Pesticide link to prostate cancer
Agricultural workers who apply pesticides to crops may be at increased risk of developing prostate cancer.
An American study of over 55 000 men who are exposed pesticides through their work on farms, in warehouses or grain mills, recorded 566 new prostate cancers diagnosed between 1993 and 1999, representing a 14% greater risk than that suffered by the area’s general population.
The latest research from the Agricultural Health Study focused on 45 pesticides, seven of which were identified as possible risk factors.
Methyl bromide posed the greatest threat, appearing to increase the risk of prostate cancer for all exposed through its application, it is reported in the American Journal of Epidemiology.
Scientists found that the risk of prostate cancer increases with frequency of exposure to the fumigant gas, which is used across the US to protect crops from pests in the soil and to fumigate grain bins and other agricultural storage areas.
A clutch of other pesticides – chlorpyrifos, coumaphos, fonofos, phorate, permethrin, and butylate – were implicated as additional risk factors, but only amongst men with a family history of prostate cancer.
Because the increased risks associated with these six chemicals is restricted to a subgroup of the entire population exposed, the results are particularly difficult to interpret, as the elevated risks for farm workers with this genetic background may have another unrelated cause.
“We cannot rule out the possibility that our observation occurred by chance alone,” cautioned the study’s author, Aaron Blair, who is chief of the Occupational and Environmental Epidemiology Branch in NCI’s Division of Cancer Epidemiology and Genetics.
“Clearly, these findings need to be replicated. But, the internal consistency of our findings does not allow us to dismiss these results.”
His colleagues point out that the very similar chemical structure shared by four of these six pesticides suggest that they may interact with a particular form of genes shared by men with a family history of prostate cancer, a possible mechanism that heightens the risk of developing the
disease.
Previous studies have shown a link between pesticide use and prostate cancer among agricultural workers, with farming listed as the most consistent occupational risk factor for prostate cancer.
Further, the National Institute for Occupational Safety and Health lists methyl bromide as a potential occupational carcinogen.
However there is massive number of other possible confounding environmental risk factors to which agricultural workers are exposed, including engine exhausts, solvents, animal viruses, fertilizers, and particular microbes, which has clouded the conclusions of previous studies.
It is hoped that the Agricultural Health Study – a collaboration between the NCI, the National Institute of Environmental Health Sciences, and the Environmental Protection Agency – will help evaluate the real risks by continuing to collect detailed information on specific exposures from nearly 90 000 participants from North Carolina and Iowa.
