A common cleaning chemical has quietly permeated groundwater, air, and everyday products, raising concerns about its long-term impact on human health.
A widely used industrial chemical may be contributing to the rapid rise of the world’s fastest-growing brain condition: Parkinson’s disease.
Trichloroethylene (TCE) has been widely used for more than a century in products and processes ranging from metal degreasing to fabric cleaning and even coffee decaffeination. Its use peaked in the United States in the 1970s, when more than 600 million pounds were produced annually, about two pounds per person.
Although its use has declined, its environmental legacy remains. The chemical has contaminated major sites across the country, including Camp Lejeune and numerous Superfund locations, and is found in a significant portion of U.S. groundwater.
Health Risks and Hidden Exposure
Health risks linked to TCE are well documented. It is a known carcinogen, associated with miscarriages and congenital heart defects, and tied to a 500 percent increased risk of Parkinson’s disease. What makes it particularly concerning is how easily exposure can occur without detection.
TCE does not stay contained. It seeps into soil and groundwater, forming underground plumes that can travel long distances and shift over time. One such plume on Long Island spans more than four miles (6.4 kilometers) in length and two miles (3.2 kilometers) in width, contaminating drinking water supplies.
It can also move upward into buildings. Because TCE evaporates readily, it can rise from contaminated ground into homes, schools, and offices through a process called vapor intrusion. This means people may inhale the chemical simply by occupying buildings above polluted sites. Despite this risk, routine testing for TCE is uncommon, unlike radon testing, which is now standard in many homes.
Emerging Links to Parkinson’s Disease
In a hypothesis paper published in the Journal of Parkinson’s Disease, researchers from institutions including the University of Rochester Medical Center argue that the chemical could be an overlooked driver of Parkinson’s Disease’s rapid growth worldwide.
Laboratory studies show that TCE can enter the brain and damage mitochondria, the structures that produce energy in cells. This damage particularly affects dopamine-producing neurons, whose loss is a defining feature of Parkinson’s disease. The chemical also appears to activate biological pathways, such as LRRK2 kinase activity, that are known to play a role in the disease, suggesting overlap between environmental and genetic risk factors.
Epidemiological findings support these biological insights. Individuals exposed to TCE through work or hobbies years earlier face a significantly higher risk of developing Parkinson’s. At Camp Lejeune, for example, service members exposed to contaminated water have about a 70 percent increased risk.
However, most exposure is not occupational. Researchers warn that millions of people encounter the chemical unknowingly through air, water, and indoor environments.
One of the biggest challenges in identifying TCE as a risk factor is timing. Parkinson’s disease often develops decades after exposure, making it difficult to trace its origins.
Environmental Exposure in Unexpected Places
Additional evidence comes from a study published in Movement Disorders, which examined attorneys who worked near a contaminated dry cleaning site in Rochester, New York.
The site, active from 1950 to 1994, released TCE and perchloroethylene (PCE) into the surrounding soil and groundwater. Just 300 feet (91 meters) away stood an 18-story office building where the attorneys worked, with groundwater flowing toward its underground garage.
Among 79 attorneys studied, four (5.1%) had Parkinson’s disease, compared to an expected rate of 1.7% based on age and sex. Although the difference compared to a separate comparison group was not statistically significant, it still exceeded what would typically be expected in the general population.
Nearly one in five attorneys (19.0%) had cancers linked to TCE exposure, compared to 5.3% in the comparison group. These included prostate cancer, kidney cancer, multiple myeloma, and non-Hodgkin’s lymphoma, all previously associated with the chemical.
Unlike factory workers, these individuals were professionals who may have been exposed simply by working in a nearby building. The findings suggest that environmental exposure, particularly through vapor intrusion, could pose risks in settings not traditionally considered hazardous.
Challenges in Measuring Long-Term Impact
The authors outline a series of steps to address the public health threat posed by TCE, noting that contaminated sites can be remediated and that indoor air exposure can be reduced with vapor mitigation systems similar to those used for radon. But with thousands of polluted sites still scattered across the United States, they argue that cleanup and containment efforts must move much faster.
They also call for expanded research into how TCE may contribute to Parkinson’s disease and other illnesses, along with closer monitoring of the chemical in groundwater, drinking water, soil, and both indoor and outdoor air, and clearer communication of those risks to affected communities.
In December 2024, the EPA finalized a rule to prohibit all uses of TCE, with most commercial and consumer uses originally slated to be banned within a year. But the rollout has been slowed by court challenges and administrative delays, and some limited uses tied to critical infrastructure and national security have received longer compliance timelines.
References:
“Trichloroethylene: An Invisible Cause of Parkinson’s Disease?” by E. Ray Dorsey, Maryam Zafar, Samantha E. Lettenberger, Meghan E. Pawlik, Dan Kinel, Myrthe Frissen, Ruth B. Schneider, Karl Kieburtz, Caroline M. Tanner, Briana R. Miranda, Samuel M. Goldman and Bastiaan R. Bloem, 14 March 2023, Journal of Parkinson’s Disease.
DOI: 10.3233/JPD-225047
“Dry-Cleaning Chemicals and a Cluster of Parkinson’s Disease and Cancer: A Retrospective Investigation” by E. Ray Dorsey, Dan Kinel, Meghan E. Pawlik, Maryam Zafar, Samantha E. Lettenberger, Madeleine Coffey, Peggy Auinger, Kevin L. Hylton, Carol W. Shaw, Jamie L. Adams, Richard Barbano, Melanie K. Braun, Heidi B. Schwarz, B. Paige Lawrence, Karl Kieburtz, Caroline M. Tanner, Briana R. de Miranda and Samuel M. Goldman, 23 February 2024, Movement Disorders.
DOI: 10.1002/mds.29723
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