Study Links Contaminated Groundwater To Higher Parkinson’s Disease Risk

A large study conducted in the United States suggests that the age and quality of groundwater used for drinking may influence the risk of developing Parkinson’s disease—a finding that could also hold relevance for countries like India, where millions rely on groundwater as their primary source of drinking water.

Parkinson's disease is a progressive, incurable neurodegenerative disorder caused by the loss of dopamine-producing brain cells, primarily affecting motor function in adults over 60. A particularly worrying pattern is the high proportion of younger patients. Nearly 40–45 per cent of cases in India are reported among people aged between 22 and 49 years, indicating a significant trend of early-onset Parkinson’s disease.

The research, which will be presented at the American Academy of Neurology Annual Meeting, indicates that communities consuming relatively newer groundwater may face a higher risk of Parkinson’s disease because such water is more likely to be exposed to modern pollutants. However, the researchers emphasised that the study shows only an association and does not establish a direct cause-and-effect relationship.

Scientists say drinking water can be an important pathway through which people are exposed to environmental pollutants. Groundwater that has formed from rainfall over the past 70 to 75 years is more vulnerable to contamination from agricultural chemicals, industrial waste, and other pollutants present on the surface. In contrast, older groundwater—often stored deep underground for thousands of years—tends to remain better protected from such contaminants.

The study was led by Brittany Krzyzanowski, a researcher affiliated with the Atria Research Institute in New York City. She conducted the work while at the Barrow Neurological Institute in Phoenix and is a member of the American Academy of Neurology.

To explore the potential link between groundwater characteristics and neurological health, the researchers analysed data from 12,370 people diagnosed with Parkinson’s disease and compared them with more than 1.2 million individuals without the condition. Participants were matched by age, sex, race, and ethnicity, and lived within about three miles of 1,279 groundwater sampling sites located across 21 major aquifers in the United States.

The research team examined two key factors: the age of groundwater and the type of aquifer supplying the water. An aquifer is an underground layer of porous rock, sand, or silt that stores and carries water beneath the Earth’s surface.

One important finding was related to carbonate aquifers, which are largely made of limestone and are among the most common aquifer systems in the United States. In these formations, water moves quickly through cracks and channels in the rock. Because of this rapid movement, contaminants from the surface can enter the groundwater more easily.

The study found that people whose drinking water came from municipal systems or private wells connected to carbonate aquifers had a 24 per cent higher risk of developing Parkinson’s disease compared with those using water from other types of aquifers. When compared specifically with individuals relying on glacial aquifers, the risk appeared even higher—about 62 per cent.

Glacial aquifers, formed more than 12,000 years ago as glaciers advanced and retreated, consist mainly of sand and gravel. In these systems, water moves more slowly through small spaces between particles, allowing natural filtration that may reduce the presence of contaminants.

Researchers also observed that older groundwater appeared to have a protective association. For every increase in groundwater age, the risk of Parkinson’s disease declined slightly. Groundwater that had entered the system within the past 75 years was associated with an 11 per cent higher risk of Parkinson’s disease compared with water that had remained underground since the last Ice Age.

Although the study was conducted in the United States, experts note that its findings could have implications for India, where groundwater forms a major part of the drinking water supply in both rural and urban areas. In many regions, concerns have been raised about contamination from pesticides, industrial discharge, and untreated waste entering groundwater sources.

The researchers say that understanding the origin and quality of drinking water could help communities better assess environmental risks and strengthen safeguards against contamination. However, they also acknowledged certain limitations. The study assumed that people living within a three-mile radius of a groundwater sampling site were exposed to similar water conditions, and individual differences in water sources were not directly measured.

Even so, the findings highlight the broader public health message that environmental exposures—including contaminated drinking water—may contribute to the development of neurological disorders over time. Scientists say further research will be needed to better understand how groundwater quality, pollution, and long-term health outcomes are connected.

Cases of Parkinson’s disease are rising steadily in India, with prevalence estimates ranging from 15 to 43 cases per 100,000 people. Experts warn that the country could carry one of the world’s largest Parkinson’s burdens within the next five years.

Although treatment options such as medication and Deep Brain Stimulation (DBS) are available, major challenges remain in terms of public awareness, timely diagnosis, and access to specialised care, say neurologists.