For decades we've known that the cleaning solvent chemical trichloroethylene (TCE) is associated with a higher risk of Parkinson's disease, but the scope of the danger may be greater than we realized.
According to new research, even living close to a dry cleaning business could raise your risk of developing the condition.
In a nationwide analysis published in npj Parkinson's Disease, scientists found people who lived within 150 meters (500 ft, 0.1 miles) of dry cleaners faced up to 23 percent higher estimated risk of developing Parkinson's, compared with people living farther away at a distance of 6.4–8 kilometers (4–5 miles).
"This study adds to growing evidence that environmental exposures may play an important role in Parkinson's disease," says neurologist and senior author of the study Brad Racette from the Barrow Neurological Institute in Phoenix, Arizona.
"Identifying those exposures is an important step toward understanding how we might reduce the burden of this disease in the future."
The findings add to a growing body of research showing that where you live can shape your environmental exposures – and potentially your health and risk of disease.
Scientists have previously demonstrated that where you live is linked to dementia risk, and it may also affect how quickly you age, and how healthily you eat.
In terms of Parkinson's, known environmental risk factors include air pollution, microplastics exposure, and pesticides, among others.
These kinds of risk factors can mean that places that don't seem obviously hazardous may actually carry potential health risks we don't always recognize, due to the chemical conditions of their environment.
For example, a study published last year found that living near a golf course was associated with higher Parkinson's risk, likely owing to pesticide use on fairways and greens.
Some of the same researchers who made that discovery have now turned their attention to dry cleaners. They analyzed US Medicare records for over 19 million people aged 67 or older between 2016 and 2018, including about 180,000 people diagnosed with Parkinson's disease.
After accounting for age, sex, race, income, and other potentially confounding factors, the researchers found people who lived within about 150 meters of a dry cleaner faced an overall 14 percent higher estimated risk of Parkinson's compared to people living 6.4–8 kilometers away.
This estimated risk increased to 23 percent higher for Parkinson's disease cases marked by gait and mobility problems, and rose to 25 percent higher for dementia-associated Parkinson's, although that subgroup showed a weaker association overall with the distance relationship.
While the findings only show an association – and don't prove that dry cleaners or dry-cleaning chemicals like TCE are causing people to develop Parkinson's disease – the findings are a cause for concern.
"Our county-level association map revealed a broadly consistent pattern across much of the US linking residential proximity to dry cleaners with Parkinson's disease risk," the researchers write in their paper.
"These spatial patterns suggest that some regions may be particularly vulnerable to environmental contamination from dry cleaners, potentially reflecting differences in vapor intrusion risk related to aging infrastructure, geology, or population density."
Related: Dry Cleaning Chemical Could Be Major Cause of Parkinson's, Scientists Warn
The researchers acknowledge a number of limitations with their study, including that the way they measured dry cleaners – based on 2013 data for where over 30,000 dry cleaning businesses were located – doesn't accurately capture relevant factors like chemical amounts of TCE or other chemicals, building characteristics, or business activity patterns.
But based on what we already know about the scale of this issue, the researchers say it's further evidence that there's a very serious issue here.
"Our findings suggest that chemicals used in dry cleaning may contaminate nearby neighborhoods and contribute to Parkinson's disease risk," the researchers write.
"Our study provides evidence supporting the need for targeted disease surveillance and further environmental investigation for possible remediation."
The findings are reported in npj Parkinson's Disease.
This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.