Abstract 274: Occupational exposure to agricultural pesticides and CLL risk
Authors: Hallberg Emily J. , Achenbach Sara J. , Rabe Kari G. , Call Timothy G. , Allmer Cristine , Shanafelt Tait D. , Liebow Mark , Kay Neil E. , Cerhan James R. , Slager Susan L. 
Published: May 2015

Abstract
Background
Previous literature regarding the association between occupational exposure to agricultural pesticides and non-Hodgkin lymphoma (NHL) risk has been inconsistent, particularly when looking at specific lymphoma subtypes. Most recently, a large European case-control study showed an elevated risk of chronic lymphocytic leukemia (CLL) among those ever exposed to inorganic and organic pesticides with the strongest association among those exposed to organophosphates. However, when restricting the analysis to subjects with high confidence of exposure, these associations were attenuated (Cocco P., 2013). We used case-control data from the Mayo Clinic to evaluate whether there is an increased risk of CLL among individuals with known occupational exposure to agricultural pesticides.
Methods
We evaluated pesticide exposure and CLL risk in a clinic-based study of newly diagnosed CLL cases and frequency-matched controls enrolled at the Mayo Clinic from 2002-2012. 200 CLL cases and 474 controls returned a detailed farming and pesticide exposure questionnaire that was modeled after the Agricultural Health Study, where exposure was based on pesticide-specific application. Unconditional logistic regression, adjusted for age and sex, was used to estimate odds ratios (ORs) and 95% confidence intervals (CI). We evaluated the effect of each pesticide individually, by chemical class of pesticides, and by an aggregate of multiple pesticide exposure on CLL risk.
Results
Among those participants with detailed farming data, the mean age of CLL diagnosis was 66 years and 76% were male; for controls, the mean age at enrollment was 65 years and 66% were male. Risk of CLL was mildly elevated, but not significant, amongst those with application of any pesticide (OR 1.39; 95% C.I. 0.92-2.10). When broken down by chemical class, risk of CLL was also mildly elevated, but not significant, for application of organophosphates and carbamates (OR 1.21; 95% CI 0.84-1.73; OR 1.21; 95% 0.85-1.73, respectively). Organochlorines, phenoxy compounds, pyrethriods and triazines showed no evidence of an elevated risk, nor did we see evidence of a trend that CLL risk increases with number of pesticides applied.
Discussion
Our preliminary results provide inconclusive support for the role of pesticide exposure as a possible risk factor for CLL. However our sample size was small. Additional data will be incorporated, including confidence of exposure measures, as well as other modifying factors, to further evaluate these results.
Citation Format: Emily J. Hallberg, Sara J. Achenbach, Kari G. Rabe, Timothy G. Call, Cristine Allmer, Tait D. Shanafelt, Mark Liebow, Neil E. Kay, James R. Cerhan, Susan L. Slager. Occupational exposure to agricultural pesticides and CLL risk. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 274. doi:10.1158/1538-7445.AM2014-274