Nearly 90,000 people will be diagnosed with Parkinson’s Disease (PD) this year. Parkinson's is a neurodegenerative disease affecting the brain and causing unintended or uncontrollable movements such as shakiness, stiffness and difficulty in coordination and balance. The primary risk factor for PD is age, and the increase of the disease aligns with the growth of our aging population. But it’s not the only factor.

A common chemical used in dry cleaning — trichloroethylene (TCE) — is also likely contributing to the rise of PD, an international team of researchers believes.

It’s highly likely that millions of people encounter TCE on a daily basis — through outdoor air, contaminated ground water and indoor pollution. Minnesota and New York have already banned it.

Over the years, TCE has also been widely applied to remove paint, correct typewriting errors, decaffeinate coffee, degrease metal, clean engines and even anesthetize patients. That’s not all. “TCE is found in numerous military bases, including Camp Lejeune in North Carolina. From the 1950‘s to the 1980’s, a million Marines, their families and civilians that worked or resided at the base were exposed to drinking water levels of TCE and perchloroethylene (PCE), a close chemical cousin, that was up to 280 times above what is considered safe levels,” the authors said, in a statement.

TCE is in up to one third of our country’s ground water. Besides contributing to Parkinson’s, this common chemical is linked to miscarriages and congenital heart disease.

The connection between TCE and Parkinson’s was first investigated more than 50 years ago. Since then, numerous studies using mice and rats showed how TCE easily entered brain and body tissues. In some of these animal studies, researchers reported that TCE caused selective loss of dopamine-producing nerve cells, a hallmark of Parkinson’s in people.

In the current paper, published in the Journal of Parkinson’s Disease, the authors use case studies of seven individuals, including a former NBA basketball player, a U.S. Navy captain, a late U.S. Senator, who developed Parkinson’s disease either after likely working with TCE or being exposed to it in the environment. In some instances, decades passed between their exposure to TCE and the onset of Parkinson’s symptoms.

TCE is everywhere. It not only pollutes water and soil, it also evaporates and mixes into the air we breathe. As the authors say, it’s highly likely that millions of people encounter TCE on a daily basis — “unknowingly through outdoor air, contaminated ground water, and indoor pollution.”

In 2022, the U.S. Environmental Protect Agency declared TCE “an unreasonable risk to human health.” But considering the risk TCE poses, the authors of the paper say that that’s not enough. Not only do they believe we should limit the concentration at sites now heavily contaminated with the toxic chemical, they also suggest the groundwater, soil and air at places near dry cleaning and metal degreasing facilities be regularly monitored to ensure the safety of people nearby.

Minnesota and New York have already banned TCE; the paper’s authors want the federal government to do the same for the entire country.