Pesticide and Herbicide Use Linked to Parkinson Disease Risk According to New Study

According to preliminary study results, regions of the United States where there is greater exposure to pesticides and herbicides have greater incidence of Parkinson disease (PD). The findings suggest that pesticide and herbicide exposure is linked to risk of developing PD. The farming practices in the Great Plains and Rocky Mountain regions were particularly associated with PD risk. The preliminary results will be presented at the 76th Annual Meeting of the American Academy of Neurology (AAN) in April 2024.

Researchers from the Barrow Neurological Institute in Phoenix, Arizona reviewed records from 21.5 million people from across the United States who enrolled in Medicare in 2009 to establish nationwide PD rates across different regions of the country. A comparison of these rates against regional usage of 65 different herbicides and pesticides revealed that counties in Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah, and Wyoming showed the strongest relationship between PD and herbicide and pesticide exposure. Researchers identified the strongest association between the herbicides simazine and atrazine and the pesticide lindane with the risk of developing PD.

Compared to people living in counties with the lowest exposure to these 3 agents:

• People with the greatest exposure to simazine were 36% more likely to have PD.
• People with the greatest exposure to atrazine were 31% more likely to have PD.
• People with the greatest exposure to lindane were 25% more likely to have PD.

Results were consistent regardless of other factors such as air pollution but were based on county-level estimates of pesticide and herbicide exposure rather than individual-level data. 

“It’s concerning that previous studies have identified other pesticides and herbicides as potential risk factors for Parkinson’s, and there are hundreds of pesticides that have not yet been studied for any relationship to the disease,” said study author Brittany Krzyzanowski, PhD. “Much more research is needed to determine these relationships and hopefully to inspire others to take steps to lower the risk of disease by reducing the levels of these pesticides.”

The Michael J. Fox Foundation for Parkinson’s Research provided support for this research.