2,4-Dichlorophenoxyacetic acid and non-Hodgkin's lymphoma, gastric cancer, and prostate cancer: meta-analyses of the published literature

PURPOSE: Despite evidence from experimental studies indicating that the herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), is not carcinogenic, several epidemiology studies have evaluated links between 2,4-D and cancer. Some suggest that 2,4-D is associated with non-Hodgkin's lymphoma (NHL), gastric cancer, and prostate cancer, but results have been inconsistent. We conducted meta-analyses to evaluate the weight of epidemiology evidence for these cancers. METHODS: We identified articles from PubMed, Scopus, and TOXLINE databases and reference lists of review articles. We evaluated study quality and calculated summary risk estimates using random effects models. We conducted subgroup and sensitivity analyses when possible. RESULTS: We identified nine NHL, three gastric cancer, and two prostate cancer studies for inclusion in our meta-analyses. We found that 2,4-D was not associated with NHL (relative risk RR = 0.97, 95% confidence interval CI = 0.77-1.22, I(2) = 28.8%, Pheterogeneity = .19), and this result was generally robust to subgroup and sensitivity analyses. 2,4-D was not associated with gastric (RR = 1.14, 95% CI = 0.62-2.10, I(2) = 54.9%, Pheterogeneity = .11) or prostate cancer (RR = 1.32, 95% CI = 0.37-4.69, I(2) 87.0%, Pheterogeneity = .01). CONCLUSIONS: The epidemiology evidence does not support an association between 2,4-D and NHL, gastric cancer, or prostate cancer risk.