Occupational pesticide use and relative leukocyte telomere length in the biomarkers of exposure and effect in agriculture study.

Previous epidemiological studies have reported increased risks of certain cancers in relation to pesticide exposures. Although the biologic mechanisms underlying these associations are not well understood, altered telomere length has been hypothesized to play a role. We examined associations between occupational use of specific pesticides and leukocyte telomere length in the Biomarkers of Exposure and Effect in Agriculture study, a molecular epidemiological investigation of pesticide applicators in Iowa and North Carolina. Relative telomere length (RTL) was measured using quantitative polymerase chain reaction in leukocytes from 1539 male pesticide applicators ≥50 years of age. We evaluated lifetime use of 47 pesticides in terms of self-reported ever use and intensity-weighted lifetime days (IWLDs), a metric integrating lifetime days of use and other factors influencing exposure. Multivariable linear regression was used to estimate percent difference in geometric mean RTL in relation to ever (vs. never) use, IWLDs of use, and timing of use [recent (last 12 months) and former vs. never use]. Mean RTL was significantly longer among ever users of the insecticides lindane (percent difference = 2.20%, 95%CI: 0.45%, 3.99%) and aldicarb (percent difference = 3.27%, 95%CI: 0.23%, 6.40%). Longer RTL was also associated with increasing IWLDs of lindane (highest quartile vs. never use: percent difference = 4.51%, 95%CI: -0.22%, 9.46%; p-trend = 0.048) and the insecticide diazinon (4.77%, 95%CI: 0.17%, 9.58%; p-trend = 0.055), and with recent use of the insecticide dichlorvos (vs. never use: 8.15%, 95%CI: 1.31%, 15.46%). Increasing IWLDs of the insecticide heptachlor and the herbicide 2,4,5-TP and recent use of the herbicide metolachlor were significantly associated with shorter RTL. Our findings provide novel evidence suggesting that use of certain pesticides is associated with altered leukocyte telomere length. Notably, diazinon and lindane have previously been associated with increased risks of lung and lymphoid malignancies, respectively, and longer leukocyte telomere length has been implicated in the development of these cancers.