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Pesticide Exposure, Family History Raise Risk of Prostate Cancer

Christensen, CH, EA Platz, G Adreotti, A Blair, JA Hoppin, S Koutros, CF Lynch, DP Sandler and MCR Alavanja. 2010. Coumaphos exposure and incident cancer among male participants in the Agricultural Health Study (AHS). Environmental Health Perspectives

Synopsis by Jonathan Chevrier, Ph.D.

A study of professional pesticide applicators suggests that exposure to the insecticide coumaphos may increase their risk of prostate cancer if they had a family history of the disease. 

Men are more prone to developing prostate cancer if they meet a dual criteria: exposure to an organophosphate pesticide and relatives who had the disease. The results of this large study confirm prior studies that found an association between the pesticide and cancer in men with a family history of the disease.

The insecticide coumaphos - part of a group of pesticides named organophosphates - is primarily used to control pests on beef and dairy cattle. Between 1990 and 1999, more than 70,000 pounds of coumaphos were used on 6 million livestock annually in the United States. Though unlikely, exposure to the general population may occur when eating food products from coumaphos-treated animals, such as meat or milk.

In this study, male pesticide applicators with a family history of prostate cancer and who had worked with coumaphos had a 65 percent increased risk of prostate cancer relative to those who never used the pesticide. This association was not found in men whose relatives did not have prostate cancer in the past. In addition, cumulative exposure to coumaphos was not associated with the risk of prostate cancer or all cancers combined.

Researchers collected data on 47,822 licensed pesticide applicators in Iowa and North Carolina. Cancer cases were determined using state cancer registries and exposure data were collected using questionnaires.

Although the U.S. Environmental Protection Agency does not consider coumaphos to be a carcinogen and animal studies found no evidence of carcinogenicity, inactive ingredients mixed with the insecticide may be responsible for the increased risk of prostate cancer risk.

In humans, exposure to coumaphos has been associated with other cancers, such as glioma, a type of brain cancer, and non-Hodgkin lymphoma.

The researchers speculate that the increased risk could be due to genetic susceptibility since only men with a family history of prostate cancer had an increased risk. Other explanations, including the possibility that the reported result may be due to chance, are also plausible.