Lithium
Lithium is a natural metal that seeps into groundwater from rock, and about a quarter of US water systems have reported levels above EPA's 10 ppb screening level. It is also a medicine, but tap water carries thousands of times less than a medical dose. Studies point both ways, possible benefits and possible risks in pregnancy, and none of it is proven.
EPA's screening level for lithium, our line
10 ppb
There is no legal limit for lithium. EPA's 10 ppb is a lifetime screening level, and the research behind any number here is mixed.
Lithium: what is it, and where does it come from?
Lithium is a light metal that dissolves into groundwater from rock.
Almost all of it in US tap water is natural, and it runs highest in older groundwater in the dry West and the Great Plains. Surface water, which serves much of coastal California, usually runs lower. Battery making and recycling, lithium mining and brine extraction are a smaller but growing local source.
Lithium is common: in EPA's latest national survey of unregulated contaminants (UCMR 5), about 37 percent of public water systems had at least one result at the 9 ppb reporting level or higher, and 24 percent of large systems and 28.5 percent of small ones had a result above 10 ppb.
The same element, at far higher doses, is a prescription mood stabilizer for bipolar disorder.
Lithium: why does it matter?
Lithium is unusual because the studies point in both directions, and almost all of them compare places rather than measure what each person drank. On the benefit side, pooled studies link areas with more lithium in their water to lower suicide rates, and studies in Denmark and the US link higher levels to less dementia, stroke and cancer.
Other careful studies found nothing: a Danish study of 3.7 million adults and a pre-registered Swiss study found no suicide link, and a Scottish study found no dementia benefit at very low levels.
On the caution side, a large Danish study linked higher lithium in a mother's tap water during pregnancy to a higher autism risk in her child, studies in the Andes where water lithium runs very high linked it to smaller babies and shifts in thyroid hormones, and a 2026 California study linked it to a childhood heart-rhythm condition.
EPA's 10 ppb comes from side effects in patients taking medical doses, divided down by a large safety margin, not from harm seen at tap-water levels. The fair reading: tap-water lithium may matter for health in ways not yet understood, with possible benefits for adults and possible risks in pregnancy, and none of it is proven.
In EPA's fifth national survey of unregulated contaminants (July 2026 data summary), 3,773 of 10,313 public water systems had at least one lithium result at or above the 9 ppb reporting level, and 2,747 had a result above EPA's 10 ppb screening level.
US EPA, The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) Data Summary, July 2026
In a Danish study of 8,842 children with autism and 43,864 controls, higher lithium in the mother's tap water during pregnancy was linked to 46 percent higher odds of autism in the top quarter (above 16.78 ppb) versus the bottom quarter (below 7.39 ppb).
Pooled across 15 studies covering 1,286 localities in seven countries, areas with more lithium in tap water had lower suicide rates.
A pre-registered study of 1,043 Swiss municipalities over 40 years found no link between tap-water lithium and suicide rates.
US counties with more lithium in public water had about 3 to 4 percent lower dementia prevalence and incidence among about 62 million Medicare beneficiaries, in a nonlinear pattern.
Among 2.3 million California children, counties above the 10 ppb screening level had 29 percent higher odds of Wolff-Parkinson-White syndrome, an extra electrical pathway in the heart.
Lithium: what do we grade it against?
The table below lists each level that applies to Lithium, what it is based on and who set it, and says which ones are enforceable.
| Contaminant | Health-based level | Source (health-based) |
|---|---|---|
| Lithium (ppb) | 10 EPA lifetime screening level, our line | US EPA, UCMR 5 lithium fact sheet, 2023 |
| Lithium, if tap water were the only source (ppb) | 60 USGS drinking-water-only benchmark | Lindsey et al., USGS, 2021 |
Health-based levels come from peer-reviewed research and government risk scientists working without cost constraints, while legal limits are enforceable compromises. Your report grades to the health column.
What helps against Lithium?
The approaches below are the ones people use for Lithium at home. Each entry says what it does and what it cannot do, and not every one helps.
Direct fixes
A filter with tested lithium removal
If your level is high and you are pregnant or planning to be, lowering it is reasonable while the research is unsettled.
Boiling does not remove lithium. Ask for a filter whose test data names lithium.
Free and behavioral
Know your number before you act
No study has shown harm at tap-water levels, and some point to possible benefits for adults. A result above 10 ppb is a reason to read the evidence, not to panic.
Common questions about Lithium
Isn't lithium a medicine?
Yes. At much higher doses it is a prescription mood stabilizer for bipolar disorder. Medical doses are typically thousands of times more than what tap water supplies. EPA built its 10 ppb screening level from side effects in patients on those doses, divided down by a large safety margin.
Why do the studies disagree?
Most compare places rather than measure what each person drank, so differences between places, such as geology, other minerals, income or rural living, can show up as a lithium effect. The suicide results split this way: positive in pooled studies of places, and null in a Danish study that followed 3.7 million individual adults and in a pre-registered Swiss study.
I'm pregnant. Should I worry about a high reading?
Nothing is proven, but the caution signals in this research center on pregnancy: a large Danish study linked higher lithium in a mother's water to higher autism risk, and studies where water lithium runs very high linked it to smaller babies and thyroid shifts. If your level is high and you are pregnant or planning to be, it is reasonable to lower it with a filter tested for lithium. Boiling does not remove it.
How common is lithium in US tap water?
Common. In EPA's latest national survey, about 37 percent of public water systems reported lithium at or above the 9 ppb reporting level, and about a quarter had a result above 10 ppb. Western groundwater runs highest; surface-water supplies usually run lower.
Sources cited for Lithium
Every number on this Lithium page traces to one of the 8 sources below: 5 peer-reviewed, 3 government or regulatory.
Peer-reviewed
- Liew Z, et al., Ritz BR. Maternal lithium in drinking water and autism in offspring in Denmark. JAMA Pediatrics, 2023
- Memon A, et al. Naturally occurring lithium in drinking water and suicide rates: meta-analysis of ecological studies. British Journal of Psychiatry, 2020
- Pichler EM, et al. No association between lithium and suicides in a pre-registered Swiss study. Journal of Affective Disorders, 2024
- Hwang SH, et al. Low-dose drinking water lithium and dementia: a nationwide US ecological study. Environmental Pollution, 2026
- Teraoka JT, et al., Marcus GM. Lithium in drinking water and Wolff-Parkinson-White diagnoses. Journal of Clinical Investigation, 2026
Government & regulatory
- US EPA, The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) Data Summary, July 2026
- US EPA, Technical Fact Sheet: Lithium in Drinking Water (EPA 815-F-23-007), 2023
- Lindsey BD, et al. Lithium in groundwater used for drinking-water supply in the United States. Science of the Total Environment, 2021 (USGS)