Farming, pesticide use and hairy-cell leukemia

Objectives This paper analyzes the role of farming and pesticide exposures in the occurrence of hairy-cell leukemia (HCL). Methods The study included 226 men with HCL and 425 matched hospital referents. Pesticide exposure was assessed by expert review of detailed interview data on occupational histories and agricultural activities and exposures. Results Altogether, 77 cases and 116 referents had farmed for at least six months, giving an odds ratio (OR) of 1.5 [95% confidence interval (95% CI) 1.0--2.2]. Forage growing was reported by 20.8% of the cases and 11.1% of the referents and was associated with HCL (OR 2.8, 95% CI 1.6--4.9), even among farmers who had never handled pesticides (OR 3.4, 95% CI 1.0--11.0). A significant association was found between HCL and pesticide use, the overall odds ratios for insecticide, fungicide, and herbicide use ranging from 1.5 to 2.4. Organophosphorus insecticides, were the only agrochemicals with a positive association with HCL after other pesticide exposures, smoking and forage growing were accounted for. A clear-cut negative interaction was found between smoking and exposure to organophosphorus insecticides. A multivariate analysis yielded odds ratio estimates of 2.8 (95% CI 1.4--5.6) for exposure to forage and 7.5 (95% CI 0.9--61.5) for nonsmokers exposed to organophosphorus insecticides. Conclusions The present study argues for a role of organophosphorus insecticides in HCL among nonsmoking farmers and shows an unexpected association with forage growing. No evidence of an association with phenoxyacetic acids, triazines, or organochlorine insecticides was found.