The following article features coverage from the American Association for Cancer Research (AACR) 2019 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Results from a molecular substudy of a cohort of men enrolled in the prospective Agricultural Health Study showed specific changes in hematologic parameters in individuals exposed to the pesticide permethrin. The findings from this study were presented at the American Association for Cancer Research (AACR) Annual Meeting 2019. 

Although results from the Agricultural Health Study, a prospective, observational study of cancer and other health outcomes in a cohort of licensed pesticide applicators from Iowa and North Carolina ( Identifier: NCT00352924), demonstrated an increased risk of developing multiple myeloma for individuals with a high lifetime exposure to permethrin, questions remain regarding the mechanisms of action through which permethrin exposure may increase multiple myeloma risk.

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For 33 individuals enrolled in the molecular substudy of the Agricultural Health Study, serial blood samples were collected each day after permethrin use, during the pesticide application off-season, and at a visit approximately 3 weeks following permethrin application (27 individuals for the latter sample collection). 

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Hematologic parameters were determined and their relationship to permethrin exposure was assessed using linear mixed models that were adjusted for the season of the blood draw; patient age, body mass index, and information about any recent colds/infections; and use of other pesticides. 

Statistically significant changes (P <.05) were observed in the following hematologic parameters between blood samples collected the day after permethrin use and samples collected during the off-season: increases in the adjusted mean immature granulocyte count, mean corpuscular volume, and red blood cell distribution width; and decreases in red blood cell count and hemoglobin. In addition, decreases in red blood cell count and hemoglobin and increases in red blood cell distribution width were shown to persist 3 weeks following exposure to permethrin. 

“Given the widespread use of permethrin in both residential and commercial settings, our findings may have public health implications beyond occupationally exposed pesticide applicators,” the study authors concluded. 

Read more of Cancer Therapy Advisor‘s coverage of AACR 2019 meeting by visiting the conference page.


  1. Shearer J, Beane Freeman L, Liu D, et al. A longitudinal investigation of hematologic perturbations among permethrin-exposed pesticide applicators in the Biomarkers of Exposure and Effect in Agriculture Study. Presented at: American Association for Cancer Research (AACR) Annual Meeting 2019; March 29–April 3, 2019; Atlanta, GA. Abstract 610/24.