A new study of pesticide applicators has found that exposure to the pesticide chlorpyrifos may be associated with an increased incidence of lung cancer but concludes that more studies are needed.
About 8 to 10 million pounds of the insecticide chlorpyrifos were used in the U.S. agricultural sector in 1999. The chemical is found in approximately 800 products, which are used for a variety of purposes, including pest control of food crops, indoor pest control, and pet collars. Chlorpyrifos was widely used in U.S. households until 2000, when the Environmental Protection Agency phased out or limited some residential uses. Although there was little previous epidemiologic evidence of an association between exposure to chlorpyrifos and human cancer, human and animal studies have provided evidence that the chemical may be able to damage DNA.
To evaluate the incidence of cancer among pesticide workers exposed to chlorpyrifos, Michael C. R. Alavanja, Dr.P.H., of the National Cancer Institute, and colleagues analyzed data from the Agricultural Health Study, a prospective cohort study of more than 54,000 pesticide applicators from Iowa and North Carolina. For all cancers combined and for most cancers analyzed, they found no evidence of a relationship with exposure to chlorpyrifos. However, increased chlorpyrifos exposure was associated with an increased incidence of lung cancer. Individuals in the highest quartile of lifetime exposure-days had more than twice the risk of lung cancer compared with those with no chlorpyrifos exposure. The authors note that this result was not anticipated and that the lung cancer association should be interpreted cautiously until it is confirmed in future follow-ups of the AHS cohort and other studies.
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Journal of the National Cancer Institute