A chemical used to degrease industrial parts that was also used as a surgical anesthetic until the 1970s may increase the risk for Parkinson’s disease, researchers report.

Their new study found that two years of heavy exposure to the liquid chemical TCE may boost Parkinson’s risk by 70%.

TCE, or trichloroethylene, lingers in the air, water and soil. It has been linked to certain cancers.

For the study, researchers compared Parkinson’s diagnoses in about 160,000 U.S. Navy and Marine veterans.

A little more than half came from Camp Lejeune, a Marine base in Jacksonville, N.C., where TCE used to degrease military equipment fouled the water.

Between 1974 and 1985, service members spent at least three months at Camp Lejeune or Camp Pendleton in California.

TCE levels in the water at Camp Lejeune were 70 times higher than maximum safety level. Water at Camp Pendleton was not contaminated.

Data included follow-up health information from 1997 to 2021, by which time the veterans might have been expected to develop Parkinson’s disease.

In all, 430 vets were diagnosed with Parkinson’s. The risk for those who spent time at Lejeune was 70% higher than that for Camp Pendleton vets.

On average, service members were stationed at their camps for about two years, beginning at age 20. They were diagnosed with Parkinson’s at an average age of 54 for Lejeune and 53 for Pendleton, decades after their exposure.

TCE can persist for decades in the soil or groundwater. It is now used mostly as a degreaser, but has been used for industrial and commercial purposes for nearly 100 years. It was banned as a surgical anesthetic in 1977.

To degrease parts, it is heated in a tank to create a vapor that dissolves grease. The chemical then enters the atmosphere.

The risk of TCE exposure goes beyond military personnel. Civilians are also at risk, said first author Dr. Samuel Goldman, of the University of California, San Francisco Division of Occupational, Environmental and Climate Medicine and the San Francisco VA Medical Center.

Between 9% and 34% of U.S. water supplies contain measurable amounts of TCE.

“TCE is still a very commonly used chemical in the United States and throughout the world,” Goldman said in a university news release. “Its production has been increasing over the past several years and it is widely available online.”

He said there is no easy way to know if you have been exposed to it unless you worked with it directly.

“Many of us have detectable levels of TCE in our bodies, but it gets metabolized and excreted very quickly, so blood and urine tests only reflect very recent exposure,” Goldman said.

The study also found that the Lejeune vets had a higher rate of prodromal Parkinson’s, which is suggestive of the disease but does not meet diagnostic criteria.

“Loss of sense of smell, a sleep disorder known as RBD, anxiety, depression and constipation can be early signs of Parkinson’s, but only a very small fraction of people with them will develop it,” said senior author Dr. Caroline Tanner, of the UCSF Weill Institute for Neurosciences and the San Francisco VA.

“The risk of developing Parkinson’s in the future can be estimated using a risk score based on these symptoms,” Tanner said in the release. “The Lejeune veterans had higher risk scores than the Pendleton veterans, suggesting that they are more likely to develop Parkinson’s in the future.”

The findings were published May 15 in JAMA Neurology. The U.S. Department of Veterans Affairs supported the study.

More information

The U.S. National Library of Medicine has more on Parkinson’s disease.

SOURCE: University of California, San Francisco, news release, May 15, 2023