Parkinson's Linked With Industrial Solvents in Drinking Water

Exposure to the industrial solvent trichloroethylene (TCE) and other volatile organic compounds in drinking water raised the risk of Parkinson's disease decades later, an analysis of 158,000 military veterans showed.

Personnel who lived at Marine Corps Base Camp Lejeune in North Carolina from 1975 to 1985 had a 70% higher risk of Parkinson's disease (OR 1.70, 95% CI 1.39-2.07, P<0.001) compared with those who lived at Camp Pendleton, a large California base, reported Samuel Goldman, MD, MPH, of the University of California San Francisco and the San Francisco Veterans Affairs Medical Center, and co-authors.

Exposure occurred when Marines were an average of age 20, the researchers wrote in JAMA Neurology. Parkinson's diagnoses emerged at Camp Lejeune an average of 34 years later.

Former Camp Lejeune residents also had a higher prevalence of prodromal features like tremor, suggesting that for some veterans, Parkinson's might not yet be diagnosed.

Trichloroethylene has been used since the 1920s to de-grease metal, decaffeinate coffee, and dry clean clothes. It has been linked with cancer, miscarriages, neural tube defects, congenital heart disease, autoimmune disorders, and Parkinson's disease in earlier research.

"This is by far the largest human epidemiological study to implicate trichloroethylene as a cause of Parkinson's disease," Goldman told MedPage Today. "It confirms what we suspected -- namely, that TCE exposure is a risk factor for Parkinson's disease."

"We identified 279 individuals from Lejeune with Parkinson's disease," Goldman continued. "In comparison, all prior case reports and our 2012 study in twins had identified a total of approximately 20 cases linked to TCE. So, we were basing our suspicions on a really small number of observations."

"Also, this is the first study that looked at environmental TCE exposures," he said. "All prior studies had been occupational exposures. This is important because up to 1 million people lived and worked at Camp Lejeune during the period from 1953 to 1987 when the water was contaminated."

From 1975 to 1985, the median monthly level of TCE in Camp Lejeune drinking water was 70 times higher than the permissible level. Wells providing water to the base were taken offline in the mid-1980s after contamination from underground storage tanks, industrial spills, and waste disposal sites (largely TCE) and an off-base dry cleaning business (largely perchloroethylene, or PCE) was discovered.

Goldman and co-authors evaluated health records for 172,128 Marines and Navy personnel who lived at Camp Lejeune for at least 3 months from 1975 to 1985, comparing them with 168,361 Camp Pendleton personnel. Demographics were similar in the two groups.

Follow-up was from January 1997 until February 2021 and included diagnostic codes for Parkinson's disease and indicators of prodromal disease in Veterans Health Administration (VHA) and Medicare databases. Parkinson's diagnoses were confirmed by medical record review.

Mean age at follow-up was 59.7. Overall, 430 veterans had a Parkinson's diagnosis at a mean age of 54.2 -- 279 from Camp Lejeune (crude prevalence 0.33%) and 151 from Camp Pendleton (crude prevalence 0.21%). No excess risk was found for other forms of neurodegenerative parkinsonism, including corticobasal degeneration, dementia with Lewy bodies, multiple system atrophy, or progressive supranuclear palsy.

In models restricted to participants without Parkinson's or other parkinsonism, Camp Lejeune residents had a significantly increased risk of prodromal Parkinson's diagnoses including anxiety, tremor, and erectile dysfunction (P<0.001 for all).

TCE exposure was most likely variable and was inferred in this study but was not certain, noted E. Ray Dorsey, MD, of the University of Rochester Medical Center in New York, and co-authors, in an accompanying editorial. Parkinson's diagnoses were based on claims data and were limited to Marines who received care through the VHA or Medicare.

The study excluded spouses, dependents, and the large civilian population who worked at the base, the editorialists added. Camp Pendleton, like many military bases, also had TCE and PCE in the water supply, but levels were lower than at Camp Lejeune.

"Importantly, these limitations may underestimate the risk associated with these toxicants and the magnitude of the health problems associated with their exposure at Camp Lejeune," Dorsey and colleagues observed.

In December 2022, the Environmental Protection Agency found that PCE posed an unreasonable risk to human health; in January 2023, it reached the same conclusion for TCE. Also in 2022, President Biden signed the Promise to Address Comprehensive Toxics (PACT) Act, which included the Camp Lejeune Justice Act of 2022, allowing people harmed by TCE, PCE, benzene, and other toxicants at Camp Lejeune to seek compensation from the U.S. government.

"The Lejeune cohort that we studied is still quite young in terms of their Parkinson's disease risk -- their mean age is about 60 -- so it's important to continue to study them going forward," Goldman noted. "TCE is still widely used in industry, and shockingly, you can easily buy it on Amazon."

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