Environmental Toxicants and Parkinson Disease

Dr. Margarita Fedorova discusses possible environmental exposures and their risk of Parkinson disease. 

Show citation: 

Dorsey ER, De Miranda BR, Hussain S, et al. Environmental toxicants and Parkinson's disease: recent evidence, risks, and prevention opportunities. Lancet Neurol. 2025;24(11):976-986. doi:10.1016/S1474-4422(25)00287-X 

Show transcript: 

Dr. Margarita Fedorova:

Welcome to Neurology Minute. My name is Margarita Fedorova and I'm a neurology resident at the Cleveland Clinic. Today, we're reviewing some information about possible environmental exposures and their risk of Parkinson disease. As we see in diagnose patients with Parkinson, they often want to know why they developed it and some emerging studies may offer insights. A recent personal view published in The Lancet Neurology by Ray Dorsey and colleagues in November 2025 examined associations between three environmental exposures and Parkinson's disease; pesticides, dry cleaning chemicals and air pollution. Since only five to 15% of Parkinson's cases have an identifiable genetic cause, environmental factors are an important area of investigation. Dorsey and colleagues describe studies showing that pesticide exposure is associated with Parkinson's risk.

One example is Paraquat, an herbicide widely used in agriculture. It's banned in over 30 countries, but remains legal in the United States. In a population-based US study, residents living or working near areas where Paraquat was sprayed at twice the risk of developing Parkinson's, suggesting residential proximity alone may confer risk.

Other pesticide exposures may show similar patterns. The organic chlorides, DGT and gildren are used in various agricultural areas. They're fat-soluble compounds that accumulate over decades. Postmortem studies found that when brains with lewd pathology and some studies suggest developmental exposure may increase risk of neurodegeneration years later. There have also been risks possibly associated with chemicals used in dry cleaning and metal degreasing. Trichloroethylene or TCE is one such chemical that was found in high amounts in the water at Camp Lejeune in North Carolina. A study of over 170,000 marines stationed there showed a 70% increase in risk of developing Parkinson's compared to marines at a non-contaminated base. What's particularly striking is the timing. Marines were exposed at an average age of 20 and the exposure lasted just over two years, yet disease manifested 34 years later. This suggests a long latency period between exposure and disease onset.

TCE is also concerning because it evaporates from contaminated groundwater and can seep into buildings. As of 2000, 30% of US groundwater was contaminated with TCE. The third category of environmental exposure is air pollution. Studies from Canada, South Korea, Taiwan, and the UK show association between exposure to fine particular matter known as PM 2.5 in nitrogen dioxide with increased Parkinson's risk. These pollutants come from vehicle emissions, industrial sources, and combustion processes. The studies suggest that chronic exposure to these air pollutants may contribute to neurodegeneration through inflammatory and oxidative stress mechanisms. Unlike pesticides and dry cleaning chemicals, the magnitude of increased risk is often modest, typically ranging from one to 20%. However, the potential impact at large since almost everyone worldwide, 99% of people breathe on healthy air.

For us as clinicians, this underscores the importance of taking detailed environmental histories. When patients ask, "Why me?" We can acknowledge that environmental exposures may have contributed to their disease. It's important to note that these studies show associations, but they don't confirm clear causation. Regardless, they may provide some answers to patients asking about the etiology of their Parkinson's or even the risks to others.

That's your neurology minute for today. Keep exploring and we'll see you next time. If you want to read more, please find the paper by Ray Dorsey, titled Environmental Toxicants and Parkinson's Disease: Recent Evidence and Prevention Opportunities, published online in The Lancet Neurology in November 2025.