There is a robust link between environmental exposure to the industrial solvent trichloroethylene (TCE) in drinking water and subsequent Parkinson's disease (PD) in marines attending Marine Corps Base Camp Lejeune in North Carolina.
In one of the best-documented, large-scale contaminations in US history, the drinking water at the marine corps base was contaminated with TCE and other volatile organic compounds from about 1953 until 1987.
The new study of more than 340,000 service members found the risk of PD was 70% higher in Marines stationed at Camp Lejeune in North Carolina during the years 1975 to 1985, compared with Marines stationed on the West Coast at Camp Pendleton in California.
"This is by far the largest study to look at the association of TCE and PD and the evidence is pretty strong," lead investigator Samuel M. Goldman, MD, MPH, with University of California San Francisco, told Medscape Medical News.
The link is supported by animal models that show that TCE can induce a neurodegenerative syndrome that is "very similar pathologically to what we see in PD," Goldman said.
The study was published online today in JAMA Neurology.
"Hundreds of Thousands" at Risk
At Camp Lejeune during the years 1975-1985, the period of maximal contamination, the estimated monthly median TCE level was more than 70-fold the US Environmental Protection Agency (EPA) maximum contaminant level. Maximum contaminant levels were also exceeded for perchloroethylene (PCE) and vinyl chloride.
Goldman and colleagues had health data on 158,122 veterans — 84,824 from Camp Lejeune and 73,298 from Camp Pendleton — who served for at least 3 months between 1975 and 1985, with follow up from January 1, 1997 to February 17, 2021.
Demographic characteristics were similar between the two groups; most were White men with an average age of 59 years.
A total of 430 veterans had PD: 279 from Camp Lejeune (prevalence, 0.33%) and 151 from Camp Pendleton (prevalence, 0.21%).
In multivariable models, Camp Lejeune veterans had a 70% higher risk for PD (odds ratio, 1.70; 95% CI, 1.39 - 2.07; P < .001).
"Remarkably," the researchers note, among veterans without PD, residence at Camp Lejeune was also associated with a significantly higher risk of having several well-established prodromal features of PD, including tremor, suggesting they may be in a prediagnostic phase of evolving PD pathology.
Importantly, they add, in addition to the exposed service members, "hundreds of thousands of family members and civilian workers exposed to contaminated water at Camp Lejeune may also be at increased risk of PD, cancers, and other health consequences. Continued prospective follow-up of this population is essential."
"An Unreasonable Risk"
The new study supports a prior, and much smaller, study by Goldman and colleagues showing TCE exposure was associated with a sixfold increased risk for PD, as reported by Medscape Medical News.
TCE is a ubiquitous environmental contaminant. The EPA Toxics Release Inventory (TRI) estimates 2.05 million pounds of TCE was released into the environment from industrial sites in 2017.
In an accompany editorial, E. Ray Dorsey, MD, with University of Rochester, New York and co-authors note the work of Goldman and colleagues "increases the certainty" that environmental exposure to TCE and the similar compound PCE "contribute importantly to the cause of the world's fastest-growing brain disease."
"These actions could lay the foundation for increased regulation and possibly a ban of these two chemicals that have contributed to immeasurable death and disability for generations," Dorsey and colleagues note.
"A US ban would be a step forward but would not address the tens of thousands of TCE/PCE-contaminated sites in the US and around the world or the rising global use of the toxic solvents," they add.
This research was supported by US Department of Veterans Affairs. Goldman reports no relevant financial relationships. Dorsey has received personal fees from the American Neurological Association, Elsevier, International Parkinson and Movement Disorder Society, Massachusetts Medical Society, Michael J. Fox Foundation, National Institutes of Health, National Multiple Sclerosis Society, Northwestern University, Patient-Centered Outcomes Research Institute, Stanford University, Sutter Health, Texas Neurological Society Honoraria, Abbott, AbbVie, Acadia, Acorda Therapeutics, Biogen, BioSensics, Boehringer Ingelheim, Caraway Therapeutics, CuraSen, DConsult2, Denali Therapeutics, Eli Lilly, Genentech, Health & Wellness Partners, HMP Education, Karger, KOL Groups, Life Sciences, Mediflix, Medrhythms, Merck, MJH Holdings, North American Center for Continuing Medical Education, Novartis, Otsuka, Praxis Medicine, Sanofi, Seelos Therapeutics, Spark Therapeutics, Springer Healthcare, Theravance Biopharmaceuticals, and WebMD.