The difference may have been in the Camp Lejeune vets’ exposure to a chemical known as trichloroethylene (TCE), a ubiquitous environmental contaminant, the researchers warn. And the risk of developing this disorder of the nervous system may be higher for millions more people.
The number of people with Parkinson’s disease has been increasing around the world. Some estimates suggest that nearly 20 million people could have it by 2040.
Scientists aren’t exactly sure what causes Parkinson’s. Age is a factor, and the growth of the disorder is in part related to the graying population, scientists believe. But some also say that exposure to chemicals like TCE is helping drive the growth.
Dr. Ray Dorsey, the David M. Levy professor of neurology at the University of Rochester, said he believes that TCE may be one of the most important causes of Parkinson’s disease, especially in suburban and urban environments, in the United States.
Between 4.5% and 18% of the drinking water supply sources in the US that are tested on a yearly basis by EPA have some TCE contamination, according to the Agency for Toxic Substances and Disease Registry.
Dorsey, who was not involved in the new study but has conducted similar research, said it is important to note that the Marines in this study were exposed to TCE for a relatively short period of time.
“There could be many more Marines that developed Parkinson’s disease,” he said. “Almost everyone reading your story likely lives near a site contaminated with TCE. So this is a real concern.”
TCE is a colorless volatile organic compound that was widely used in industry as a cleaning agent and a degreaser, mainly for metal. It’s also used in the manufacturing of some refrigerants and can be found in paints, sealants, coatings and some automobile products like brake cleaners.
TCE was synthesized in 1864, but it wasn’t until the 1920s that it became one of the most widely used solvents in industry. It started falling out of fashion in the 1960s after scientists began to suspect that exposure was harmful to human health, but it is still used in some industrial applications today.
Because it was so widely used for the past 100 years, TCE has been found in thousands of water sources and properties around the world. The chemical can hang in the air and remains in groundwater for long periods of time, according to the US Centers for Disease Control and Prevention.
In January, the US Environmental Protection Agency finalized a revision to the Toxic Substances Control Act risk determination for TCE, saying it presents an unreasonable risk to human health.
Most people are exposed to TCE through drinking contaminated groundwater, but exposure can also come through breathing it in as it is released from the water or from the processes that use TCE.
Exposure can raise the risk of cancer, affect the liver and cause damage to the nervous system and brain, according to the EPA.
This new study, published Monday in the journal JAMA Neurology, focused on the link between TCE and Parkinson’s. The study was funded by the US Department of Veterans Affairs, but it did not design or conduct the research.
The researchers looked at the health records of 340,000 servicemembers who were stationed at Marine Corps Base Camp Lejeune, North Carolina, from 1975 through 1985, a time in which the water at the base was known to be contaminated with TCE and other volatile organic compounds.
Tests have showed that levels in the water during the studied time period were 70-fold more than the permissible amount, according to the new study. Thousands of lawsuits have been filed against the US government over TCE.
The researchers compared Camp Lejeune records to data from Camp Pendleton, California. They then followed up with the same group of veterans, looking at their health records from January 1, 1997, until February 17, 2021, to see who developed Parkinson’s or other diseases.
The study found that the risk of Parkinson’s disease was 70% higher in veterans who were stationed at Camp Lejeune than in those stationed at Camp Pendleton.
The research had some limitations, including that exposure would be variable depending on how much people used the water on the base and based on where they worked and lived on-site. The study is also based on claims data, rather than on a clinical diagnosis. The data captures the health information only of veterans who saw a doctor through the VA or Medicare. And the comparison base, Camp Pendleton, also had some TCE contamination, but it was at a lower level.
The new research builds on a growing body of scientific evidence suggesting a link between TCE exposure and Parkinson’s. Dorsey conducted a small study of twin pairs that found that exposure to TCE was previously associated with a sixfold increased risk of Parkinson’s disease, and a 2012 study says TCE exposure was associated with a 500% higher risk of Parkinson’s disease. Animal studies have shown a similar risk.
In a statement, the US Department of Veterans Affairs said it “encourages all Veterans who served for at least 30 days total at Camp Lejeune between August 1, 1953, and December 31, 1987 – and their family members – to apply for the care and benefits they deserve at VA.gov/CampLejeune.
“Parkinson’s disease is a presumptive condition for Veterans who were exposed to the contaminated water at Camp Lejeune. This means that when eligible Veterans apply for benefits, they do not need to prove that their service caused their Parkinson’s disease; instead, VA automatically assumes service-connection for these Veterans and provides benefits accordingly.
“Additionally, thanks to the PACT Act, Veterans and their families can now file lawsuits for harm caused by exposure to contaminated water at Camp Lejeune. More information on this process can be found here.”
The latest study adds solid evidence that more needs to be done to prevent Parkinson’s by limiting exposure to TCE, said Dorsey, co-author of an editorial published alongside the study in JAMA Neurology. Most countries in Western Europe ban TCE, as have New York, Pennsylvania and Minnesota.
“It’s time for us to, one, ban the chemical; two, clean up the contaminated sites; three, remediate them so people are protected from further exposure to these chemicals; and four, notify people who live near these contaminated sites,” Dorsey said. “It’s still widely permitted in most states, and clearly, it shouldn’t be.”