A comprehensive long-term study of 90,000 American farmers should help make farming a safer way to make a living, says a U.S. health researcher.
The Agricultural Health Study, which has been under way since 1997, explores potential links between pesticide exposure and the incidence of cancer and other diseases among farmers and their families.
But what’s learned from the study could benefit more than just farmers, said Aaron Blair of the U.S. National Cancer Institute, one of the lead researchers involved in the study.
“Everyone is exposed to pesticides,” he said in an interview during a rural health conference in Saskatoon. “It’s pervasive in our society.”
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Devising a study to assess the impact of pesticides on the general population would be difficult, so focusing on a group that uses them regularly is the best way to gather information.
“It’s like the canary in the coal mine,” he said. “You study farmers, and if you find something there, then you decide whether you have to worry about what happens in the general population.”
The study involves about 85,000 farmers and spouses, along with about 5,000 commercial pesticide applicators, in Iowa and North Carolina.
All the participants have provided researchers with detailed information about their health, lifestyle and farming practices, with a special emphasis on their exposure to pesticides.
The participants will be re-interviewed periodically and provide biological samples. They will be monitored for the incidence of cancer and other diseases such as asthma, neurological disease, rheumatoid arthritis and reproductive problems.
If disease occurs, the data can be assessed to determine what if any link there may be to the use of certain pesticides.
Blair said that overall, farmers have better health and lower mortality rates than the general population, something that likely reflects the fact that they smoke less, drink less alcohol and have a more active, healthier lifestyle.
For example, the rate of lung cancer among farmers who smoke is lower than it is among the general population, including smokers.
“Farmers have some very good life habits that help protect them against a lot of diseases,” Blair said.
But at the same time, there is a “reasonable amount of evidence” that farmers have elevated rates of certain types of site-specific cancers, including lymphoma, multiple myeloma and cancers of the brain, stomach and prostrate.
“So it’s important to understand what’s going on, both why they have low rates for some things and high rates for others.”
The first major results from the AHS, published earlier this year, found 14 percent more cases of prostate cancer among the 55,332 male licensed pesticide applicators enrolled in the study than would be expected based on prostate cancer rates in the general population.
The study showed no increased risk associated with most of the 45 common pesticides studied.
But there was an increased risk with the fumigant methyl bromide and an increased risk for six other pesticides among those who had a family history of prostate cancer.
Blair noted that it’s just as important to be able to show that specific agricultural chemicals don’t cause cancer as that they do.
He also said there has been a major change in attitude toward the issue over the past few decades.
When he started doing his research in the 1970s, he’d often hear from farmers, distributors and manufacturers that pesticides were perfectly safe.
“You don’t hear that anymore,” he said.
“You hear, ‘it’s safe if used properly.’ That’s a watershed change in philosophy, and it’s the right one.”
Last month’s conference, organized by the University of Saskatchewan’s Institute for Agricultural, Rural and Environmental Health, brought together scientists from around the world to talk about their latest research into issues relating to farming and health.
Among the findings reported at the conference from other studies:
- There was no significant association between pesticide exposure and the risk of stomach or esophageal cancer among Nebraska farmers.
- Among farmers in six Canadian provinces, the risk of Hodgkin’s disease is more dependent on family history and smoking than pesticide exposure and smoking.
- Farmers in New York state were at no significantly increased risk for most cancers, although their higher age-adjusted rates for prostate cancer, melanoma and leukemia merit further study.
- Farmers and pesticide applicators exposed to chlorpyrifos showed increased risk of lung cancer.
