Evaluates the carcinogenic risk to humans posed by occupational exposures to wood dust and formaldehyde. A number of occupational situations that involve exposure to wood dust also entail exposure to formaldehyde, as in plywood and particle board manufacture, during furniture and cabinet-making, and during parquet floor sanding and varnishing. The carcinogenic risks of wood dust are evaluated in the first monograph. The highest occupational exposures were noted to occur in wood furniture and cabinet manufacture, especially during machine sanding and similar operations, in the finishing departments of plywood and particle-board mills, and in the workroom air of sawmills and planer mills near chippers, saws, and planers. Citing findings from several recent well-designed case-control studies, the monograph concludes that occupational exposure to wood dust is causally related to adenocarcinoma of the nasal cavities and paranasal sinuses. The evaluation further concluded that the excess risk of cancer is attributable to wood dust per se, rather than to other exposures in the workplace. Wood dust was classified as carcinogenic to humans. Cancer risk associated with occupational exposure to formaldehyde is assessed in the second monograph. The assessment draws on findings from several cohort and case-control investigations of the relationship between exposure to formaldehyde and cancer of the oral cavity, pharynx, and respiratory tract. Citing inconsistencies in the reported results, the monograph concludes that these epidemiological studies can do no more than suggest a causal role of occupational exposure to formaldehyde in carcinoma of the nasal cavities and paranasal sinuses. The review found no evidence of excess risk for oropharyngeal, laryngeal or lung cancer among exposed workers. Several studies in which formaldehyde was administered to rats by inhalation showed evidence of carcinogenicity. Similar studies in hamsters showed no evidence of carcinogenicity, and studies in mice either showed no effect or were inadequate for evaluation. In rats administered formaldehyde in drinking-water, increased incidences were seen of forestomach papillomas in one study and of leukaemias and gastrointestinal tract tumours in another; two other studies gave negative results. Formaldehyde was classified as probably carcinogenic to humans.