Insecticide use and risk of non-Hodgkin lymphoma subtypes: a subset meta-analysis of the North American Pooled Project

Insecticide use has been linked to increased risk of Non-Hodgkin lymphoma (NHL), however findings of epidemiologic studies have been inconsistent, particularly for NHL subtypes. We analyzed 1690 NHL cases and 5131 controls in the North American Pooled Project (NAPP) to investigate self-reported insecticide use and risk of NHL overall and by subtypes: follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), and small lymphocytic lymphoma (SLL). Odds ratios (OR) and 95% confidence intervals for each insecticide were estimated using logistic regression. Subtype-specific associations were evaluated using ASSET (Association analysis for SubSETs). Increased risks of multiple NHL subtypes were observed for lindane (OR=1.60, 1.20-2.10: FL, DLCBL, SLL), chlordane (OR=1.59, 1.17-2.16: FL, SLL), and DDT (OR=1.36, 1.06-1.73: DLBCL, SLL). Positive trends were observed, within the subsets with identified associations, for increasing categories of exposure duration for lindane (p_trend =1.7×10^-4 ), chlordane (p_trend =1.0×10^-3 ), and DDT (p_trend =4.2×10^-3 ), however the exposure-response relationship was non-linear. Ever use of pyrethrum was associated with an increased risk of FL (OR=3.65, 1.45-9.15), and the relationship with duration of use appeared monotonic (OR for >10 years: OR=5.38, 1.75-16.53; p_trend =3.6×10^-3 ). Our analysis identified several novel associations between insecticide use and specific NHL subtypes, suggesting possible etiologic heterogeneity in the context of pesticide exposure. This article is protected by copyright. All rights reserved.

Keywords: Non-Hodgkin lymphoma (NHL); insecticides; meta-analysis; organochlorines; pesticides.