Lithium in Water: Sources, Mobility, and Health Implications

Lithium is a naturally occurring element found in drinking water, raising questions about its environmental behavior and potential health effects. While widely known for its use in psychiatric treatments, lithium also enters water systems through natural and human-related sources. Understanding its presence, mobility, and biological interactions is essential for assessing any risks or benefits.

Sources in Aquatic Environments

Lithium enters water systems through geological and human activities. Igneous rocks, particularly granites and pegmatites, contain lithium-bearing minerals such as spodumene and lepidolite, which release lithium into groundwater and surface water through weathering. Regions with lithium-rich deposits often have higher concentrations in water. Volcanic activity also contributes, as hydrothermal fluids transport lithium from deep within the Earth’s crust.

Human activities significantly impact lithium levels in water. Mining operations, especially those extracting lithium for batteries, release wastewater containing lithium into rivers and lakes. Lithium brine extraction, used in South America’s Lithium Triangle, pumps lithium-rich groundwater to the surface, where evaporation concentrates the element, and residual lithium can seep into nearby water systems. Industrial processes such as ceramics, glass production, and aluminum smelting also discharge lithium-containing effluents into municipal water supplies if not adequately treated.

Pharmaceutical and personal care products contribute to lithium contamination. Medications like lithium carbonate and lithium citrate, prescribed for psychiatric conditions, are excreted by patients and enter wastewater. Conventional treatment plants do not effectively remove lithium, allowing trace amounts to persist in discharged effluent. A study in Environmental Science & Technology found wastewater effluent contained lithium concentrations between 1 and 15 µg/L, varying by region and treatment efficiency. Lithium-based greases, used in automotive and industrial applications, also leach into stormwater runoff.

Agricultural practices add to lithium levels in water. Fertilizers derived from lithium-rich minerals introduce small amounts into irrigation water and soil, eventually reaching groundwater. Lithium-containing pesticides, though less common, also contribute. In coastal regions, seawater intrusion into freshwater aquifers raises lithium concentrations, as ocean water naturally contains an average of 170 µg/L. Desalination processes, increasingly used in arid regions, may concentrate lithium in treated water if not carefully managed.

Chemical Forms and Mobility

Lithium exists in water primarily as a dissolved ion, with its behavior influenced by pH, temperature, and other dissolved substances. In freshwater, lithium appears mainly as the free ion (Li⁺), remaining highly mobile due to its small size and strong hydration shell. Unlike heavier alkali metals, lithium does not readily form insoluble compounds, allowing it to persist in solution and move through hydrological networks.

Lithium interacts with clay minerals, organic matter, and ion exchange processes. In sediments and soils, it can adsorb onto negatively charged surfaces of aluminosilicate minerals like smectite and illite, though this binding is weaker than with other cations such as calcium or magnesium. Lithium adsorption increases in clay-rich aquifers with high cation exchange capacity, where it may be temporarily immobilized. However, changes in water chemistry, such as shifts in salinity or pH, can release lithium back into solution, influencing its persistence in groundwater.

In marine environments, lithium behaves conservatively, meaning its concentration is controlled by physical mixing rather than chemical or biological reactions. Seawater holds lithium at an average of 170 µg/L, with Li⁺ as the dominant form due to high ionic strength. Unlike calcium or silicon, which participate in biomineralization, lithium does not significantly interact with biological processes. Hydrothermal vents contribute additional lithium to seawater by leaching it from oceanic crust, enriching localized areas and playing a role in lithium’s long-term geochemical cycle.

Groundwater systems show considerable variation in lithium concentration and mobility, largely dependent on geological composition. In arid and semi-arid regions, lithium accumulates in groundwater due to prolonged water-rock interactions and limited dilution. Some deep aquifers in the southwestern United States and northern Chile have lithium concentrations exceeding 1,000 µg/L, with residence times ranging from decades to millennia. In contrast, shallow, fast-moving groundwater systems tend to have lower lithium levels due to dilution and shorter contact times with minerals.

Concentration Ranges in Drinking Water

Lithium levels in drinking water vary widely, influenced by geology and environmental factors. Most municipal water supplies contain trace amounts, typically between 1 and 100 µg/L, though some groundwater sources exceed 200 µg/L in lithium-rich regions. A U.S. survey found an average of 7 µg/L in public water systems, with higher concentrations in areas with lithium-bearing rock formations. Similar patterns have been observed in Europe, where studies in Denmark and Austria reported drinking water concentrations up to 170 µg/L, depending on local geology.

Water treatment processes do not specifically target lithium removal. Unlike contaminants such as lead or arsenic, which are actively filtered out, lithium remains largely unaffected by conventional treatment methods. Reverse osmosis and ion exchange can reduce lithium levels, but these techniques are not widely used for municipal water treatment. Consequently, populations relying on groundwater may consume higher lithium levels than those using surface water, where dilution lowers concentrations.

Epidemiological studies have examined potential health correlations with lithium exposure in drinking water. Research in Texas found some groundwater sources exceeding 100 µg/L, while studies in Japan and Lithuania reported similar upper-range values in select municipal supplies. In contrast, regions with low-lithium bedrock, such as parts of Scandinavia, consistently report drinking water levels below 10 µg/L. These differences have prompted discussions on whether long-term lithium exposure through drinking water has measurable physiological effects.

Biological Interactions

Lithium is readily absorbed in the gastrointestinal tract and distributed throughout the body via the bloodstream. Though it has no well-defined physiological role, it interacts with cellular processes, particularly in the nervous system. Lithium can substitute for sodium and potassium in certain biochemical pathways, affecting neurotransmitter release, neuronal excitability, and intracellular signaling. While these effects are well-documented in psychiatric treatments, the impact of trace lithium exposure from drinking water remains under study.

Some epidemiological research suggests a correlation between higher lithium levels in drinking water and lower rates of depression and suicide. A 2014 study in The British Journal of Psychiatry examined drinking water lithium levels across 18 Japanese municipalities and found lower suicide rates in areas with concentrations above 30 µg/L. However, confounding factors such as socioeconomic conditions and healthcare access complicate definitive conclusions, and further research is needed.

Lithium also affects endocrine function, particularly thyroid activity. Chronic exposure, even at low levels, has been linked to alterations in thyroid hormone synthesis, potentially leading to subclinical hypothyroidism in some individuals. Lithium’s inhibitory effect on thyroid iodide uptake and hormone release is well-documented in patients undergoing lithium therapy, but its relevance at environmental exposure levels remains unclear. Some studies have noted slight shifts in thyroid hormone levels in populations consuming lithium-rich water, though these changes typically fall within normal ranges.

Regulatory Limits

Despite its presence in drinking water, lithium is not widely regulated as a contaminant. Unlike heavy metals such as lead or arsenic, which have established maximum contaminant levels (MCLs), lithium remains largely unmonitored in most national drinking water standards. The World Health Organization (WHO) acknowledges lithium’s presence but has not set a formal guideline due to insufficient evidence on health risks at environmental exposure levels. Similarly, the U.S. Environmental Protection Agency (EPA) does not enforce a federal limit for lithium in public water supplies, though it has included lithium on its Contaminant Candidate List (CCL) for potential future regulation.

Some countries have taken steps toward monitoring lithium. Health Canada has proposed a screening value of 60 µg/L, based on toxicological data and population exposure estimates. The European Union has also initiated discussions on lithium regulation, with some member states conducting localized assessments. In Germany, recommendations have been made to monitor lithium levels in regions with elevated groundwater concentrations. While no binding limits have been established, these efforts reflect growing awareness of lithium’s presence in drinking water and its potential public health implications.