On March 27, 2026, the International Agency for Research on Cancer (IARC) announced the publication in The Lancet Oncology of the results of its assessment of the carcinogenicity of Butyraldehyde, a fragrance ingredient.
This assessment was finalized by a group of 12 scientists from nine countries during a meeting held at the Agency’s headquarters in Lyon in March 2026.
It has now been published in The Lancet Oncology.
Butyraldehyde (CAS No.123-72-8, EC No.204-646-6, INCI: Butyraldehyde) is an ingredient listed in CosIng with the function: Perfuming.
It is not currently regulated by the European Cosmetics Regulation 1223/2009.
It is listed in Annex VI/605-006-00-2 of the European CLP Regulation 1272/2008 with the following classification:
• Flam. Liq. 2, H225 - Highly flammable liquid and vapor.
The IARC Working Group classified butyraldehyde as “possibly carcinogenic to humans” (Group 2B) based on two types of data:
• sufficient evidence for cancer in experimental animals,
• strong mechanistic evidence in experimental systems.
The full scientific assessment will be published as Volume 141 of the IARC Monographs.
Sources
• IARC Monographs evaluation of the carcinogenicity of tris(chloropropyl) phosphate, butyraldehyde, and cumyl hydroperoxide, IARC News, 27 March 2026
• Carcinogenicity of tris(chloropropyl) phosphate, butyraldehyde, and cumyl hydroperoxide, Lachenmeier D, Arrandale V, DeMarini D et al., The Lancet Oncology, 2026; 0
