People living near dry cleaners may have a higher risk of developing Parkinson's disease according to a new nationwide study led by researchers at Barrow Neurological Institute in Phoenix.
The study was recently published in npj Parkinson's Disease as an unedited manuscript to provide early access to the findings. The final version will be published following further editorial review.
The analysis examined Medicare records from nearly 19 million older adults in the United States. Researchers found that people living within approximately 500 feet of a dry cleaner had a 14 percent greater risk of developing Parkinson's disease compared to those living further away. The association gradually declined with increasing distance, suggesting the closer someone lived to a dry cleaner, the stronger the link between proximity and Parkinson's disease, even after accounting for other risk factors.
"This study adds to growing evidence that environmental exposures may play an important role in Parkinson's disease," said Brad Racette, MD, Chairman of Neurology and Senior Vice President of Barrow Neurological Institute, and senior author of the study. "Identifying those exposures is an important step toward understanding how we might reduce the burden of this disease in the future."
Researchers say the findings add to growing evidence linking long-term exposure to chlorinated solvents, including trichlorethylene (TCE) and perchloroethylene (PCE), with Parkinson's disease. For decades, these chemicals were used by dry cleaners as powerful cleaning agents to dissolve grease and stains from clothing without water. While TCE was largely phased out of the dry-cleaning industry decades ago, many facilities switched to PCE, which can break down into TCE underground. As a result, both chemicals can remain in contaminated soil and ground water for years, even after a dry cleaner has closed.
The researchers found the strongest association among people with Parkinson's disease who had walking and balance problems, falls and cognitive impairment. This suggests environmental exposures may influence not only a person's likelihood of developing Parkinson's disease, but also the presenting symptoms.
Researchers also identified geographic regions where the association between living near dry cleaners and Parkinson's disease were strongest, including Southeastern Illinois, the Tennessee-Kentucky border, and Dallas, TX. The study authors speculate that these regional differences may reflect factors such as historical contamination, local geology or aging infrastructure that could influence environmental exposure. However, more research is needed to better understand why these differences exist.
While this study does not prove that solvent exposure from dry cleaners causes Parkinson's disease, the findings add to a growing body of evidence suggesting residential environmental exposures may play an important role in the disease and highlight the importance of continued research and environmental monitoring.
