Phorate exposure and incidence of cancer in the agricultural health study.
BACKGROUND
We recently reported a link between use of the organophosphate pesticide phorate and risk of prostate cancer among applicators with a family history of prostate cancer in the Agricultural Health Study (AHS).


OBJECTIVE
This finding, together with findings of associations between other organophosphate pesticides and cancer more broadly, prompted us to examine phorate exposure and overall cancer incidence in the AHS. Adding 3 years of follow-up and using more detailed exposure information allowed us to see whether the prostate cancer finding held.


METHODS
The AHS is a prospective study of licensed restricted-use pesticide applicators from North Carolina and Iowa. To our knowledge, this is the largest examination of workers occupationally exposed to phorate. Pesticide exposure and other information was collected using two self-administered questionnaires completed from 1993 to 1997. Poisson regression was used to calculate rate ratios (RR) and 95% confidence intervals (CI), adjusting for potential confounders.


RESULTS
Phorate use was not related to the incidence of all cancers combined or to any individual cancer, although we had insufficient numbers to study non-Hodgkin lymphoma or leukemia, which have been linked to organophosphates in other studies. Although prostate cancer risk was not significantly related to phorate use overall or among those without a family history, the risk tended to increase among applicators with a family history of prostate cancer. The interaction RR was 1.53 (95% CI, 0.99-2.37).


CONCLUSIONS
The observed statistical interaction suggests a gene-environment interaction between family history and phorate exposure in the incidence of prostate cancer, but other explanations are also possible.
Mahajan
Rajeev
R
Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, USA.
Bonner
Matthew R
MR
Hoppin
Jane A
JA
Alavanja
Michael C R
MC
D000328:Adult; D000368:Aged; D000382:Agricultural Workers' Diseases / Q000453:epidemiology*; D000428:Alcohol Drinking / Q000453:epidemiology; D015331:Cohort Studies; D005500:Follow-Up Studies; D006801:Humans; D007306:Insecticides / Q000009:adverse effects* / Q000032:analysis*; D007484:Iowa / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009657:North Carolina / Q000453:epidemiology; D016273:Occupational Exposure / Q000009:adverse effects*; D010702:Phorate / Q000009:adverse effects* / Q000032:analysis*; D011471:Prostatic Neoplasms / Q000453:epidemiology*; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D003313:Zea mays
D007306:Insecticides; D010702:Phorate