Lithium is an alkali metal element that exists naturally in the environment and is used medically as a mood stabilizer. Trace amounts of this element are found in the world’s groundwater and surface water supplies due to natural geological processes. Whether lithium in drinking water poses a danger depends entirely on the concentration consumed. Assessing potential health implications requires understanding its origins, its dual nature at different doses, and existing safety standards.
Sources and Natural Occurrence
The presence of trace lithium in water primarily results from the natural geological cycle of the Earth. Lithium is found in igneous rocks and mineral deposits, and the slow process of weathering releases it into the surrounding soil and water sources. The concentration of naturally occurring lithium varies significantly across the globe, depending on the local geology and climate. Groundwater in arid regions, particularly in parts of the Western United States, often exhibits higher concentrations due to greater evaporation and lithium-rich geologic formations.
Human activities also contribute to the element’s presence in water. Anthropogenic sources include the discharge of wastewater treatment plant effluents, which contain traces of pharmaceutical lithium. The increased global use of lithium in batteries also raises a potential future concern regarding waste disposal and runoff. However, the vast majority of lithium found in municipal water supplies is a consequence of natural mineral dissolution.
The Dual Nature of Lithium: Therapeutic vs. Toxic
The safety and effect of lithium are defined by its dose, creating a stark difference between trace amounts in water and therapeutic levels in medicine. Lithium has been a highly effective prescription medication for treating bipolar disorder, acting as a mood stabilizer. In this pharmaceutical context, daily intake is carefully measured, typically in the range of hundreds of milligrams.
The therapeutic window for this medication is very narrow; the difference between an effective dose and a potentially toxic dose is small. This narrow margin necessitates regular blood monitoring for patients to ensure levels remain safe and effective.
Naturally occurring lithium in drinking water is present at trace, environmental levels, often thousands of times lower than a medical dose. Epidemiological studies suggest a correlation between higher natural lithium concentrations in a community’s water supply and positive mental health outcomes, such as reduced rates of suicide. These findings suggest that sustained, low-level exposure may offer a beneficial effect on mood. However, these studies show correlation, not causation, and trace amounts are not a substitute for medical treatment.
Symptoms of Overexposure (Lithium Toxicity)
Lithium toxicity, or poisoning, occurs when the element accumulates in the body to dangerously high levels. This condition almost exclusively results from an overdose of pharmaceutical lithium or chronic, slightly elevated intake combined with factors like dehydration or kidney impairment.
In cases of acute toxicity, where a large dose is ingested quickly, gastrointestinal symptoms typically appear first, including nausea, vomiting, and diarrhea. As lithium is absorbed, it can affect the nervous system, leading to mild neurological signs such as dizziness and hand tremors.
Chronic toxicity, resulting from sustained elevated levels, manifests with more pronounced neurological symptoms. These include confusion, slurred speech (dysarthria), uncontrolled muscle movements (ataxia), and increased reflexes (hyperreflexia). Severe cases can escalate to seizures, kidney damage, and an altered level of consciousness, requiring immediate medical intervention. Toxicity from naturally occurring lithium in public drinking water is considered extremely rare.
Regulatory Standards and Safety Measures
Governmental bodies manage the safety of lithium in drinking water primarily through monitoring, as there is currently no federal mandate for a Maximum Contaminant Level (MCL). The Environmental Protection Agency (EPA) has not established a legally enforceable primary drinking water standard for lithium. Instead, the element is listed under the Unregulated Contaminant Monitoring Rule (UCMR 5) to collect data on its national occurrence.
The EPA uses a non-regulatory Health-Based Screening Level (HBSL) of 10 µg/L to help water systems interpret monitoring results and assess potential risk. Most public water sources have lithium concentrations that fall well below any level considered harmful to human health. Consumers concerned about local concentrations can access their annual Consumer Confidence Report (CCR).
Conventional water treatment processes, such as filtration and disinfection, are generally ineffective at removing lithium. Water systems with naturally high lithium levels can explore advanced treatment options, such as reverse osmosis or ion exchange. The current regulatory approach focuses on data collection to determine if a formal safety standard will be necessary.