A new study has found people whose drinking water comes from newer groundwater have a higher risk of Parkinson’s disease than those whose water comes from older groundwater. While the study only shows association and additional research it needed, researchers say this kind of data can help communities better manage and reduce environmental risks that cause health issues.
The study, which will be presented at the American Academy of Neurology’s 78th Annual Meeting in April, looked at groundwater age, aquifer type and drinking water source as potential indicators of exposure to neurotoxic contaminants.
For example, newer groundwater—created by precipitation that has fallen within the past 70 to 75 years—has been exposed to more pollutants. Whereas older groundwater typically contains fewer contaminants because it is generally deeper and better shielded from surface contaminants.
Carbonate aquifers are the most prevalent in the United States, consisting mostly of limestone with water stored in fractures and channels. They often contain groundwater that is more vulnerable to surface contamination due to rapid flow through fractures. Glacial aquifers, formed when glaciers advanced and retreated more than 12,000 years ago, are composed of sand and gravel with water stored in the gaps. These aquifers tend to promote more diffuse flow and natural filtration. In the U.S., carbonate aquifers are common in parts of the Midwest, South and Florida, while glacial aquifers are found mostly in the Upper Midwest and Northeast.
The study, led by Brittany Krzyzanowski while she was at the Barrow Neurological Institute in Phoenix, included 12,370 people with Parkinson’s disease and more than 1.2 million people without the disease who were matched for factors like age, sex, race and ethnicity. All participants lived within three miles of 1,279 groundwater sampling sites across 21 major U.S. aquifers.
According to the study data, people whose drinking water came from municipal groundwater systems or private wells that draw from carbonate aquifers had a 24% higher risk of developing Parkinson’s disease than those whose water came from all other aquifers. They also had a 62% higher risk when compared with people whose water came from glacial aquifers.
The protective effect of older groundwater was found only when water was sourced from carbonate aquifers. For each one-standard-deviation increase in groundwater age, the risk of Parkinson's disease declined by approximately 6.5%.
Krzyzanowski and team also found that newer groundwater—from the past 75 years—in carbonate systems was associated with an 11% higher risk of Parkinson’s disease compared with groundwater older than 12,000 years from the ice age.
“One way to examine our exposure to modern pollution is through our drinking water,” said Krzyzanowski, who is now at Atria Research Institute in New York City. “This study highlights that where our water comes from, including the age of groundwater and the type of water source, could shape long‑term neurological health. While additional research is needed, bringing together knowledge about groundwater and brain health may help communities better assess and reduce environmental risks.”