This may be the cause of the world’s fastest-growing brain condition, Parkinson’s disease.

Recent research has suggested that trichloroethylene (TCE), a commonly used chemical for the past century, may be contributing to the rapid growth of Parkinson’s disease worldwide. TCE has been employed in a variety of industries, from decaffeinating coffee to degreasing metal and dry cleaning clothes. However, the chemical has also been identified as a contaminant in numerous locations, including the Marine Corps base Camp Lejeune, 15 Superfund sites in Silicon Valley, and up to one-third of the groundwater in the United States.

TCE has been linked to cancer, miscarriages, and congenital heart disease, and now a 500 percent increased risk of Parkinson’s disease. The alarming findings have raised concerns over the potential health risks associated with the use and disposal of TCE. As the world grapples with the ongoing pandemic, it is crucial that we remain vigilant to other public health crises that could be exacerbated by industrial chemicals like TCE.

The University of Rochester Medical Center’s (URMC) neurologists Ray Dorsey, MD, Ruth Schneider, MD, and Karl Kieburtz, MD, together with an international team of researchers, make this claim in a paper published in the Journal of Parkinson’s Disease. In the article, they discuss the chemical’s widespread use, the evidence that links it to Parkinson’s, and they profile seven people who either developed Parkinson’s disease after working with the chemical or after being exposed to it in the environment, including a former NBA basketball player, a Navy captain, and a late U.S. senator.

TCE was a widely used solvent that was used in many industrial, consumer, military, and medical settings. It was used to remove paint, fix typewriting mistakes, clean engines, and put patients to sleep, among other things. It was used the most in the U.S. in the 1970s, when more than 600 million pounds, or two pounds for each American, were made each year. An estimated ten million people in the United States worked with chemical or with other industrial solvents that were quite similar. TCE is still used in the United States for spot dry cleaning and degreasing metal, although its domestic usage has decreased since then.

Trichloroethylene (TCE) is a pervasive environmental contaminant that has been found in countless sites across the United States. Half of the most toxic sites identified by the Environmental Protection Agency’s Superfund program contain TCE. In California’s Silicon Valley alone, fifteen Superfund sites have been identified as having TCE contamination. The chemical was heavily used in the region for cleaning electronics and computer chips. Military bases are also affected by TCE, including the infamous Camp Lejeune in North Carolina. Between the 1950s and 1980s, an estimated one million Marines, their families, and civilian workers who lived or worked at the base were exposed to unsafe levels of TCE and perchloroethylene (PCE), a similar chemical compound. In some cases, the levels of these chemicals in the drinking water were up to 280 times higher than safe levels.

More than half a century ago, case studies hinted at a potential link between Parkinson’s disease and TCE. Since then, experiments with mice and rats have demonstrated that TCE can easily penetrate the brain and bodily tissues, and at high doses, can harm the mitochondria, which are responsible for producing energy within cells. Furthermore, TCE has been found to cause the selective destruction of nerve cells that produce dopamine in animal models, which is a defining characteristic of Parkinson’s disease in humans.

Those who have direct contact with TCE had a higher chance of getting Parkinson’s. Millions more people, the authors caution, come into contact with the chemical inadvertently via polluted groundwater, indoor air pollution, and outdoor air.

The substance has the potential to pollute groundwater and soil, resulting in subterranean rivers or plumes that may travel over great distances and migrate over time. One such plume linked to a New York City aerospace firm is nearly four miles long and two miles broad, and it has tainted the water supply for millions. The same is true of others; you may find them in Shanghai, China, or Newport Beach, California.

Despite its dangers to water, the flammable TCE may easily evaporate and infiltrate people’s homes, educational institutions, and places of employment, often unnoticed. Millions of people now who live, study and work close to old industrial, military, and dry cleaning facilities are probably being exposed to harmful indoor air as a result of this vapor intrusion. In the 1980s, radon was found to evaporate from the ground, get into homes, and raise the risk of lung cancer. This was the first time that vapor intrusion was talked about. Nowadays, millions of houses get radon tested, but few are TCE tested, which causes cancer.

This paper focuses on seven different people whose Parkinson’s disease may have been caused by exposure to the chemical TCE. These people’s tales demonstrate the difficulties in making the case against chemicals, even if the data connecting TCE exposure to Parkinson’s disease in these people is just circumstantial. In these cases, Parkinson’s symptoms often don’t show up until many years after the person was exposed to TCE.

NBA star Brian Grant, who had a 12-year career before being diagnosed with Parkinson’s at age 36, is one of the featured case studies. When Grant was three years old and his father, a Marine at the time, was stationed at Camp Lejeune, it’s possible that he was exposed to TCE. Grant has set up a charity to encourage and aid others dealing with the illness.

While serving as a young Navy captain at Camp Lejeune, Amy Lindberg was also exposed to tainted drinking water and was ultimately given a Parkinson’s disease diagnosis 30 years later. The article describes further people who were exposed as a consequence of living near a contaminated site or dealing with the substance, including the late U.S. Senator Johnny Isakson, who resigned from office in 2015 after receiving a Parkinson’s diagnosis. About fifty years ago, he was a member of the Georgia Air National Guard, where TCE was utilized for aircraft degreasing.

The authors write that “for more than 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.”

To address the harm that TCE poses to the public’s health, the authors recommend a number of steps. They point out that polluted sites can be effectively cleaned up, and vapor remediation technologies, like those used for radon, may reduce interior air exposure. Yet, the cleaning and containment procedure has to be sped up since the United States alone is home to thousands of polluted sites.

To understand how TCE affects Parkinson’s and other disorders, they call for greater study. TCE levels in soil, groundwater, drinking water, and outdoor and indoor air need to be monitored more closely, and people who live and work close to contaminated areas need to be notified of this material.

The authors also urge the U.S. to finally stop using PCE and TCE, which are still commonly used in dry cleaning and vapor degreasing, respectively. Despite the EPA’s conclusion that the chemicals pose “an unreasonable risk to human health” as recently as 2022, only two states—Minnesota and New York—have banned TCE.

Source: 10.3233/JPD-225047

Image Credit: Donald Miralle/Getty Images