President's Cancer Panel Meeting: Environmental Factors in Cancer, Transcript of Proceedings, Indianapolis, in, Oc by National Cancer Institute - HTML preview

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Key Points

The AHS is a cohort of 57,310 licensed pesticide applicators (and over 30,000 of their

spouses) in North Carolina and Iowa. The initial enrollment questionnaire (given 1993 to

1997), recorded information on the ever use of 50 individual pesticides, including herbicides, insecticides, fungicides, and fumigants. The pesticide exposures were then ranked using an

intensity-rating algorithm that accounts for factors such as application method, mixing status, whether or not someone mixed the pesticides themselves, whether or not they repaired their

own equipment, and the use of protective clothing.

Farmers are typically healthier than the general population, with higher rates of physical activity and lower rates of tobacco and alcohol use. As a result, they have lower incidence

rates of lung, bladder, and colon cancer. However, farmers have a large number of unique

exposures including higher levels of pesticides, viruses and endotoxins from animals; engine

exhaust; biologically active dust; and other zoonotic microbes. This may explain the higher

incidence rates of leukemia, multiple myeloma, non-Hodgkin’s lymphoma, and lip, stomach,

brain, and prostate cancers among farmers.

Indianapolis, IN

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October 21, 2008

Data from the AHS show that 70 percent of farmers in North Carolina have held a job off of the farm; 40 percent of those held that job for more than 20 years. Solely relying on the term

“farmer” does not capture the broad spectrum of exposures these workers encounter.

Two types of analyses are used within the AHS to examine the links between use of specific pesticides and cancer—a nested case-control analysis and a cohort analysis. The nested case-control analysis compares people with a specific cancer and those without and looks for

differences in chemical exposures. The cohort analysis compares people who use a certain

chemical and those who do not and looks for differences in cancer risks. Such complementary

analyses provide the ability to statistically control for use of other pesticides and exposures.

There have been over 6,000 cases of incident cancer diagnosed within the AHS cohort.

Cancer incidence among farmers is approximately 15 percent lower in comparison to the

general population. However, spouses of pesticide applicators have elevated risks of prostate cancer, ovarian cancer, and melanoma. The AHS does not provide conclusive evidence that

any pesticide causes a specific cancer—it is the first evaluation of cancer risk in humans for many of the chemicals being studied.

Currently, the AHS is in the process of updating exposure information. Participants were

administered a telephone interview five years after the initial enrollment questionnaire was

given; that information is being incorporated into the analyses. The study is also linking to cancer registries, resulting in accrual of additional cases into the cohort. Using available

biologic materials, the interaction between specific genetic polymorphisms and exposure to

specific pesticides will also be studied.

A consortium of agricultural cohorts was created that includes over 1 million study

participants from around the world. This type of collaboration presents the opportunity to

facilitate agricultural research and study rare outcomes and exposures.

DR. SUZANNE FENTON:

THE MAMMARY GLAND: A TISSUE SENSITIVE TO ENVIRONMENTAL

EXPOSURES