Lithium in tap water

There is no federal limit for lithium in drinking water. EPA measured it in public water systems from 2023 to 2025 under its UCMR 5 survey and compares the results with a screening level of 10 µg/L (micrograms per liter, the same as parts per billion), which is not an enforceable standard.

Why EPA measured lithium

Lithium is a naturally occurring metal. It can be found at higher levels in groundwater in arid parts of the western US (EPA). It is on EPA's list of contaminants that may need regulating in the future (the fifth Contaminant Candidate List, CCL 5), and UCMR 5 was meant to show how often and at what levels it occurs (same source).

Lithium is also a medicine. Lithium salts have been used for decades as a mood stabilizer, mainly for bipolar disorder (EPA lithium fact sheet).

What the 10 µg/L screening level is

• EPA has no health advisory and no regulatory standard for lithium in drinking water (EPA lithium fact sheet).
• The 10 µg/L figure is a health reference level (HRL) from the CCL 5 process. It starts from adverse effects seen in patients taking lithium as medicine and applies an uncertainty factor of 1,000. It also assumes drinking water supplies 20% of a person's daily lithium (same source).
• EPA says HRLs are not final determinations about the level needed to protect any particular group of people (same source).
• EPA says it cannot yet confidently estimate the risk for exposures between 10 µg/L and the much higher amounts in a therapeutic dose (same source). It also says the science on lithium's health effects is still evolving (EPA).

For scale, EPA's fact sheet gives this example. In a national study of 1,464 public-supply wells, the top quarter of lithium results ran from 21 to 396 µg/L. Drinking 2.5 liters a day of that water adds up to 0.05 to 1.0 milligrams of lithium a day. The low end of a therapeutic dose is 600 milligrams a day of lithium compounds (EPA lithium fact sheet).

What UCMR 5 found

Nationally, 24.1% of large systems (more than 10,000 people) and 28.5% of systems serving 10,000 or fewer reported at least one lithium result above 10 µg/L (EPA UCMR 5 Data Summary). The screening level has one significant digit, so EPA counts a result as above it only when it is over 15 µg/L (same source).

Of the 50 largest US water systems, 49 reported UCMR 5 results. Lithium was found in 17 of them, and 13 had at least one result above the screening level (how we counted). The highest single results were:

UCMR 5 samples were taken where treated water enters the distribution system (EPA), between 2023 and 2025. Levels at your tap today can differ.

Filters

None of the 97 filters and softeners we track is certified to reduce lithium (checked 16 Oct 2026). None of them claims lithium reduction, and none of their IAPMO R&T listings includes it. We have not searched NSF or WQA for lithium, so a certified filter we don't track may exist. You can search the listings yourself at IAPMO R&T, NSF and WQA.

EPA says lithium cannot be removed by heating, boiling or disinfecting water. Studies, mostly at bench and pilot scale, suggest ion exchange removes it, and some newer adsorption media may too (EPA lithium fact sheet). Those findings are about water treatment methods, not certified home filters. The FDA has not set a lithium standard for bottled water either (same source).

What you can do

1. Check your water quality report. Utilities that found lithium in UCMR 5 must report the average and range (EPA). See how to read your water quality report.
2. If your utility is one of the 50 largest, its page on this site shows its UCMR 5 lithium results, like the systems in the table above.
3. If you are on a private well, UCMR 5 did not sample it. Ask a state-certified drinking water laboratory whether it tests for lithium (EPA). See well water testing.