Contaminated Drinking Water, Environmental Factors May Increase Risk of Parkinson Disease

Samuel M. Goldman, MD, MPH

Results from a recently published study in JAMA Neurology showed that the risk of Parkinson disease (PD) was increased in veterans formerly stationed at Camp Lejeune, a Marine Corps base where water was contaminated with trichloroethylene (TCE) and other volatile organic compounds (VOCs). These findings suggest a potential association between exposure to TCE and other VOCs in contaminated water and the development of PD.¹

All told, the crude prevalence rate of PD was higher in Camp Lejeune veterans compared with those stationed at Camp Pendleton (0.33% vs 0.21%), a base with uncontaminated water, resulting in a 70% higher rate (OR, 1.70; 95% CI, 1.39-2.07). Notably, residence at Camp Lejeune was associated with a statistically significant increased risk of prodromal risk scores (internal: OR, 1.14 [95% CI, 1.03-1.26]; Movement Disorders Society: OR, 1.18 [95% CI, 1.06-1.32]) and an overall increased PD risk of 14% to 20% among men.

Lead author Samuel M. Goldman, MD, MPH, clinical professor at the University of California, San Francisco in the Division of Occupational & Environmental Medicine and the Department of Neurology, and colleagues wrote, “Our findings suggest that exposure to TCE and other VOCs in contaminated drinking water may be an important risk factor for PD, and that prodromal features of PD may be more common in individuals with such exposure."¹

The retrospective cohort study analyzed data from the Veterans Health Administration (VHA) databases, including 340,489 service members who were stationed at Marine Corps Base Camp Lejeune or other Marine Corps bases between 1975 and 1985. The primary outcome of interest was PD, while assessing for potential confounding variables such as age, sex, race/ethnicity, military rank, and smoking status.

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There were 84,824 veterans from Camp Lejeune (49.3%; mean [SD] age, 59.6 [4.4] years) and 73,298 veterans from Camp Pendleton (43.5%; mean [SD] age, 59.8 [4.6] years). The demographic characteristics were similar between both Camp Lejeune (women, 5.3%; men, 94.7%; mean attained age of 59.64 [SD, 4.43] years; Black, 29.7%; Hispanic, 6.0%; White, 67.6%; other race and ethnicity, 2.7%) and Camp Pendleton (women, 3.8%, men, 96.2%; mean age, 59.80 [SD, 4.62] years; Black, 23.4%; Hispanic, 9.4%; White, 71.1%; other race and ethnicity, 5.5%). PD risk was substantially lower among Black veterans (OR, 0.33; 95% CI, 0.25-0.45) and ever-smokers (OR, 0.49; 95% CI, 0.40-0.61) as well as Hispanic (OR, 0.68; 95% CI, 0.45-1.02) and female (OR, 0.79; 95% CI, 0.49-1.28) veterans.

"The association between Camp Lejeune service and PD was stronger in men than in women, which is consistent with previous studies suggesting that men may be more susceptible to environmental toxins," Goldman et al noted.¹

In the note of the limitations, researchers only had diagnostic information for participants who received health care through the VHA or Medicare, which could have led to bias in the Camp Lejeune veterans. Also, researchers could not be certain that everyone who resided at Camp Lejeune in the study period was exposed to biologically meaningful levels of contaminants. Also, exposure to environmental toxicants outside the camps could have occurred and although TCE was the VOC present in the Camp Lejeune water supply, the water also contained other compounds which could have contributed to the associations observed.

Gold et al wrote, "Our study highlights the importance of identifying environmental risk factors for PD, particularly those that are modifiable, such as exposure to TCE and other VOCs. Further research is needed to confirm our findings and to evaluate potential interventions to reduce exposure to these compounds."¹

TCE was first synthesized in 1864 and was used for military, industrial, and commercial purposes, including degreasing metal, decaffeinating coffee, and dry-cleaning clothes. PD is one out of the many conditions associated with the widely used chemical.² In 2012, Goldman et al conducted a study cohort of twins from World War II and observed that occupational or hobby exposure to TCE was associated with a 500% increased risk of PD.³

REFERENCES
1. Goldman SM, Weaver FM, Stroupe KT, et al. Risk of Parkinson Disease Among Service Members at Marine Corps Base Camp Lejeune. JAMA Neurol. 2023;e231168. doi:10.1001/jamaneurol.2023.1168
2. Dorsey ER, Greenamyre JT, Willis AW. The Water, the Air, the Marines-Camp Lejeune, Trichloroethylene, and Parkinson Disease. JAMA Neurol. 2023;10.1001/jamaneurol.2023.1174. doi:10.1001/jamaneurol.2023.1174
3. Goldman SM, Quinlan PJ, Ross GW, et al. Solvent exposures and Parkinson disease risk in twins. Ann Neurol. 2012;71(6):776-784. doi:10.1002/ana.22629