Workers exposed to the pesticide chlorpyrifos may have an elevated risk of lung cancer, according to a report from US government researchers. Scientists at the National Cancer Institute found that among the more than 54,000 farmers and insecticide applicators they followed for six years, those with the highest chlorpyrifos exposure had twice the risk of developing lung cancer as those who did not work with the pesticide. A later paper from this study linked cancers to exposure to another pesticide, diazonon.

Won Jin Lee, Aaron Blair and others. Cancer incidence among pesticide applicators exposed to chlorpyrifos in the Agricultural Health Study, Journal of the National Cancer Institute, volume 96, pages 1781-1789, 2004 [abstract].