A new study has found a possible link between a common industrial chemical and a higher risk of Parkinson’s disease.
The chemical, called trichloroethylene (TCE), has been used for many years in dry cleaning, metal cleaning, and other industrial jobs.
Even though it has been banned in some cases, it is still used in many places and can stay in the air, water, and soil for a long time.
The study was published in the October 1, 2025, issue of the medical journal Neurology. Researchers found that people who were exposed to higher levels of TCE in the air had a slightly higher chance of developing Parkinson’s disease. While the study does not prove that TCE causes Parkinson’s, it does show a connection that needs more research.
The research team, led by Dr. Brittany Krzyzanowski from the Barrow Neurological Institute in Phoenix, looked at health records from Medicare to find people over the age of 67 who were newly diagnosed with Parkinson’s between 2016 and 2018.
They compared each person with five others of similar age who did not have Parkinson’s. After collecting all the data, they had information on over 221,000 people with the disease and more than 1.1 million without it.
To figure out how much TCE each person might have been exposed to, the scientists used data from the U.S. Environmental Protection Agency. They matched this with the area where each person lived, using detailed ZIP code information. They looked at outdoor TCE levels from 2002, two years before the Parkinson’s diagnoses.
The participants were divided into ten groups based on how much TCE was in the air where they lived. The group with the lowest exposure had between 0.005 and 0.01 micrograms per cubic meter of air. The highest group had between 0.14 and 8.66 micrograms.
After adjusting for things like age, smoking history, and air pollution, the researchers found that people in the highest exposure group had a 10% higher risk of developing Parkinson’s compared to those in the lowest group.
They also found certain parts of the country had higher TCE levels. These “hot spots” were mostly in the Rust Belt region of the U.S., an area known for heavy industry. The researchers took a closer look at the areas around three major TCE pollution sites. In two of those places, the risk of Parkinson’s went up the closer people lived to the site.
Dr. Krzyzanowski pointed out that although the increased risk is small, the number of people exposed to TCE is so large that the public health impact could still be big. She said this shows the need for better rules and monitoring of harmful chemicals in the environment.
The study did have some limits. It only included older people on Medicare, so the results might not apply to younger people or those who get Parkinson’s at an earlier age. Also, it only looked at outdoor air levels from 2002 and didn’t consider exposure inside homes or over a person’s entire life.
Still, this research is an important step in understanding how pollution may affect brain health. It was supported by several groups, including the U.S. Department of Defense and the Barrow Neurological Foundation.
If you care about Parkinson’s disease, please read studies about how to improve walking in people with Parkinson’s disease and Scientists find causes of Parkinson’s and Lewy body dementia.
For more about Parkinson’s disease, please read studies These common drugs may increase risk of Parkinson’s disease and Researchers find an important cause of Parkinson’s disease.
The study is published in Neurology.
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