FAME drew data from the Agricultural Health Study, a larger project that tracked more than 80,000 farmers, agricultural workers, and their spouses. FAME researchers identified 115 individuals who had developed Parkinson’s, studying 110 of these individuals who were open to providing information on the herbicide they frequently used.
Syngenta held the findings in contention, arguing that because only 115 individuals developed Parkinson’s out of more than 80,000 North Carolinians and Iowans included in the Agricultural Health Study, direct correlation between Paraquat and an increased risk of developing Parkinson’s could not be proven. “The incidence of Parkinson’s disease [in the study] appears to be lower than in the general U.S. population,” explained Syngenta, trying to rationalize their website’s claim.
Dr. Caroline M. Tanner, the director of the Parkinson’s Disease Research, Education and Clinical Centers at the San Francisco Veterans Affairs Medical Center and the lead author of the FAME study explained that Syngenta’s argument held no basis. Tanner argued that FAME was not a comprehensive assessment of the incident Parkinson’s among all 80,000 individuals. Rather, the study chose a group of people who did have Parkinson’s – studying that specific group against a control group.
In actuality, FAME relied on self-reporting from participants of the larger Agricultural Health Study. “There were probably quite a few people with Parkinson’s disease who did not enroll in our study,” explained Dr. Freya Kamel, a scientist at the National Institute of Environmental Health Sciences, a branch of the National Institutes of Health and a co-author of the FAME study.
Syngenta said it “went to significant lengths to attempt to access the data” from the FAME study so that the manufacturer could “gain as complete an understanding as possible of the study in the pursuit of scientific rigor.” Kamel called Syngenta’s analysis inappropriate.
Kamel found the FAME study data linking Paraquat to Parkinson’s “about as persuasive as these things can get.”
A similar study conducted in 2012 – the Genetic Modification of the Association of Paraquat and Parkinson’s Disease – found that individuals who used Paraquat and who also had a specific genetic variation were 11 times more likely to develop Parkinson’s, indicating that some people are put at greater risk by being exposed to the chemical.