Multiple myeloma risk and agricultural exposures

Background: Farming occupations and exposure to pesticides have been proposed to increase risk of multiple myeloma (MM). We analyzed risk associated with exposure to specific pesticides and contact with breeding animals using the occupational data base of the multicentre European EPILYMPH case-control study. Methods: The EPILYMPH data base includes 277 MM cases; the whole set of 2434 controls was used in the analysis. Information on contact with breeding animals and exposure to specific pesticide groups was obtained through personal interview by a detailed questionnaire and specific job modules. Local agronomists and occupational experts assessed likelihood, frequency and intensity of specific exposures. The Odds ratio and its 95% confidence intervals (OR, 95% CI) were calculated with unconditional logistic regression analysis adjusting for age (+/- 5 years), gender, and centre. Results. Ever exposure to any pesticide was not associated with an increase in risk of MM (OR = 1.4, 95% CI 0.8 - 2.5). A modest 23% excess risk (95% CI 0.8 – 2.0) was associated with ever exposure to organic pesticides The number of cases exposed to any individual group of pesticide was too low to test the association. Ever contact with breeding animals also did not show an association with MM risk (OR = 1.1, 95% CI 0.8 – 1.6). After reciprocal adjustment, ever exposure to pesticides showed a borderline significant excess risk (OR = 1.5, 95% CI 1.0 – 2.2). Risk associated with ever exposure to pesticides was highest after adjusting for contact with sheep (OR= 2.0, 95% CI 1.2 – 3.3). Conclusion: In our study, the prevalence of exposed to pesticides was too low to disentangle the effects of specific groups of chemicals. The finding of an excess risk associated with ever exposure to any pesticides after adjusting for contact with breeding animals is of unclear interpretation.