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Prostate Cancer Risk Associated With Ambient Pesticide Exposure in California's Central Valley

Cockburn, M

doi: 10.1097/01.ede.0000289025.04330.d2

University of Southern California, United States.


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Some pesticides, classified as endocrine-disrupting chemicals (EDCs), can affect normal hormone function. Variations in hormone levels affect prostate cancer risk, because normal growth of the prostate gland is dependent on a critical balance of androgen levels. We hypothesized that previous studies of prostate cancer and pesticide exposure that only considered occupational exposures occurring at time of diagnosis would underestimate the true relationship due to (1) random misclassification (inaccurate estimation of exposure) and (2) specifically underestimating exposure in cases only, resulting in a differential bias toward the null.

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Materials and Methods:

We conducted a pilot case-control study of pesticide exposure and prostate cancer using our GIS-based Residential Ambient Pesticide Exposure Software (GRAPES) tool to estimate lifetime and age-specific exposures to a variety of pesticides and herbicides using residential history information, the California Pesticide Use Registry (PUR), and land-use information.

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Relative risk estimates were different when considering only diagnosis year exposures compared with lifetime exposures. However, these did not always result in a bias toward the null: the effect was pesticide-specific, presumably as a result of the variation in application of pesticides over time. There seems to be an increased risk of prostate cancer associated with exposure to methyl bromide and captan, but not to simazine. These results agree with studies of occupational exposure to pesticides where exposure levels far exceed those to be expected in the residential environment.

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Ambient exposure to pesticides seems to increase risk of prostate cancer. The impact of exogenous hormone exposure on prostate cancer might be substantial. More research is required to determine what mechanisms cause pesticides to increase risk of prostate cancers—although these are presumably related to the hormone-mimicking effects of some pesticides, the exact mechanism, and therefore a means of prevention of prostate cancer, remains unknown, but is a promising avenue for targeted research.

© 2007 Lippincott Williams & Wilkins, Inc.