Ag Study Offers Data on Pesticides, Cancer

“Melanomas are the most dangerous kind of skin cancer and one you need to be able to detect early, because if left untreated, they can spread and be fatal.”

By Helen Murphy (NURSE MURF)

The Agriculture Health Study is the most in-depth study ever conducted on the health of pesticide applicators. Enrolled between 1993 and 1997 in Iowa and North Carolina, 57,284 pesticide applicators and 32,333 spouses of applicators are being followed for various health outcomes.

Detailed information is collected on pesticide use, other agricultural exposures, work practices, diet, exercise, alcohol consumption, tobacco use, medical conditions, family history of cancer and other occupations. A special focus is on cancer, which is reported and linked to the study participants through cancer registries as they occur after enrollment.

To date, the overall occurrence of cancers among applicators and spouses is less than among other people of the same age, sex and race in those two states. Also, cancers previously found associated to pesticides in other studies (Hodgkin’s disease, non-Hodgkin’s lymphoma, multiple myeloma, leukemia and brain cancer) were not increased.

However, compared to the general population, a few cancer types occurred more frequently among the applicators and their spouses. Some cases were associated with high use of specific chemicals. While still requiring more study, slightly more-than-expected ovarian cancer among female applicators and melanoma among applicators’ wives were found.

Further study

Slightly higher rates (14%) of prostate cancer occurred with applicators of restricted-use pesticides. Those using methyl bromide had a higher risk for prostate cancer; the highest users showing an almost three-and-a-half times more risk for prostate cancer. The other chemicals linked to prostate cancer (butylate, chlorpyrifos, coumaphos, fonofos, permethrin for animal use and phorate) occurred only in applicators whose brother or father had prostate cancer. This suggests that these chemicals may interact with prostate cancer genes making the individual more susceptible.

Farmers smoke half as much as the general population, and likewise have an overall lower rate of lung cancer by 2.27 times. But greater lung cancer risk was associated to frequent use of two herbicides — metolchlor and pentimethalin — and two insecticides — chlorpyrifos and diazinon. This was independent of smoking, gender, age and total days of other pesticide use. However before a firm cause-and-effect relationship can be established, more study is needed to confi rm this first-ever seen association.

Caution heeded

Another issue under study is the link between pesticides, which act like the body’s own estrogen, and breast cancer. Fewer women in the study developed breast cancer than the general population. Could women who live and work on the farm, or apply pesticides, have healthier lifestyles, more physical activity or more vitamin D from being in the sun?

Researchers are looking into these issues. On the other hand, a modest increase in risk was seen in the wives of applicators of a few chemicals including 2,4,5-TP and to a lesser extent dieldrin, captan and 2,4,5-T. Of these, only captan is available for use in the U.S.

While risks do not reach the magnitude of carcinogens like tobacco (smoking causes a twentyfold increase in cancer), this information suggests that erring on the side of caution by safely handling and judiciously using pesticides is still prudent.

Murphy, director of Outreach at the Pacific Northwest Agricultural Safety and Health Center at the University of Washington, may be reached by phone at 206-616-5906 or by e-mail at

For more on the study, go online to

Publication #: Western Farmer Stockman, July 2007

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