A chemical used to degrease metal, clean clothes and, historically, even decaffeinate coffee is increasingly tied to Parkinson’s disease. The solvent, trichloroethylene (TCE), persists in air, soil and groundwater and can seep as vapor into homes and workplaces, the University of Rochester Medical Center reports. Researchers say exposure is common—and the connection to Parkinson’s is growing harder to ignore.

Trichloroethylene (TCE) is a common solvent linked to Parkinson’s disease. It is found in chemicals used on military bases.

Large Human Studies Show Elevated Risk

Among U.S. Marines and Navy personnel who trained at Camp Lejeune when base water was heavily contaminated, the rate of Parkinson’s was about 70% higher than in a comparable group stationed elsewhere, according to a study summarized by Science. The same research team noted more early “prodromal” symptoms—such as loss of smell—among the exposed cohort, suggesting risk can persist and emerge decades after contact, UCSF reports.

Zooming out beyond military settings, a nationwide analysis linked higher outdoor TCE exposure to a measurable bump in Parkinson’s diagnoses. People in the top exposure bracket were about 10% more likely to develop the disease than those in the lowest, Euronews reports.

The chemical has been used in metal degreasing, dry cleaning, and decaffeination.

How TCE Might Damage the Brain

TCE is lipophilic—it crosses biological membranes and reaches brain tissue. Animal studies show it can injure dopamine-producing neurons in the substantia nigra, the same cells lost in Parkinson’s. Proposed mechanisms include mitochondrial complex I inhibition, oxidative stress, neuroinflammation and abnormal alpha-synuclein changes, according to a comprehensive review in the Journal of Parkinson’s Disease. Those findings align with human epidemiology and strengthen biologic plausibility.

Exposure Is Wider Than Many Realize

TCE has contaminated numerous industrial and military sites, and it can migrate as underground plumes that reach far from original sources. It evaporates into indoor air through cracks and utility lines in a process known as vapor intrusion. Measurable amounts show up in a substantial share of U.S. drinking water systems, and past consumer uses were widespread, URMC reports. These environmental pathways mean risk is not limited to workers who handle solvents directly.

TCE contaminates groundwater, air, and soil at military bases and across the United States.

Regulatory Momentum—and What Individuals Can Do

In December 2024, the U.S. Environmental Protection Agency announced a ban on nearly all uses of TCE, a major step toward reducing future exposure, according to The Michael J. Fox Foundation. Policy change won’t erase legacy contamination, though. Communities near former dry cleaners, aerospace facilities or military bases may still face vapor intrusion or tainted groundwater.

Practical steps help. If you live or work near a known plume or cleanup site, consider indoor air testing and, where indicated, sub-slab depressurization systems similar to those used for radon. Ask local water utilities for contaminant reports. Workers should follow solvent-safety protocols and push for safer alternatives. These actions complement the public-health gains expected from national restrictions—and reflect what the science now signals about TCE and Parkinson’s.

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