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Ongoing research by health organizations has linked low concentrations of naturally occurring lithium in drinking water to human health benefits, such as Reduce suicide mortality and other mental health benefits, as well as potential negative side effects For example, autism and Thyroid hormone levelsHowever, there are limited data on the amount and concentration of lithium in drinking water and the levels of lithium that can lead to different health effects.
“In the past, lithium levels in well water have rarely been monitored or measured in the United States, and these new estimates and maps help fill that information gap,” said Melissa Lombard, a research hydrologist with the U.S. Geological Survey and lead author of the study. “Knowing potential lithium concentrations in drinking groundwater across the country allows health researchers to further investigate and better understand how lithium exposure may affect human health.”
Health researchers can combine the results of this USGS-led study with national health data to identify potential links between low-level lithium exposure and health outcomes in people. The research could also help inform well owners, water utilities and water management agencies.
Lithium is not currently regulated in drinking water in the U.S., but the Environmental Protection Agency has added the metal to its most recently released list of unregulated contaminants that public water supplies monitor.
The study, led by the U.S. Geological Survey, estimated lithium concentrations of 30 micrograms per liter or higher in public and private wells in most Western and Southwestern states, including Montana, Wyoming, North Dakota, South Dakota, Colorado, Utah, Nevada, Arizona, New Mexico and Texas. Concentrations of lithium also reached that level in groundwater in Eastern and Northeastern states, but to a lesser extent.
The study focused on the formation of lithium in natural processes because the metal is found in certain minerals and can dissolve in groundwater. Concentrations of lithium naturally occurring in groundwater are much lower than those in medications used to treat bipolar disorder and depression.
The U.S. Geological Survey developed a machine learning model that incorporated data from 18,000 wells to estimate lithium levels in groundwater across a wide area of the U.S. The study classified lithium concentration estimates into four categories: less than 4 micrograms per liter of water, between 4 and 10 micrograms, between 10 and 30 micrograms, and above 30 micrograms. These ranges were chosen based on observed lithium concentrations in water samples used in the model, as well as health-based screening levels.
Studies by the U.S. Geological Survey and the EPA determined that 10 micrograms of lithium per liter of water is a health screening level. HBSLs are established for certain contaminants when EPA regulations are not yet in place. Although HBSLs are not regulated, they may indicate potential human health concerns and help inform future health research efforts.
The four main types of information considered when estimating lithium concentrations are well depth, average annual precipitation, soil chemistry, and the location of the well within the watershed, such as how close the well is to a stream.
Lithium concentrations are likely to be higher when the well is deep, precipitation is low, and the surrounding soil contains lithium. The relationship between lithium concentration and the location of the well within the watershed is not so straightforward. The model developed in this study uses machine learning to identify these complex patterns.
Researchers at the U.S. Geological Survey’s New England Water Science Center collaborated with partners at the Desert Research Institute and public health experts at the University of Toronto on the study.
For more information on well water testing, contact your state health department.
this New article led by the USGS Published in the journal Environmental Science & Technology.
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