Lithium in Tap Water Exceeds Federal Screening Level in Tribal Communities

Lithium is used in the batteries that power electric cars and mobile phones. This same metal is also present in the drinking water supplied to many households across the western United States.

Scientists from the Columbia University Mailman School of Public Health tested tap water from 673 homes in Tribal communities across Arizona, Oklahoma, North Dakota and South Dakota.

For most of these households, lithium concentrations in the water were higher than the level considered safe under a federal screening benchmark.

The research forms part of the Strong Heart Family Study, an ongoing investigation into heart health among American Indian adults, conducted in collaboration with the participating Tribal Nations.

Lithium in tap water

The median concentration in household water samples was 35.6 micrograms of lithium per litre. Lithium enters water naturally as rainfall and groundwater pass through lithium-containing rock.

The U.S. Geological Survey (USGS) has established a non-enforceable drinking-water screening level of 10 micrograms per litre for lithium.

Almost three-quarters of household samples exceeded this threshold.

All Arizona samples were above the screening level. The figure was 93 percent in the Dakotas, compared with 35 percent in Oklahoma.

A baseline for lithium exposure

As the body excretes lithium in urine, urine samples reflect recent exposure. To enable fair comparisons between participants, researchers compared lithium with creatinine, a marker used to account for differences in sample dilution.

Among the 613 participants tested at both visits, levels showed very little change. Median urinary lithium was 30.8 micrograms per gram of creatinine at the first visit and 31.2 at the second.

Lithium levels in household water corresponded with urinary lithium at both visits. Tap water alone accounted for roughly 29 percent of the variation between individuals.

“By linking individually matched household drinking water measurements with biomonitoring data collected over more than a decade, our study establishes an important baseline for understanding environmental lithium exposure in U.S. communities,” said Dr. Ana Navas-Acien, a co-author of the study.

“The findings underscore the value of combining environmental sampling with biomonitoring to characterize long-term exposure patterns and provide evidence supporting the use of urinary lithium as a biomarker of environmental exposure.”

Where the lithium comes from

Lithium is distributed unevenly beneath the ground. Arizona and the Dakotas sit above lithium-rich rock, whereas Oklahoma has no known deposits.

This underlying geology was reflected in the water results. Median lithium levels were 96.7 micrograms per litre in Arizona and 52.5 in the Dakotas, compared with 6.1 in Oklahoma.

Urinary lithium showed the same pattern. However, people in Oklahoma still had more lithium in their urine than their low water concentrations would suggest, indicating that food or other sources contribute to overall exposure.

“Our findings improve lithium exposure estimates among the Strong Heart Family Study communities and highlight the need for continued environmental monitoring and risk evaluation, particularly as lithium extraction and processing accelerate to meet growing energy demands,” said Ellen Bannon, the study’s first author.

Bottled water and its limits

Bottled water use was common in Arizona and Oklahoma but much less frequent in the Dakotas. People who used it had lower urinary lithium levels, at least before geographical location was considered.

“We also uncovered that although bottled water use was associated with lower urinary lithium levels before accounting for geographic differences, study location remained one of the strongest predictors of exposure,” said Bannon.

Bottled water does not necessarily provide protection. Certain brands contain lithium themselves, with some measuring more than 1,500 micrograms per litre.

The challenge of lithium removal

Once lithium is present in water, removing it is difficult. Reverse osmosis can remove it, but standard treatment methods, including chlorination, cannot; nor can the water softeners used in many homes.

Lithium in drinking water is not regulated either. The U.S. Environmental Protection Agency (EPA) placed it on a watch list in 2022 to determine whether a drinking-water limit is required, but no limit has yet been set.

The researchers urge greater monitoring by federal and Tribal authorities. Concern is heightened in some Tribal communities by limited options for the safe disposal of batteries.

Limitations of the study

The study has notable limitations. Water underwent testing only once, between 2022 and 2024, meaning the results cannot show how concentrations may have changed in previous years.

Researchers were also unable to measure water consumed outside the home, such as at work or in relatives’ homes, which probably contributes to total exposure.

Dietary intake was not assessed, although the researchers do not believe it accounts for the differences between locations.

The National Institutes of Health funded the research. The authors declared no competing interests.

Health effects remain unknown

“The health effects of long-term, low-level lithium exposure remain uncertain,” said Dr. Kathrin Schilling, the study’s senior author and an assistant professor of environmental health sciences at Columbia.

“While lithium has been used safely for decades as a medication to treat bipolar disorder at doses far higher than environmental exposure levels, less is known about the potential health implications of chronic exposure through drinking water.”

Medical lithium doses range from 600 to 1,200 milligrams daily, greatly exceeding the amounts supplied by tap water. Over years, doses at this level can place strain on the kidneys and thyroid.

Evidence relating to the trace concentrations found in water is inconsistent. Some research links lithium in drinking water with thyroid problems and pregnancy complications, while other studies, largely broad population comparisons, suggest possible benefits including lower suicide rates.

Environmental lithium has not yet been examined for heart-related effects. The researchers say carefully designed studies involving individuals are needed to establish the true risks.