The Troubling Link Between Pesticides & Parkinson's Disease Risk

If you do a quick internet search on pesticides and human health, frightening phrases like "possible carcinogen" and "nervous system harm" are aplenty. But how much does exposure raise the risk of certain diseases? And what can be done about it?

According to the abstract of the yet-to-be-published study, researchers found that the application of 14 pesticides from 1992 to 2008 was strongly associated with Parkinson's disease (PD) risk in rural counties in the Rocky Mountain and Great Plains region. Three pesticides in particular—simazine (an herbicide), lindane (an insecticide that has since been banned), and atrazine (an herbicide)—had the strongest relationship with PD.

The regions studied included parts of Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah, and Wyoming. People living in counties with the highest use of these three pesticides ran a 25-36% greater risk of Parkinson's than those with the lowest use (broken down, the risk was 36% higher for simazine, 25% for lindane, and 31% for atrazine).

To arrive at these findings, researchers analyzed data from 21,549,400 Medicare beneficiaries (ages 67+ in 2009). They then examined county-level United States Geological Survey estimates on pesticide use between 1992 and 2008.

"There was a modest dose-response relationship between PD risk and all three pesticides," the study states, meaning that the more pesticides used in a country, the greater the risk of Parkinson's disease among its residents.

Though individual exposure data was not collected, this research suggests that while people who work in farming may be more at risk of negative health impacts2 from pesticide exposure, those in surrounding areas may also be affected.

This new research will be presented at the American Academy of Neurology's 76th Annual Meeting next month. It's just the latest study to suggest that pesticide exposure may be associated with Parkinson's risk. One study from 2011 found a link between the pesticide rotenone and herbicide paraquat3 and Parkinson's disease risk as well. We've known that chemical exposure, in general, may correlate to Parkinson's development for nearly 40 years, since the mid-1980s4.

Each new finding paints a clearer picture of what chemicals need special attention and regulation for the sake of disease prevention.

The U.S. is less restrictive of pesticides than other nations. Of the 1.2 billion pounds of pesticides used in U.S. agriculture in 2016, approximately 322 million pounds were pesticides banned in the EU, 40 million pounds were pesticides banned in China, and nearly 26 million pounds were pesticides banned in Brazil, according to a 2019 report published in Environmental Health.

At this point, pesticides are essential to keeping global food systems running. Still, studies like these are equally frightening and important, giving us a deeper understanding of how these chemicals might be negatively impacting human health in the long run.