Incidence of lip cancer in the male Norwegian agricultural population

Objective: To explore lip cancer (LC) associations with work environmental exposures in a record-linkage study of Norwegian farmers. We hypothesize immunosuppressive substances (e.g. mycotoxins, pesticides) to influence LC incidence. Methods: A cohort of 131,243 male Norwegian farmers born 1925-1971 was established by cross-linkage of national registers and followed up through 1999 for incident LC, (ICD-7 site 140) in the Cancer Registry of Norway. Farm production data from agricultural censuses 1969-1979 and meteorological data on solar radiation and fungal forecasts (events of wet and temperate conditions known to favour fungal growth and mycotoxin formation) served as exposure proxies. Adjusted rate ratios (RR) and 95% confidence intervals (CI) were estimated using Poisson regression. Results: We identified 108 LC cases (rate 4.4 per 100,000 person-years). We found LC to be moderately associated with horses on the farm (RR = 1.6, CI = 1.0-2.4), construction work employment (RR = 1.7, CI = 1.1-2.6), pesticide use (RR = 0.7, CI = 0.4-1.0), grain production (RR = 1.3, CI = 0.9-2.1) and increasing levels of fungal forecasts (RR = 1.6, CI = 0.92.8 in the highest two quartiles). Conclusion: Moderate associations of LC with grain production and fungal forecasts and the negative association with pesticide could possibly be explained by exposure to immunosuppressive mycotoxins. Some of the associations observed could be explained by solar exposure.