Study Links Trichloroethylene Exposure to Increased Parkinson’s Risk in Older Adults
A recent nationwide study has found an association between long-term exposure to the industrial solvent trichloroethylene (TCE) and a slightly increased risk of Parkinson’s disease in individuals over the age of 67. Researchers emphasize the study demonstrates a correlation, not causation.
The research, published in the journal Neurology, analyzed data from over 221,000 Medicare beneficiaries newly diagnosed with Parkinson’s between 2016 and 2018, comparing them to over 1.1 million individuals without the disease.Researchers, lead by Brittany krzyzanowski, PhD, of Barrow Neurological Institute in Phoenix, utilized U.S. Environmental Protection Agency data and participants’ residential ZIP+4 codes to estimate TCE exposure levels based on U.S. Census tract information. exposure estimates reflected air concentrations two years prior to diagnosis.
Participants were categorized into ten groups based on estimated TCE exposure, ranging from 0.005 to 8.66 micrograms per cubic meter (μg/m). After accounting for factors known to influence Parkinson’s risk – including age, smoking history, and exposure to fine particulate air pollution – the study revealed that individuals in the highest exposure group had a 10% increased risk of developing parkinson’s compared to those in the lowest exposure group.
The study also pinpointed geographic areas with elevated TCE levels, notably in the Rust belt and other localized regions across the U.S. Analysis of areas surrounding the three largest TCE-emitting facilities in the U.S.(data from 2002 was used) showed increased Parkinson’s risk closer to two of the facilities, with a clear dose-response relationship observed at one site – meaning risk increased with proximity to the facility.
“While the increased risk was modest, the sheer number of people exposed to TCE in the surroundings means the potential public health impact could be significant,” stated Krzyzanowski. She highlighted the need for stricter regulations and enhanced monitoring of industrial pollutants.
Researchers acknowledge limitations to the study. The focus on Medicare beneficiaries means the findings may not be generalizable to younger populations or individuals with early-onset Parkinson’s. Furthermore, TCE exposure was estimated using 2002 air quality data and doesn’t account for individual lifetime exposure or indoor concentrations.
The study was funded by the U.S. Department of Defense, the Kemper and Ethel Marley Foundation, Barrow Neurological Foundation, and the Moreno Family Foundation.
Source: American Academy of Neurology (https://www.aan.com/PressRoom/Home/PressRelease/5287)
Journal Reference: Krzyzanowski, B., et al. (2025). Ambient Trichloroethylene Exposure and Parkinson Disease Risk in Medicare Beneficiaries. Neurology. https://doi.org/10.1212/wnl.0000000000214174
