Parkinson’s disease (PD) is a debilitating neurodegenerative disorder affecting an estimated 10 million people worldwide, with numbers projected to increase as the global population ages. The disease is characterized by a multitude of symptoms, including resting tremors, rigidity, bradykinesia (slowness of movement), postural instability, and various non-motor symptoms such as sleep disturbances, cognitive impairment, and mood disorders. The precise cause of PD remains unknown, but recent studies have suggested potential environmental triggers.
Trichloroethylene (TCE) is one such environmental factor gaining attention. This industrial solvent, used since the 1920s, is employed in metal degreasing, coffee decaffeination, and dry cleaning of clothes. It is found in many consumer products such as paint removers, adhesive and spot removers, and rug-cleaning fluids. Yet, TCE doesn’t stay in these products; it can leach into groundwater and soil due to poor disposal practices and spills, contaminating the environment and our water supplies.
Several studies have linked TCE exposure to a host of health issues including cancer, miscarriages, neural tube defects, congenital heart disease, autoimmune disorders, and notably, Parkinson’s disease.
Recent Findings: A Connection Between TCE and Parkinson’s
An analysis of data from 158,000 military veterans has highlighted an alarming correlation between TCE exposure and an increased risk of PD. Personnel stationed at Marine Corps Base Camp Lejeune in North Carolina between 1975 and 1985, where drinking water was contaminated with TCE, faced a 70% increased risk of Parkinson’s disease compared to those at Camp Pendleton, a large California base with less TCE exposure.
The exposure to TCE occurred when Marines were, on average, 20 years old, with Parkinson’s diagnoses surfacing an average of 34 years later. Furthermore, former residents of Camp Lejeune displayed a higher prevalence of early Parkinson’s signs such as tremors, suggesting that the disease might still be undiagnosed in some veterans.
“This is unquestionably the largest human epidemiological study attributing Parkinson’s disease to trichloroethylene,” said Samuel Goldman, MD, MPH, from the University of California San Francisco. “It validates our presumption that exposure to TCE is a risk determinant for Parkinson’s disease.”
Goldman further revealed that the study identified 279 individuals from Lejeune diagnosed with Parkinson’s disease, a significant number when compared to the approximately 20 cases linked to TCE exposure in previous reports and studies.
Notably, this is the first study to investigate environmental TCE exposures as opposed to workplace-related exposures. This is a critical point since nearly 1 million people lived and worked at Camp Lejeune from 1953 to 1987, during which the water supply was contaminated.
During the years 1975 to 1985, the median monthly TCE level in the Camp Lejeune water supply was 70 times the acceptable limit. Wells supplying water to the base were shut down in the mid-1980s following the discovery of contamination from various sources, primarily TCE and perchloroethylene (PCE).
Health records of 172,128 Marines and Navy personnel who resided at Camp Lejeune for a minimum of 3 months during this period were reviewed and compared to those of 168,361 personnel at Camp Pendleton. The demographic profiles were similar across both groups.
The follow-up period stretched from January 1997 to February 2021. Parkinson’s disease diagnostic codes and prodromal disease indicators in the Veterans Health Administration (VHA) and Medicare databases were included. Parkinson’s diagnoses were verified by medical record review.
The average age at follow-up was 59.7. In total, 430 veterans received a Parkinson’s diagnosis at an average age of 54.2 — 279 from Camp Lejeune (crude prevalence 0.33%) and 151 from Camp Pendleton (crude prevalence 0.21%). No surplus risk was observed for other types of neurodegenerative parkinsonism.
Despite these findings, it’s important to note that exposure to TCE was variable and inferred in this study, but not definitively confirmed. Moreover, the study focused on Marines who received care through the VHA or Medicare, excluding spouses, dependents, and the large civilian population who worked at the base.
Still, these limitations may underestimate the actual risk associated with these toxicants and the extent of the health problems related to their exposure at Camp Lejeune. “It’s important to continue studying them going forward,” Goldman pointed out. “TCE is still widely used in industry, and shockingly, you can easily buy it on Amazon.”
This study underscores the potential dangers posed by environmental toxins like TCE, underlining the importance of proper disposal and contamination prevention. With Parkinson’s disease prevalence on the rise, it’s more crucial than ever to understand and mitigate these environmental risk factors.
