GLP spaces on X: Pesticides cause Parkinson’s? Another scandalous chemical claim misses the mark

Like so many other chemical scare stories, the claim that pesticides cause Parkinson’s disease (PD) has circulated online for years, without credible evidence to substantiate the connection. While some questionable studies suggest associations, they fall far short of proving causation due to methodological limitations and inconsistent findings. In early May, one such study swept through the headlines, declaring that people who live close to golf courses have a higher risk of Parkinson’s owing to the elevated use of herbicides to control weeds.

The chief problem with the research — although there were many unjustified assumptions behind the study — was that the authors used proximity to a golf course as evidence of exposure. In effect, they assumed what they needed to demonstrate. Meanwhile, higher quality research based on robust data has failed to provide any evidence that any currently used pesticide causes or contributes to PD.

Speculative animal studies have also investigated pesticides like rotenone and paraquat, which can induce Parkinson’s-like symptoms in rodents. Yet, these experiments use extremely high doses and direct administration methods that don’t reflect typical human exposure. Human pesticide exposure is generally chronic and very low-level, making it unreasonable to extrapolate animal findings to human health.

Moreover, not all exposed individuals develop Parkinson’s, suggesting other factors, like genetic mutations, play a significant role. Clinical and neuropathological evidence also fails to confirm a direct link. Parkinson’s involves the loss of dopaminergic neurons and Lewy body formation, but no consistent biomarker ties these processes specifically to pesticides. Many environmental and lifestyle factors could contribute to neurodegeneration, and singling out pesticides greatly oversimplifies the disease’s etiology.

Without consistent, high-quality evidence, causation remains unproven. The complex interplay of genetics, environment, and aging likely drives Parkinson’s, with pesticides, at most, as one of many potential risk factors.

Join GLP founder Jon Entine and longtime contributors Liza Dunn and Cameron English as they discuss the alleged link between pesticides and Parkinson’s. Follow this link or listen to the conversation below:

I couldn’t join this space live, but I jest listening to replay.

Another informative, balanced and evidence based space from @DrLizaMD and the team.

Thoroughly enjoyable! https://t.co/XWb2uSFhTE

— Simon Maechling (@simonmaechling) May 18, 2025

Dr. Liza Dunn is a medical toxicologist and the medical affairs lead at Bayer Crop Science. Follow her on X @DrLizaMD

Jon Entine, founder and executive director of the Genetic Literacy Project, is an Emmy-winning investigative TV News producer and author of seven books, including three on genetics. Please follow him on X at @JonEntine

Cameron J. English is the director of bio-sciences at the American Council on Science and Health. Visit his website and follow him on X @camjenglish