Three times more likely to fall ill Study examines agricultural link
Oct. 12, 2006. 01:00 AM
Women who have worked on farms are almost three times more likely to develop breast cancer than those who have never worked in agriculture, a new study of cancer patients in the Windsor area suggests.
The paper, to be published today in the Annals of the New York Academy of Sciences, says women with farming experience are 2.8 times more likely to develop the disease than non-farmers and that the agricultural link may linger long after a woman has gone on to other occupations.
Study author James Brophy, an occupational and environmental health scientist, theorizes that exposure to pesticides, or other common farm contaminants, may explain the increased risk.
The study was conducted over 2 1/2 years and looked into the lives of 564 women diagnosed with breast cancer at the Windsor Regional Cancer Centre, said Brophy, who is also executive director of the Occupational Health Clinic for Ontario Workers in Sarnia. Of those 564 patients from Essex and Kent counties, 154 had worked on farms. Those patients were compared to an equal number of women in the same area who did not have any form of cancer.
After weeding out traditional breast cancer risk factors such as genetics, smoking, age, number of children and hormone replacement therapies the farming link was apparent, said Brophy.
“We also found that if she went on to work in health care or in auto (manufacturing) her breast cancer risk continued, and in the case of the auto industry, it actually slightly increased.”
Brophy said there have been a couple of previous studies that have also shown a link between agriculture and breast cancer. But “there is a significant gap in our understanding of work-related exposures and breast-cancer risk.” he wrote in the paper’s introduction.
“I’m not saying we have the smoking gun on breast cancer. We don’t,” said Brophy, who conducted the study with Dr. Margaret Keith. “What I think we do have is a study that shows the importance of looking at occupation as a potential risk factor and that something is going on… within the rural population.”
Heather Logan, head of cancer control policy with the Canadian Cancer Society, said much more must be done to study occupational links to the disease, and Brophy’s paper could point the way.
“The whole way they’ve approached this study is really quite remarkable,” Logan said. “And it raised really important questions, not just about women’s work history, but our ability to understand the previous work history in both men and women and the potential risk of developing cancer as a result.”
Ann Chambers, a professor of oncology at the University of Western Ontario’s Schulich School of Medicine and Dentistry, said it was a “good study” that should prompt further research. But Chambers, who specializes in breast cancer, said it was important to understand the association found in the study between cancer and farming does not necessarily mean there’s a causal relationship between the two.
“The real danger that the public has in this sort of thing is that you see an association and then they think, `Aha, working on a farm causes cancer,'” she said. “And the study statistically can’t say that. It says there is an association which warrants further study to understand what the cause is.”
Brophy agreed further research must be conducted to see if the association holds true outside of the Windsor area and he is currently expanding his sample size to 1,000 women.
He said the study groups all forms of agriculture together and cannot determine if one type of farming is more dangerous than another.
Brophy said a host of environmental contaminants, like diesel fumes, antibiotics and growth hormones are common in agricultural settings and could also be contributing to the higher cancer rates.