Parkinson’s disease is a brain disorder that slowly damages a person’s ability to control movement.
Scientists have long known that genes can influence the disease, but growing evidence suggests that chemicals in the environment may also play an important role.
One chemical attracting attention is trichloroethylene, commonly called TCE. Researchers from the University of Rochester and other institutions have reported evidence linking exposure to this widely used industrial chemical with Parkinson’s disease.
Parkinson’s develops when certain brain cells gradually stop working and die. These cells make dopamine, a chemical that helps the brain control smooth and coordinated movement.
As dopamine levels fall, people may develop shaking, muscle stiffness, slower movement and problems with walking or balance. Parkinson’s can also cause symptoms that are less obvious, including sleep problems, loss of smell, constipation, depression and changes in thinking.
There is currently no cure, although medicines, exercise and other treatments can help control symptoms. Because Parkinson’s is becoming more common worldwide, researchers are increasingly interested in finding preventable causes that may contribute to the disease.
TCE has been used for many decades as a cleaning and degreasing chemical. It has been used to clean metal parts, remove stains and in other industrial processes, and historically it was also used in dry cleaning and some consumer applications.
The concern is that TCE does not always stay where it is used. It can enter soil and groundwater after spills or improper disposal, and the chemical can move from contaminated ground into the air inside buildings.
This means exposure is not limited to factory workers. People may potentially encounter TCE through polluted water or air, including in homes, workplaces and other buildings near contaminated areas.
Scientists have suspected a connection between TCE and Parkinson’s for decades. The researchers reviewed earlier studies, animal experiments and reports involving people who developed Parkinson’s after known or suspected exposure to the chemical.
One important piece of evidence came from previous research involving twins. That study found that people exposed to TCE had about five times the risk of developing Parkinson’s compared with people who had not been exposed, although the number of exposed participants was relatively small.
The researchers also described seven people with Parkinson’s who had histories suggesting substantial TCE exposure. Their experiences included workplace exposure as well as possible environmental exposure, showing how contact with the chemical can occur in very different settings.
Laboratory research provides another reason for concern. Studies in animals have suggested that TCE can damage the same type of dopamine-producing brain cells that are lost in Parkinson’s disease, although animal findings cannot by themselves prove what happens in humans.
The researchers stress that TCE exposure does not mean a person will develop Parkinson’s. The disease probably results from a complicated combination of age, genetics, lifestyle and environmental exposures, and much remains unknown about why one person develops it while another does not.
Still, TCE is especially important because exposure can potentially be reduced. Cleaning contaminated sites, improving monitoring of groundwater and indoor air, and limiting the use and release of harmful chemicals could reduce unnecessary exposure.
More large studies are needed to measure exactly how much TCE contributes to Parkinson’s risk. Researchers also want to better understand whether the timing, amount and length of exposure make a difference, especially because Parkinson’s may appear decades after contact with a harmful chemical.
The research, led by Dr. Ray Dorsey and colleagues, was published in the Journal of Parkinson’s Disease. The authors argue that the possible role of TCE deserves much more attention as scientists search for environmental factors that may be contributing to the worldwide rise in Parkinson’s disease.
If you care about Parkinson’s disease, please read studies that Vitamin B may slow down cognitive decline, and Mediterranean diet could help lower risk of Parkinson’s.
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