SCIENCE.ORG – A groundbreaking epidemiological study has produced the most compelling evidence yet that exposure to the chemical solvent trichloroethylene (TCE)—common in soil and groundwater—increases the risk of developing Parkinson’s disease.
The movement disorder afflicts about 1 million Americans, and is likely the fastest growing neurodegenerative disease in the world; its global prevalence has doubled in the past 25 years.
The report, published today in JAMA Neurology, involved examining the medical records of tens of thousands of Marine Corps and Navy veterans who trained at Marine Corps Base Camp Lejeune in North Carolina from 1975 to 1985.
Those exposed there to water heavily contaminated with TCE had a 70% higher risk of developing Parkinson’s disease decades later compared with similar veterans who trained elsewhere.
The Camp Lejeune contingent also had higher rates of symptoms such as erectile dysfunction and loss of smell that are early harbingers of Parkinson’s, which causes tremors; problems with moving, speaking, and balance; and in many cases dementia. Swallowing difficulties often lead to death from pneumonia.
About 90% of Parkinson’s cases can’t be explained by genetics, but there have been hints that exposure to TCE may trigger it. The new study, led by researchers at the University of California, San Francisco (UCSF), represents by far the strongest environmental link between TCE and the disease.
Until now, the entire epidemiological literature included fewer than 20 people who developed Parkinson’s after TCE exposure.
The Camp Lejeune analysis “is exceptionally important,” says Briana De Miranda, a neurotoxicologist at the University of Alabama at Birmingham who studies TCE’s pathological impacts in the brains of rats. “It gives us an extremely large population to assess a risk factor in a very carefully designed epidemiological study.”
“We had suspicions, but this is the evidence,” agrees Gary Miller, a neurotoxicologist who studies Parkinson’s disease at Columbia University. “It’s very compelling.”
TCE is a colorless liquid that readily crosses biological membranes …