Crude Tall Oil (CTO) is obtained from the wood pulping industry. It is a dark brown viscous liquid extracted and processed from softwoods and hardwoods. CTO has a complex composition of fatty acids, resin acids, and neutrals.

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

The only available skin sensitisation study for CTO is a murine local lymph node assay, conducted in accordance with OECD Test Guideline 429 and in compliance with GLP (Weber, 2005). The stimulation indices of the test substance were 0.9, 2.6 and 3.9 for the low, medium and high dose groups, respectively. The positive control group gave a SI of 5.3, thus demonstrating the validity of the test. According to the OECD test guideline a positive result should be regarded if the SI is equal to or greater than 3, together with consideration of the dose-response. A concentration-dependent response was observed, therefore it was concluded by the authors that Crude Tall Oil is sensitising to the skin.

Migrated from Short description of key information:
CTO was found to be sensitising in a murine local lymph node assay (LLNA) carried out in accordance with OECD Test Guideline 429 and in compliance with GLP (Weber, 2005).

Justification for classification or non-classification

Several independent toxicologists have reviewed the available LLNA study with a view to whether Crude Tall Oil should be classified for skin and respiratory sensitisation based on these results. Their findings can be found in the following references: Mallett, A.K., (2006) A Regulatory Assessment of the Skin and Respiratory Sensitisation Potential of Crude Tall Oil. & Illing, P., (2005) Evaluation of Draft report 'Crude Tall Oil Skin Sensitisation Study (LLNA). The reviewers came to different conclusions regarding the need to classify, mainly due to the apparent weak skin sensitising potential of Crude Tall Oil. Illing (2005) concluded that since the criteria for classification do not differentiate between weak and moderate/strong sensitisers, Crude Tall Oil would probably require classification. However, this would be precautionary. Mallett (2006) noted that since most skin sensitisers are not respiratory sensitisers in humans, automatic classification of Crude Tall Oil as a respiratory sensitiser would be highly precautionary.

Crude Tall Oil is classified as a skin sensitiser on the basis of a reliable (reliability 1) murine local lymph node assay (LLNA) that was carried out in accordance with OECD Test Guideline 429 and in compliance with GLP. CTO is therefore classified Xi; R43 "May cause sensitisation by skin contact" according to the criteria of EU Directive 67/548/EEC and Skin Sensitiser Category 1 according to Regulation 1272/2008.