A US population-based case-control study showed that drinking water from new groundwater sources was associated with a higher risk of developing Parkinson’s disease.
The risk of Parkinson’s was 24% higher when drinking water was obtained from municipal groundwater systems or private wells fed from carbonate aquifers, compared with all other aquifer types (OR 1.24, 95% CI 1.18-1.30), reports Brittany Krzanowski, PhD, of the Atria Research Institute in New York City.
This risk increased by 62% compared with drinking water from glacial aquifers (OR 1.62, 95% CI 1.45-1.81), Krzyzanowski said in research released ahead of the annual meeting of the American Academy of Neurology.
The findings suggested a protective trend depending on the maturity of the water source. For older groundwater within carbonate systems, the risk of Parkinson’s decreased by approximately 6.5% for each standard-deviation increase in groundwater age. People receiving Anthropocene-age groundwater in carbonate systems – water that has entered the ground in recent decades – had a higher risk of Parkinson’s than those using Pleistocene-age water, which is thousands of years older (OR 1.11, 95% CI 1.02-1.20).
“We found that characteristics of the groundwater in a town or city — such as the type of aquifer and the age of the water — were associated with differences in the risk of Parkinson’s disease,” said Krzyzanowski, who conducted the study at the Barrow Neurological Institute in Phoenix.
“This matters because it suggests that groundwater conditions may influence risk, possibly depending on how well the underlying geology protects from surface contaminants,” she told. MedPage Today. “Overall, these findings help to clarify how environmental exposures in drinking water may play a role in the development of Parkinson’s disease.”
Krzyzanowski observed that older groundwater generally contains fewer anthropogenic contaminants such as pesticides because it is generally deeper and better preserved than newer sources. He said carbonate aquifers are made of limestone that dissolves easily, allowing contaminants to move quickly through cracks, while glacial aquifers are made of sand and gravel that filter water more effectively.
The findings support growing evidence that environmental factors may play a role in Parkinson’s risk. In 2025, a study led by Krzyzanowski showed that living within 1 mile of a golf course was more than twice as likely to develop Parkinson’s disease compared to living more than 6 miles away. Other research linked industrial solvents like trichlorethylene in drinking water to a higher risk of Parkinson’s years later.
The current study included 12,370 Medicare beneficiaries with Parkinson’s disease and 1.22 million controls matched by age, sex, and race and ethnicity.
All participants lived within 3 miles of 1,279 groundwater sampling sites in 21 major U.S. aquifers. Groundwater age, aquifer type, and drinking water source were evaluated as a proxy for neurotoxicant exposure, with adjustment for age, sex, race, smoking, income, urban or rural residence, and air pollution.
Although the link between water sources and Parkinson’s is not fully understood, Krzyzanowski suggested that “the most likely explanation is exposure to environmental pollutants in drinking water – such as pesticides or industrial chemicals – which can damage dopamine-producing neurons in the brain, leading to Parkinson’s disease.”
Krzyzanowski said more research is needed to identify which contaminants in drinking water may be most important. In the meantime, protecting aquifers from toxic contamination, improving monitoring of groundwater pollutants, having private wells tested annually and strengthening water treatment systems can help reduce potential risks, he said.
