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Vita gazette – Could Trichloroethylene (TCE), widely used daily, fuel the rise of Parkinson’s, the world’s fastest-growing brain disease? TCE is widely used today in dry cleaning and TCE in vapour degreasing.

As Italian scientists explained ago, “chemicals” may be another trigger for Parkinson’s. For the past 100 years, trichloroethylene (TCE) has been used to decaffeinate coffee, degrease metal, and dry clean clothes. And is associated with a 500% increased risk of Parkinson’s disease.

In a hypothesis paper in the Journal of Parkinson’s Disease, an international team of researchers (including University of Rochester Medical Center (URMC) neurologists Ray Dorsey, MD, Ruth Schneider, MD, and Karl Kieburtz, MD) postulate that TCE may be an invisible cause of Parkinson’s. In the paper, they detail the widespread use of the chemical, the evidence linking the toxicant to Parkinson’s, and profile seven individuals, ranging from a former NBA basketball player to a Navy captain to a late U.S. Senator, who developed Parkinson’s disease either after likely working with the chemical or being exposed to it in the environment.

A ubiquitous industrial pollutant

TCE was a widely used solvent in many industrial, consumer, military, and medical applications, including removing paint, correcting typewriting mistakes, cleaning engines, and anaesthetising patients. Millions of people worked with chemicals or other similar industrial solvents. While domestic use has since fallen, TCE is still used worldwide for degreasing metal and spot dry cleaning.

TCE contaminates countless sites in the world. For example, half of the most toxic Environmental Protection Agency’s Superfund sites contain TCE: the chemicals were used to clean electronics and computer chips: TCE is found in numerous military bases.

TCE and Parkinson’s disease

The connection between TCE and Parkinson’s was first hinted at in case of studies more than 50 years ago. In the intervening years, research in mice and rats has shown that TCE readily enters the brain and body tissue and, at high doses, damages the energy-producing parts of cells known as mitochondria. In animal studies, TCE causes selective loss of dopamine-producing nerve cells, a hallmark of Parkinson’s disease in humans.

Individuals who work directly with TCE have an elevated risk of developing Parkinson’s. However, the authors warn that “millions more encounter the chemical unknowingly through outdoor air, contaminated groundwater, and indoor air pollution.”

The chemical can contaminate soil and groundwater, leading to underground rivers or plumes extending long distances and migrating over time.

Beyond their water risks, the volatile TCE can readily evaporate and enter people’s homes, schools, and workplaces, often undetected. This vapour intrusion is likely exposing millions who live, learn, and work near former dry cleaning, military, and industrial sites to toxic indoor air. Vapour intrusion was first reported in the 1980s when radon was found to evaporate from soil and enter homes and increase the risk of lung cancer. Today millions of homes are tested for radon, but few are for cancer-causing TCE.

Decades before symptoms appear

The piece profiles seven individuals where TCE may have contributed to their Parkinson’s disease. While the evidence linking TCE exposure to Parkinson’s disease in these individuals is circumstantial, their stories highlight the challenges of building the case against chemicals. In these cases, decades have often passed between exposure to TCE and the onset of Parkinson’s symptoms.

Addressing the threat to public health

The authors note that “for over a century, TCE has threatened workers, polluted the air we breathe -outside and inside- and contaminated the water we drink. Global use is waxing, not waning.”