Formaldehyde and cancers of the pharynx, sinus and nasal cavity: I. Occupational exposures

A population-based case-control study was undertaken in 13 counties of western Washington to determine if occupational formaldehyde exposure was related to cancer of the oro- and hypopharynx (OHPC, N = 205), nasopharynx (NPC, N = 27) or sinus and nasal cavity (SNC, N = 53). Controls were selected by random digit dialing (N = 552). A telephone interview inquired about lifetime occupational history as well as a number of potential confounding factors, including smoking and drinking. Approximately half (N = 143) of the case interviews were with next-of-kin. Occupational formaldehyde exposures were assessed by application of job-exposure matrix developed for this study which classified unique job codes into 4 categories based on judgement of likelihood and intensity of formaldehyde exposure. Exposure scores were calculated by weighing the number of years in a formaldehyde-associated job by the assigned exposure level. The effects assuming a 15-year induction period were also investigated. Logistic regression was used to estimate exposure odds ratios (OR) while taking into account multiple risk factors for each site. No significant associations were found between occupational formaldehyde exposure and any of the cancer sites under study. However, relative risk estimates associated with the highest exposure score categories were elevated for OHPC (OR = 1.3, 95% Confidence Interval = 0.6-3.1) and NPC (OR = 2.1, 95% CI = 0.4-10.0) when an induction period was accounted for. When only live interviews were considered, the odds ratios for OHPC and NPC increased to 1.7 and 3.1 respectively. Several limitations in the study tend to conservatively bias the results and must be taken into account in its interpretation.