Parkinson's: Could a common cleaning chemical cause the disease?

More than 8.5 million people worldwide have Parkinson's disease — a condition affecting the nervous system that causes movement issues, such as tremors, stiffened limbs, and cognitive problems.

Doctors still do not understand why Parkinson's occurs. However, the disease has been linked to low levels of dopamine and norepinephrine in the body. Additionally, people with certain risk factors, such as age and past traumatic brain injury, are more likely to develop the condition.

Additionally, researchers believe exposure to certain toxins, such as pesticides and air pollution.

Now researchers from the University of Rochester are adding additional evidence by finding a link between Parkinson's disease and a commonly-used chemical called trichloroethylene (TCE).

The study appears in the Journal of Parkinson's Disease.

TCE is a colorless liquid chemical that does not occur in nature. It is known to have a chloroform-like odor.

This chemical may be found in a variety of products and industries, including:

People can become exposed to TCE by using a product containing TCE or working in a factory where the chemical is present.

Additionally, TCE can leach into the water, air, and soil around where it is used or disposed of, contaminating what we breathe, eat, and drink.

Symptoms of exposure to high amounts of TCE include:

Previous studies link prolonged exposure to TCE to increased risk for kidney cancer, liver cancer, and non-Hodgkin lymphoma.

Dr. Ray Dorsey, a professor of neurology at the University of Rochester and lead author of this study, said he and his team decided to research a link between TCE and Parkinson's disease while preparing to write his book, Ending Parkinson's Disease.

"One of my colleagues and co-authors of this paper, Dr. Caroline Tanner, told me about TCE and Camp Lejeune," Dr. Dorsey told Medical News Today. "She and her colleague, Dr. Sam Goldman — another (study) co-author — had conducted a twin study showing that twins with an occupational or hobby exposure to TCE had a 500% increased risk of Parkinson's disease. The more I investigated the prevalence of TCE and its role in Parkinson's disease, the more I (found) with no end in sight."

He added:

"TCE is a known carcinogen — it causes cancer. It is also linked to miscarriages, neural tube defects (including babies born without brains), congenital heart disease, and multiple other medical disorders. It also has been around for 100 years and its toxicity has been known for at least 90."

For this study, Dr. Dorsey and his team conducted a literature review. They compiled seven case studies of individuals who developed Parkinson's disease after exposure to the chemical from either the workplace or the environment.

The case studies include NBA player Brian Grant who received a Parkinson's diagnosis at the age of 36. According to researchers, he was likely exposed to TCE as a child when his father was stationed at Camp Lejeune in North Carolina.

The camp's water-supply systems were found to be contaminated with TCE in the early 1980s.

The researchers also profiled a Navy captain who had served at Camp Lejeune and was diagnosed with Parkinson's 30 years after.

And the research team also spotlighted the late United States Senator Johnny Isakson, who served in the Georgia Air National Guard, which used TCE to degrease airplanes. Senator Isakson was diagnosed with Parkinson's disease in 2015.

"Currently, the world's literature on trichloroethylene and Parkinson's disease is limited to 26 studies based on a search on PubMed," Dr. Dorsey said. "Given the widespread use and pollution with TCE and perchloroethylene (PCE), widely used in dry cleaning, and the rise of Parkinson's disease, more research is needed. We call for that."

"The seven individuals add to the existing literature — the largest previous case series was three — and demonstrate the myriad of ways that individuals can be exposed to the chemical via work or the environment," he added. "Importantly, most are unaware because they never knew about the exposure and it occurred decades ago."

In order for people to lower their exposure to TCE, Dr. Dorsey stated at a societal level the U.S. should ban TCE and PCE.

"In January 2023, the EPA found that TCE ‘poses an unreasonable risk to human health’," he continued. "A month earlier, it concluded the same about PCE. We don't drive cars or fly airplanes from the 1920s, when commercial production of TCE began, because engineers have developed safer alternatives. Chemists can do the same."

"Second, we should notify the public, especially those who live near contaminated sites, contain them, and prevent the entry of these gases into homes, schools, and workplaces with relatively inexpensive remediation systems, akin to what is used for radon," Dr. Dorsey added.

MNT also spoke with Dr. Ariana Spentzos, Ph.D., Science and Policy Fellow at the Green Science Policy Institute, who was not involved in this study.

Dr. Spentzos said it is unsurprising that this study found a link between TCE exposure and Parkinson's disease. She explained:

"TCE has a number of known adverse health effects and several studies over the last few decades have suggested TCE exposure as a risk factor for Parkinson's disease even from exposures decades before disease onset. The Department of Labor has even issued guidance on workers’ compensation acknowledging a link between TCE exposure and Parkinson's."

For people looking to lessen their TCE exposure, Dr. Spentzos said most TCE exposure occurs through inhalation.

"Indoor air quality can be improved by increasing ventilation or using air filters with activated carbon, although more sophisticated systems used for radon mitigation are most recommended," she detailed. "Since up to 30% of drinking water in the U.S. may be contaminated with TCE, the easiest way to reduce TCE levels is to filter your drinking water with activated carbon filters. Whole-house water filter systems can help avoid additional exposure through bathing, dishwashing, or other household uses."

"Additionally, avoid using any TCE-containing consumer products," Dr. Spentzos added. "Check to make sure that any paint strippers, stain-removers, adhesives, degreasers, and sealants, among other products, do not contain TCE in the ingredients list."