Crosignani1 and Cogliano2 present opposing views about how to designate cancers in humans caused by chemicals or exposure situations. Straightforwardly, should one associate and spotlight all organ and tissue sites discovered in epidemiological studies that are considered related to the agent in question?1 Or should one only emphasise those exposures and causative cancer sites that are considered “confirmed”, for example, the International Agency for Research on Cancer (IARC) designation of “sufficient evidence of carcinogenicity”?2 Their debate1 2 centred largely on formaldehyde. In 2006, the IARC designated formaldehyde as Category 1 “carcinogenic to humans”3 citing only nasopharyngeal cancer as presenting confirmed evidence of carcinogenicity in relation to formaldehyde exposure.

With regard to formaldehyde, the …