MJFF-funded researchers Samuel Goldman, MD, MPH, and Caroline Tanner, MD, PhD, FAAN, have linked an increased risk of PD to occupational exposure to common solvents, including a particular six-fold risk to trichloroethylene (TCE).
For the study, published online November 14 in Annals of Neurology, the researchers interviewed 99 twin pairs in which one twin had PD while the other did not. The interviews focused on each individual’s work history and hobbies.
The researchers were probing for situations that would have exposed individuals to the solvents perchloroethylene (PERC), carbon tetrachloride (CCI4) — both commonly used dry cleaning agents — and TCE. TCE was banned by the Food and Drug Administration in 1977. It once was used in dry-cleaning solutions, adhesives, paints, carpet cleaners, as a metal degreaser and as an anesthetic, skin disinfectant, and coffee decaffeinating agent, among other uses. TCE is also the most common organic contaminant in groundwater, and is found in up to 30% of drinking water supplies across the United States. (In September, the Environmental Protection Agency announced that TCE was also carcinogenic.)
Several studies have linked an individual’s exposure to solvents with an increased risk of PD. But the Goldman Tanner study is the first to report population-based findings data on the relationship between TCE exposure and PD.
To date, no definitive cause for PD has been discovered, yet environmental factors may in fact trigger the disease and have long been the focus of intense interest among Parkinson’s researchers. MJFF has funded multiple studies into environmental factors believed to play a role in PD, including a portion of the work being carried out by Tanner and Goldman. Other studies include:
- A 2006 grant to the Harvard School of Public Health was the first large scale study to examine the possible links between chronic, low-dose exposure to pesticides and PD risk. Data showed that individuals reporting exposure to pesticides had a 70 percent higher incidence of PD than those who did not.
- This past May, a team of researchers headed by Dr. Brad Racette of Washington University in St. Louis reported final outcomes of their work investigating how exposure to metals might lead to a higher risk for PD. Racette’s team studied 600 welders across the world, finding that, according to Positron emission tomography (PET) scans, welders had an average 11.7 percent reduction in a marker of the chemical dopamine compared to those who did not weld (Dopamine is decreased in certain brain regions in people with PD).