment is conducted by means of read-across based on a category approach. All available studies are adequate and reliable based on the identified similarities in structure and intrinsic properties between source and target substances and overall quality assessment (refer to the endpoint discussion for further details).

Justification for classification or non-classification

Fatty acids, C18-22 do not contain any components, which are classified as irritanting/corrosive to the skin or as irritating or seriously damaging to the eye. Thus, fatty acids, C18-22 do not meet the criteria for classification according to Regulation (EC) 1272/2008 or Directive 67/548/EEC.