Occupational Pesticide Use and Risk of Non-Hodgkin Lymphoma

Abstract

Background. Evidence on the human health effects of pesticides is needed to inform risk assessment.Methods. We conducted a large study of the relationship between occupational pesticide use and risk of non-Hodgkin lymphoma (NHL, including chronic lymphocytic leukemia and multiple myeloma) by pooling data from nine case-control studies participating in the InterLymph Consortium, including 7909 cases and 8644 controls from North America, the European Union, and Australia. Pesticide use was coded using a combination of self-report and expert assessment, for pesticide active ingredients (e.g., DDT, diazinon, 2,4-D, glyphosate) and chemical groups (e.g., organophosphate (OP) insecticides, phenoxy herbicides). We estimated the association between each exposure and risk of NHL using logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CI), with adjustment for age, gender, race, socioeconomic status, study location, and any pesticide use – for NHL, and separately for NHL subtypes.Results. OP insecticides were associated with increased risk of NHL. In particular, there was 43% higher risk associated with diazinon use (vs. never, 95% CI: 1.02, 2.00) and the association was stronger with longer duration (e.g., highest tertile duration vs. never, OR=2.40, 95% CI: 1.20, 4.78). We found no association between all NHL and pyrethroid insecticides or DDT. The phenoxy herbicide, 2,4-D, was associated with increased risk of NHL, and risk was most elevated for use within 20 years of diagnosis (i.e., unlagged) (e.g., ever vs. never: unlagged, OR=1.56, 95% CI: 1.06, 2.28; lagged, OR=1.23, 95% CI: 0.96, 1.56). Glyphosate use was not associated with risk of all NHL, but there were statistically significant risk increases for some NHL subtypes, specifically follicular lymphoma and NOS/unknown pathology.Conclusions. Our consortium-based pooled study produced evidence on potential carcinogenicity of certain pesticides. These findings are important because farming occupation and pesticides are among few leads for environmental causes of NHL.