• Posted October 2, 2025

Industrial Chemical Linked To Parkinson's Disease

Long-term exposure to a chemical used in metal degreasing and dry cleaning might increase the risk of Parkinson’s disease, a new study says.

Seniors living in places with the highest airborne levels of trichloroethylene showed a 10% higher risk for Parkinson’s than those in areas with the lowest levels, researchers report in the journal Neurology.

Further, risk of Parkinson’s increased fourfold for people living one to five miles downwind of an Oregon factory that used the chemical, researchers found.

“Long-term exposure to trichloroethylene in outdoor air was associated with a small but measurable increase in Parkinson’s risk,” said lead researcher Brittany Krzyzanowski, an assistant professor at the Barrow Neurological Institute in Phoenix.

“These findings add to a growing body of evidence that environmental exposures may contribute to Parkinson’s disease,” she said in a news release.

Trichloroethylene (TCE) is known to cause kidney cancer, and studies have linked the chemical to blood cancers and liver cancer, according to the National Cancer Institute.

It’s a persistent environmental pollutant in air, water and soil across the United States, researchers noted. A 2000 U.S. Environmental Protection Agency  (EPA) report estimated that up to 30% of the nation’s drinking water supplies were contaminated with TCE. 

In 2024, the EPA issued a ban on the chemical for all consumer and commercial uses that was set to start in 2025. However, the ban was stayed pending a legal challenge, and the chemical remains in use.

For the new study, researchers used Medicare data to identify seniors older than 67 newly diagnosed with Parkinson’s between 2016 and 2018, and compared each participant to five other seniors who didn’t have the disease.

Parkinson’s occurs when brain cells that produce the neurotransmitter dopamine either die or become impaired. When that happens, people start to have movement problems that include shaking, stiffness, and difficulty with balance and coordination, according to Cleveland Clinic.

All told, the study included nearly 222,000 people with Parkinson’s and more than 1.1 million people without the disease, researchers said.

Using ZIP codes and EPA data, researchers mapped everyone’s exposure to outdoor TCE concentrations two years prior to their diagnosis.

Researchers concluded that people exposed to the highest levels of TCE appeared to have a greater risk of Parkinson’s, after controlling for other risk factors for the disorder.

“While the increased risk was modest, the sheer number of people exposed to TCE in the environment means the potential public health impact could be substantial,” Krzyzanowski said.

The team also identified several geographic “hot spots” where outdoor TCE levels were highest, particularly in the Rust Belt region, as well as three facilities that operated as the nation’s top TCE-emitting facilities in 2002.

Results showed that Parkinson’s risk was higher close to two of the three facilities. 

At one of those sites, Parkinson’s risk clearly rose the closer people lived to the facility. People living one to five miles downwind from a lithium battery plant in Lebanon, Oregon, had a more than four times greater risk of Parkinson’s than those living up to 10 miles away.

“This underscores the need for stronger regulations and more monitoring of industrial pollutants,” Krzyzanowski said.

The researchers noted that their study could not draw a direct cause-and-effect link between TCE and Parkinson’s. Their results only show an association.

However, previous reports have also linked TCE to Parkinson’s, researchers said.

For example, TCE contamination of the drinking water at Camp Lejeune, a Marine Corps base in Jacksonville, N.C., has been linked with a 70% higher risk of Parkinson’s among service members stationed there.

More information

The U.S. Environmental Protection Agency has more on trichloroethylene.

SOURCES: American Academy of Neurology, news release, Oct. 1, 2025; Neurology, Oct. 1, 2025