A new study looking at exposure to pesticide and Parkinson’s disease rates in Nebraska found the two to be strongly linked but also concluded that exposure most likely isn’t the sole factor in the development of the chronic and progressive nervous system disorder.
University of Utah geographer Neng Wan mapped out land usage and pesticide application data, then calculated the amount of exposure Nebraskans would have had to 20 agricultural pesticides. He then compared that to publicly available reports of Parkinson’s disease in Nebraska.
Parkinson’s affects movement and usually is associated with tremors and impaired motor function. Other symptoms can include hallucinations and delusions.
Nebraska leads the world in the prevalence of Parkinson's disease per capita, according to research quoted on the Creighton University School of Medicine website.
Wan chose to look at Nebraska for several reasons, he said during a recent interview and in a paper on his research published Oct. 30 in the Journal of Rural Health.
Nebraska is one of the top ag states in the country: 93 percent of it is dedicated to farm and ranches. An estimated 15 million kilograms of pesticide was applied in Nebraska in 2015, according to the U.S. Department of the Interior’s Geological Survey.
It’s also the only state with a population-based registry of Parkinson’s, thanks to 1996 legislation that required doctors to report the disease.
Wan's research found two hot spots for Parkinson’s in the state, one centered on 10 southeastern counties known for row crop farming and the other in four western Nebraska counties where ranching dominates.
He concludes that the western hot spot, where pesticide use tends to be lower, suggests other factors are contributing to the high number of Parkinson’s cases there. But for the rest of the state, the rate strongly correlates with increased exposure to pesticide chemicals, including alachlor and broxomy.
While the study showed a statistically significant connection, pesticide exposure likely is not the sole factor in the risk of people to develop the disease, Wan said in the article.
“Other environmental and lifestyle factors may also contribute,” he wrote. “The development of PD is a complex process that involves genetic, environmental and personal aspects.”
Other studies have also found Parkinson’s disease among livestock farmers and suggested a connection to some of the chemicals they use.
While researchers have long known of and studied the association between pesticides and Parkinson’s disease, the new research is the first to create and use state-level pesticide exposure maps in the United States.
Wan is careful to point out his research doesn’t imply that exposure causes the disease, but he says the work provides background for future studies that examine the causes of Parkinson’s.
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