The International Agency for Research on Cancer (IARC) is part of the World Health Organization.
IARC’s mission is to coordinate and conduct research on the causes of human cancer, the mechanisms of carcinogenesis, and to develop scientific strategies for cancer control. The Agency is involved in both epidemiological and laboratory research and disseminates scientific information through publications, meetings, courses, and fellowships
Formaldehyde was considered by previous working groups in October 1981 (IARC,1982), March 1987 (IARC, 1987a) and October 1994 (IARC, 1995). Since that time, new data have become available, and these have been incorporated in the monograph and taken into consideration in the evaluation.There is sufficient evidence in humans for the carcinogenicity of formaldehyde.
There is sufficient evidence in experimental animals for the carcinogenicity of formaldehyde.
Overall evaluation: Formaldehyde is carcinogenic to humans (Group 1).

2004 IARC Formaldehyde Monographs volume 88.pdf