Trichloroethylene exposure increases Parkinson’s risk
Long-term exposure to trichloroethylene, a widely used industrial solvent, is now linked to a higher likelihood of developing Parkinson’s disease.
A new nationwide study suggests that long-term exposure to the industrial degreasing chemical trichloroethylene (TCE) may slightly raise the risk of Parkinson’s disease. While the increase in individual risk is modest, the widespread presence of TCE in air, soil, and water means that the potential population impact could be substantial.
Study Details
Researchers from the Barrow Neurological Institute analyzed Medicare data covering more than 1.3 million older adults in the United States between 2014 and 2018. They compared 221,789 people diagnosed with Parkinson’s disease to 1.1 million control participants of similar age and background.
Exposure estimates came from the U.S. Environmental Protection Agency’s National Air Toxics Assessment, which maps average levels of pollutants across ZIP codes. The team focused on trichloroethylene, a solvent commonly used in metal cleaning, paint removers, adhesives, and automotive products.
TCE is a persistent pollutant that can linger in the environment for years. It enters the air, water, and soil and is known to accumulate in indoor spaces through vapor intrusion. Despite existing safety measures, a 2000 EPA report found traces of TCE in roughly 30% of U.S. drinking water supplies.
Methodology
The study used a population-based, case-control design. Researchers estimated each participant’s exposure to TCE based on their residential ZIP code two years before diagnosis. Most participants had lived in the same area for at least eight years, strengthening the exposure link.
They then analyzed whether people in ZIP codes with the highest TCE concentrations (ranging from 0.14 to 8.66 micrograms per cubic meter) had a greater risk of Parkinson’s compared to those in areas with the lowest levels (0.005 to 0.01 micrograms per cubic meter).
Key Findings
People in the highest exposure group had a 10% greater risk of developing Parkinson’s disease compared to those in the lowest exposure group.
The risk increase was dose-dependent, meaning higher pollution levels were tied to higher Parkinson’s rates.
Those living near TCE-emitting industrial facilities showed more cases of gait instability, falls, and dementia early signs often seen before a Parkinson’s diagnosis.
The Rust Belt region of the U.S. showed the highest levels of ambient TCE, aligning with areas that have long histories of manufacturing and industrial activity.
Parkinson’s risk decreased as residents lived farther from major TCE-emitting sites.
Implications for Practice
For patients and families:
This study supports growing evidence that environmental factors may influence Parkinson’s risk. People living near industrial or contaminated areas may consider checking local environmental quality reports or community health advisories. While this study does not change treatment recommendations, awareness and advocacy for cleaner environments can support prevention efforts.
For healthcare providers:
Clinicians may want to include environmental exposure history such as residence near industrial plants or groundwater contamination sites in Parkinson’s assessments. This is especially relevant for patients presenting with prodromal symptoms such as mild tremor, gait disturbance, or unexplained falls.
For policymakers and public health officials:
While the U.S. EPA plans to restrict most uses of TCE, contamination from historical sites remains widespread. Long-term remediation, soil vapor monitoring, and community notifications remain critical to reducing ongoing exposure. The findings highlight how reducing industrial emissions can have long-lasting effects on neurological health.