Common Chemical Strongly Linked to Parkinson's

Service members stationed at Camp Lejeune, where water was contaminated, had a 70 percent greater risk of developing the movement disorder, new study finds

Will Sullivan

A study of military veterans has shown the strongest evidence yet that the widespread chemical trichloroethylene (TCE)—used in spot removers, office products and dry-cleaning—is linked to Parkinson's disease.

The research focused on service members who were stationed at Camp Lejeune in North Carolina between 1975 and 1985, when levels of TCE in the base's water reached 70 times higher than the Environmental Protection Agency's limit. After accounting for demographic factors, Camp Lejeune veterans were 70 percent more likely to develop the movement disorder than service members stationed at Camp Pendleton in California, where the water was uncontaminated.

The large study, published last week in the journal JAMA Neurology, adds to a handful of smaller, earlier papers that found a link between TCE and Parkinson's.

"We had suspicions, but this is the evidence," Gary Miller, a neurotoxicologist studying Parkinson's at Columbia University who wasn't involved in the study, tells Science's Meredith Wadman. "It's very compelling."

Though the study focused on veterans, it's not just former Camp Lejeune residents who have faced TCE exposure. "Almost everyone reading your story likely lives near a site contaminated with TCE," Ray Dorsey, a neurologist at the University of Rochester who has studied the link between TCE and Parkinson's but was not involved with the new research, tells CNN's Jen Christensen. "So, this is a real concern."

TCE, which can be in liquid or vapor form, has been commonly used since the 1920s, including as an inhaled surgical anesthetic and in several cleaning products. Today, it's primarily used in making refrigerants and degreasing metal equipment, according to the National Cancer Institute. But over time, TCE has built up in the environment at thousands of sites countrywide. The chemical breaks down slowly and can be detected in the air, water and soil. It's also found in one-third of U.S. drinking water, per Science.

"TCE is still a very commonly used chemical in the United States and worldwide," Samuel Goldman, a co-author of the study and an epidemiologist at the University of California, San Francisco, tells the Indo-Asian News Service. "Its production has been increasing over the past several years and is widely available online."

Earlier studies in rodents have shown that chronic TCE exposure causes brain damage associated with Parkinson's. A small study of twins also found a link between TCE and the movement disorder, per the paper. And research published in March urged scientists to further study this connection, the Los Angeles Times’ Tony Briscoe wrote at the time.

Parkinson's is a brain disorder that causes uncontrollable movements, balance and coordination problems, and it can eventually lead to difficulties with memory, walking and talking, per the National Institute on Aging. It currently affects more than ten million people worldwide, but that number is increasing, according to CNN.

The new study looked at more than 340,000 service members who were stationed at one of the two bases for at least three months during the ten-year window. To find out how many people later developed Parkinson's, the team went through medical records in Veterans Health Administration and Medicare databases that spanned January 1997 through February 2021. They found that 0.33 percent of the service members from Camp Lejeune had developed Parkinson's, compared to 0.21 percent of those from Camp Pendleton.

One drawback of the study, however, is that a recent government policy might have encouraged more people who had been stationed at Camp Lejeune to seek health care through the Department of Veterans Affairs (VA). Camp Lejeune veterans with certain cancers and other conditions could automatically qualify for VA benefits and health coverage beginning in 2017, per the Wall Street Journal's Ben Kesling. That could have led to people with Parkinson's from Camp Lejeune being overrepresented.

Still, it's possible that not every person stationed at Camp Lejeune came into contact with TCE, which could mean the link between the chemical and Parkinson's is stronger than what the study found, Science notes.

The Camp Lejeune drinking water was contaminated with TCE and other chemicals from 1953 to 1987, per the study, due to leakage from underground storage tanks, industrial spills, waste disposal sites and a dry-cleaning business. Exposure to the chemicals in the drinking water at Camp Lejeune during this period has been linked to leukemia, aplastic anemia (bone marrow failure), bladder cancer, liver cancer, kidney cancer, multiple myeloma (a cancer of white blood cells), non-Hodgkin's lymphoma and Parkinson's, per the VA.

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Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.