IARC Monographs evaluation of the carcinogenicity of tris(chloropropyl) phosphate, butyraldehyde, and cumyl hydroperoxide

The results of the recent IARC Monographs evaluation of three chemicals – tris(chloropropyl) phosphate (TCPP), butyraldehyde, and cumyl hydroperoxide – have now been published in The Lancet Oncology. The summary article presents the conclusions of IARC Monographs Meeting 141.

All three chemicals were accorded high priority by the Advisory Group to Recommend Priorities for the IARC Monographs during 2025–2029, and each was evaluated by the IARC Monographs programme for the first time.

All three are chemicals with a high production volume and wide-ranging uses in industry. Butyraldehyde and cumyl hydroperoxide are used in the production of chemical intermediates, and TCPP is a flame retardant in polyurethane foams.

TCPP was classified as probably carcinogenic to humans (Group 2A) on the basis of the combination of sufficient evidence for cancer in experimental animals and strong mechanistic evidence in human primary cells. The Working Group classified butyraldehyde as possibly carcinogenic to humans (Group 2B) in two ways: (i) sufficient evidence for cancer in experimental animals; and (ii) strong mechanistic evidence in experimental systems. Cumyl hydroperoxide was classified in Group 2B on the basis of strong mechanistic evidence in human primary cells and experimental systems. For all three chemicals, the evidence regarding cancer in humans was inadequate.

The full scientific assessment will be published as Volume 141 of the IARC Monographs.

Lachenmeier DW, Arrandale VH, DeMarini DM, Ruksha T, Abdallah MA, Bettini G, et al.
Carcinogenicity of tris(chloropropyl) phosphate, butyraldehyde, and cumyl hydroperoxide
Lancet Oncol. Published online 27 March 2026;
https://doi.org/10.1016/S1470-2045(26)00168-3

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