The type of water a person drinks may lead them to have higher risk of developing Parkinson's disease, a new study has suggested.
People whose drinking water comes from newer groundwater had a higher risk of developing Parkinson's disease than those whose drinking water comes from older groundwater.
Drinking water drawn from carbonate aquifers was associated with a 24 percent higher risk of Parkinson's disease when compared to other aquifer types--and this rose to 62 percent when compared to drinking waters from glacial aquifers.
Aquifers are underground layers of porous rock, silt or sand that hold and transport groundwater.
Newer groundwater—from the past 75 years, in carbonate systems—was found to be associated with an 11 percent higher risk of Parkinson's compared to groundwater from the ice age, i.e. that older than 12,000 years.
Older groundwater generally contains fewer contaminants as it is usually taken from greater depths and are thus better shielded from potential pollution. Carbonate aquifers are the most common in the United States, often containing groundwater more vulnerable to surface contamination.
Glacial aquifers, formed when glaciers advanced and retreated during the ice age, are composed of sand and gravel—and so tend to promote natural filtration.
However, the new study does not prove that newer groundwater causes Parkinson's—-it shows only that there is an association between it and the disease.
The study—due to be presented at the American Academy of Neurology's 78th Annual Meeting, to be held in Chicago between April 18–22—looked at the age of groundwater and the sources from which such is drawn.
"One way to examine our exposure to modern pollution is through our drinking water," study author Brittany Krzyzanowski—of the Atria Research Institute in New York City, who conducted the research while at the Barrow Neurological Institute in Phoenix, Arizona—said in a statement.
"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. Our study found that groundwater age and location is a potential environmental risk factor of Parkinson’s disease."
The study looked at 12,370 people with Parkinson's disease, and more than 1.2 million people without the disease, all of whom lived with three miles of specific groundwater sampling sites across 21 major US aquifers.
Matching for factors including age and sex, the researchers looked at the groundwater age, aquifer type and drinking water source as potential indictors of exposure to neurotoxic contaminants.
It found that of the people with Parkinson's, 3,463 got their drinking water from carbonate aquifers, 515 from glacial aquifers, and 8,329 from other aquifers. Of those without the disease, 300,264 got their drinking water from carbonate aquifers, 62,917 from glacial aquifers and 860,993 from other aquifers.
"We speculate that the apparent protective effect of older groundwater is seen mainly in carbonate aquifers because these systems can show a clearer contrast between newer and older water," Krzyzanowski said in a press release.
"In these aquifers, newly recharged groundwater is more vulnerable to surface contamination, while older groundwater can remain cleaner if it is separated from recent inputs by a confining layer."
Krzyzanowski added: "In contrast, glacial aquifers tend to slow groundwater movement and naturally filter contaminants as water travels underground. As a result, differences in contamination between newer and older groundwater in these aquifers may be smaller and therefore harder to detect."
He said the 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," and while further research is needed, it "may help communities better assess and reduce environmental risks."
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