Methyl bromide ups prostate risk.

While many men know more about prostate cancer from firsthand experience than they want to, scientists know less than they would like. They do know, however, that African Americans and men with a family history of the disease are much more likely to develop this second-leading cause of cancer death in the United States. Smoking and eating a high-fat diet also appear to confer greater risk, and studies have linked the disease to exposure to pesticides and other farm chemicals. Now, for the first time, research has linked one particular pesticide--methyl bromide--with prostate cancer.

The study was part of the Agricultural Health Study, which the National Cancer Institute, the NIEHS, and the Environmental Protection Agency began in 1994. The participants filled out questionnaires about their use of pesticides and protective equipment, pesticide application methods, crops grown, livestock raised, smoking, alcohol use, diet, medical history, and more. The researchers determined the incidence of cancer through state cancer registries.

Scientists led by Michael C.R. Alavanja, a senior investigator with the National Cancer Institute, analyzed the relationship between exposure to common agricultural pesticides and eventual development of prostate cancer in 55,332 initially healthy men who applied pesticides in Iowa and North Carolina. Over a period of 4 years, 566 of the men developed prostate cancer. Among the 45 pesticides evaluated, the only statistically significant exposure-response trend observed occurred with methyl bromide, the team reports in the 1 May 2003 American Journal of Epidemiology.

Methyl bromide is a broad-spectrum pesticide that the National Institute for Occupational Safety and Health lists as a potential occupational carcinogen, based on animal studies. It is currently being phased out in the United States and elsewhere because of its damaging effect on the Earth's ozone layer.

Men exposed to the pesticide had a 2-4 times greater risk of developing prostate cancer than men not exposed, and the greater their exposure levels, the greater their risk. Study participants had a 14% higher risk of developing prostate cancer than the general population. Nineteen percent of the study's prostate cancer patients had a family history of the disease, compared with almost 9% of men who didn't get sick. Six insecticides were linked to prostate cancer only in men with a family history, conferring a two-fold excess risk of prostate cancer.

According to David Savitz, chair of the department of epidemiology at the University of North Carolina School of Public Health in Chapel Hill, the study is a unique resource, because it ascertains exposure levels in great detail, has a large study population, and is prospective. The study is so unique, in fact, that it would be difficult to replicate its findings or to support them with historical data, he notes.

Alavanja and his colleagues are currently assessing the link between lung cancer and pesticide use, with plans to assess the neurotoxicity of the studied pesticides.