Lithium

Lithium is a naturally occurring metal, found at higher levels in some groundwater, especially in the arid West. EPA has no legal limit and no health advisory for lithium in drinking water. From 2023 to 2026, EPA had public water systems test for it under its fifth Unregulated Contaminant Monitoring Rule (UCMR 5), to learn how common it is. EPA compares those results with a health reference level of 10 micrograms per litre, a screening value it uses to decide which contaminants need more study, not an enforceable standard. EPA based that figure on effects seen in patients taking lithium as medication, at doses far higher than drinking water supplies, and says it cannot yet confidently estimate the risk between that level and therapeutic doses. Because EPA rounds results to one significant figure, it counts a result as above the reference level from 15 µg/L. In EPA's final data, about one in four tested systems had at least one result at that level. Boiling does not remove lithium. EPA says early research suggests water-treatment methods such as ion exchange can remove it, and it is still reviewing the evidence. Lithium results on this site are for information only and never count toward a city's water-quality verdict.

Sources:

• EPA, The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) Data Summary: July 2026 (EPA 815-S-26-007, July 2026)
• EPA, Technical Fact Sheet: Lithium in Drinking Water, A Resource for Primacy Agencies (EPA 815-F-23-007, October 2023)