The Agricultural Health Study
The Agricultural Health Study (AHS) is the largest, most comprehensive study of agricultural health conducted in the United States. Almost 90,000 people are participating in the Agricultural Health Study - about 31,000 from North Carolina and 59,000 from Iowa. Participants include certified private pesticide applicators (farmers) and their spouses in North Carolina and 
Iowa and certified commercial pesticide applicators (5,000) in Iowa only. Another important feature of the AHS is that it is one of the largest health studies of rural women ever conducted. About 3 percent of pesticide applicators in the study are women (1,359). Over half of the farmers’ spouses are active in farm work, including mixing and applying pesticides. The credibility of this study and the resulting research findings are high. Results were first released in late 2005 and new information was released in late 2006 and March 2007. The study will continue for at least another 10 years.
Previous studies of agricultural health indicated that farmers are healthier than the general population in some respects. For example, they live longer and are less likely to die from heart disease. Farmers are also less likely to die of some cancers such as lung, esophagus, bladder and colon. The study has made three general comparisons. First, investigators are comparing applicators and spouses to people in the general population of Iowa and North Carolina to see if there are differences in the cancer rates. Second, scientists compared applicators or spouses who have cancer or other diseases to those who don’t to see if there are pesticide exposure or other factors that may have contributed to the disease. Third, the scientists also are comparing applicators or spouses using a particular pesticide to those not using it to see if there are any differences in the risk of cancer or other health problems.
For cancer, investigators compared the rate of various types of cancer in applicators and spouses to the rates of those cancers in the general population of those states, adjusting for age and gender. Applicators are healthier than the general population and the overall rate for all types of cancer is lower than in the general population. The rates for 18 of 20 specific cancers are lower in applicators and spouses than in the general population. For prostate cancer, the rate is 14 percent higher in male applicators than in the general population, while the rate of skin melanomas is 50 percent higher among farm wives than in the general population. The scientists found no evidence of an association between breast cancer in farmers’ wives and exposure to any of 50 pesticides evaluated. Breast cancer risk was not increased with husband’s use of 2,4-D.
Diazinon was associated with a higher breast cancer risk with use by husbands, but ONLY in women with a family history of the disease, suggesting a possible gene-environmental interaction.
Wheeze is a symptom of respiratory conditions, especially asthma. A wheezing sound is produced when you breathe if the airways deep in your lungs are narrowed. The scientists took into account known risk factors for wheeze, including asthma or allergies and smoking history, and were able to separate any impact of these influences from that of pesticides. With that in mind, the scientists learned that wheeze was associated with several types of farm exposures, including eight pesticides - paraquat, EPTC, parathion, malathion, chlorpyrifos, atrazine and alachlor, as well as with applications involving fogging and misting animals. Wheeze also was associated with other exposures on the farm, including using diesel tractors and frequent solvent use. Certain animal production practices also were associated with wheeze, including egg and dairy production and the daily performance of livestock/veterinary procedures.
Retinal degeneration is the leading cause of vision loss in older adults, but little is known about its causes. The most common form of retinal degeneration is macular degeneration, characterized by less visual acuity and loss of central field of vision. Agricultural health study scientists found a consistent association between applicators who reported retinal degeneration and use of fungicides. The association got stronger with increasing lifetime-days of fungicide use. New information in the last few months has associated these fungicide active ingredients with retinal degeneration: benomyl, captan, chlorothanonil, copper ammonia carbonate, ferbam, maneb, metalaxyl, PCNB and sulfur. A second study looked at the relationship between retinal degeneration and pesticide use in farm wives and found the same results. The wives were nearly twice as likely to have retinal degeneration if they or their husbands used fungicides. The fungicides that drove this association were maneb, manocozeb and ziram.
The AHS has given scientists a unique opportunity to learn more about female reproductive health. In their studies, the scientists focused on women aged 21-40 years old. They learned that women who used pesticides of any type were more likely to experience longer menstrual cycles and missed periods. When they looked at those women who used pesticides thought to act like hormones (based on toxicology studies in animals), they saw even stronger associations with long cycles and missed periods. The probable hormonally-active pesticides included in the study were lindane, atrazine and mancozeb or maneb. (University of Nebraska Crop Watch Newsletter, 4/6/07).
