Drinking from newer groundwater may increase your risk of Parkinson’s disease, according to a new preliminary study.

Researchers analyzed Medicare data from more than a million older Americans and found that people living near limestone-based carbonate aquifers faced higher rates of Parkinson’s disease than those near other types of groundwater.

“Newer groundwater, created by precipitation that has fallen within the past 70 to 75 years, has been exposed to more pollutants. Older groundwater typically contains fewer contaminants because it is generally deeper and better shielded from surface contaminants,” study author Brittany Krzyzanowski said in the study’s press release.

Parkinson’s disease affects about 1 million Americans. Its causes are complex, involving genetics, aging, and environmental exposures, including pesticides and industrial chemicals that may seep into soil and groundwater aquifers over time.

The risk was greatest for those drinking relatively “young” water—groundwater within the carbonate systems that had entered the ground within the past several decades.

“Our study found that groundwater age and location is a potential environmental risk factor of Parkinson’s disease,” Krzyzanowski said.

The findings will be presented at the American Academy of Neurology’s 78th Annual Meeting, to be held in Chicago, April 18 through 22.

The Risk in Certain Aquifers

The researchers compared 12,370 people with Parkinson’s to more than 1.2 million without the disease. All lived within three miles of 1,279 groundwater sampling sites across 21 major U.S. aquifers.

People whose drinking water comes from carbonate aquifers had a 24 percent higher risk of Parkinson’s disease than those using other aquifers. When compared against glacial aquifers, the risk increased to 62 percent.

Researchers said the differences in risk may be due to how fast water moves in the aquifers.

Aquifers are underground layers of rock, sand, or gravel that store and carry water.

Carbonate aquifers, the most prevalent aquifers and common in parts of the Midwest, South, and Florida, are made of fractured limestone that allows water—and contaminants—to move quickly.

Glacial aquifers, mostly in the Upper Midwest and Northeast, are composed of sand and gravel left by retreating glaciers. Water moves more slowly through them, which provides more natural filtration.

The study did not identify contaminants in the water.

The Importance of Water Age

Groundwater age also appeared to matter, but only in carbonate aquifers.

Younger water, which entered the ground within the past several decades, was associated with an 11 percent higher risk of Parkinson’s in carbonate systems compared with very old water, some of which dates back over 12,000 years. In these systems, each step up in groundwater age corresponded to a roughly 6.5 percent decline in risk.

“This study confirms prior observations that contaminated water supplies are associated with Parkinson’s disease,” Dr. Caroline Tanner, a neurologist and epidemiologist at the University of California, San Francisco, who studies environmental exposures linked to Parkinson’s and was not involved in the new study, told The Epoch Times via email.

Because chemical use in agriculture has increased, she added, it is plausible that contaminants seeping into certain types of newer aquifers could influence risk.

“There weren’t a lot of toxicants that existed until really the turn of the 20th century,” Dr. Samuel M. Goldman, a neurologist and Parkinson’s researcher at UCSF and the San Francisco VA Health Care System, who studies environmental exposures linked to Parkinson’s and was not involved in the research, told The Epoch Times.

Newer groundwater reflects rainfall from the past several decades—a period of widespread use of pesticides, fertilizers, and industrial chemicals. In carbonate aquifers, water moves quickly through cracks and channels, allowing contaminants at the surface to travel more easily into drinking supplies with less natural filtration.

This timeline also aligns with growing evidence that specific chemicals introduced over the last century increase Parkinson’s risk. One example is trichloroethylene, or TCE, a solvent used in industry for cleaning and degreasing. TCE can linger in soil and groundwater, and research suggests it may raise the risk of Parkinson’s.

In one study, Marines stationed at Camp Lejeune, North Carolina, where drinking water was contaminated with TCE in the 1970s and 1980s, had roughly 70 percent higher rates of Parkinson’s than service members at bases with clean water—a striking example of how long-term exposure to TCE matters. In animal studies, it has been shown to damage the brain cells that produce dopamine.

Older groundwater, by contrast, is often deeper and more isolated from recent surface pollution. In glacial aquifers, slower movement through sand and gravel provides more natural filtering, which may reduce differences between younger and older water.

What Can People Do

Experts say the findings are a reason for awareness, not alarm.

“People should know what’s in their water,” Goldman said. “If it’s a well, have it regularly tested. If it’s a municipal system, they’re required to publish a long list of chemicals.”

Most municipal water is treated to meet EPA standards, which remove or reduce many contaminants. However, no system can guarantee water is 100 percent free of all substances—some trace chemicals may still be present. Checking your local water quality report each year is an easy way to stay informed, he said.

Chemicals to keep an eye on include TCE, certain pesticides such as paraquat and rotenone, nitrates from fertilizers, and lead. Public water systems test for these and publish the results in yearly consumer confidence reports on your local water supplier’s website. Private wells are not regulated, so if that’s your source, Goldman added, testing is the only way to know what’s really in your water.

Filters can also help remove some contaminants. “It’s relatively easy and inexpensive to add an under-sink charcoal filter,” Goldman said. “It’s really good at removing a lot of these toxicants.”

However, drinking water is just one part of reducing exposure. Tanner encourages people to look around their homes, too. “Check what’s in your garage or under your sink,” she said. “Using gloves or masks when handling chemicals can lower your risk.”

Tanner’s previous research with Goldman supports protective measures. Agricultural workers who consistently wore protective gloves and practiced good hygiene had lower associations between pesticide exposure and Parkinson’s than those who didn’t. Their studies also suggest diet plays a role: People who ate more omega-3 polyunsaturated fats appeared to have lower risk, even if they were exposed to certain pesticides.

Water is one of many potential pathways for toxic chemicals linked to Parkinson’s, Tanner said. “These precautions are general, but they are practical steps people can take.”