Cancer incidence among pesticide applicators exposed to chlorpyrifos in the Agricultural Health Study.
BACKGROUND
Chlorpyrifos is one of the most widely used insecticides in the United States. We evaluated the incidence of cancer among pesticide applicators exposed to chlorpyrifos in the Agricultural Health Study, a prospective cohort study of licensed pesticide applicators in Iowa and North Carolina.


METHODS
A total of 54,383 pesticide applicators were included in this analysis. Detailed information on pesticide exposure and lifestyle factors was obtained from self-administered questionnaires completed at the time of enrollment (December 1993-December 1997). Poisson regression analysis was used to evaluate the association between chlorpyrifos exposure and cancer incidence after adjustment for potential confounders. All statistical tests were two-sided.


RESULTS
A total of 2070 incident malignant neoplasms were diagnosed through 2001. The rate ratio for all cancers combined among chlorpyrifos-exposed applicators compared with nonexposed applicators was 0.97 (95% confidence interval = 0.87 to 1.08). For most cancers analyzed, there was no evidence of an exposure-response relationship. However, the incidence of lung cancer was statistically significantly associated with both chlorpyrifos lifetime exposure-days (P(trend) = .002) and chlorpyrifos intensity-weighted exposure-days (P(trend) = .036). After adjustment for other pesticide exposures and demographic factors, individuals in the highest quartile of chlorpyrifos lifetime exposure-days (>56 days) had a relative risk of lung cancer 2.18 (95% confidence interval = 1.31 to 3.64) times that of those with no chlorpyrifos exposure.


CONCLUSIONS
Our findings suggest an association between chlorpyrifos use and incidence of lung cancer that deserves further evaluation.
Lee
Won Jin
WJ
Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Department of Health and Human Services, Rockville, MD 20852, USA.
Blair
Aaron
A
Hoppin
Jane A
JA
Lubin
Jay H
JH
Rusiecki
Jennifer A
JA
Sandler
Dale P
DP
Dosemeci
Mustafa
M
Alavanja
Michael C R
MC
D000328:Adult; D000382:Agricultural Workers' Diseases / Q000139:chemically induced* / Q000453:epidemiology*; D004390:Chlorpyrifos / Q000009:adverse effects*; D016001:Confidence Intervals; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D015994:Incidence; D007306:Insecticides / Q000009:adverse effects*; D007484:Iowa / Q000453:epidemiology; D008175:Lung Neoplasms / Q000139:chemically induced* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D009657:North Carolina / Q000453:epidemiology; D016273:Occupational Exposure / Q000009:adverse effects*; D016017:Odds Ratio; D016012:Poisson Distribution; D011446:Prospective Studies; D012107:Research Design; D011795:Surveys and Questionnaires
D007306:Insecticides; D004390:Chlorpyrifos