At a glance
| Chemical family | Naturally-occurring radioactive heavy metal (actinide). A dual hazard: chemically toxic (kidney) and radiologically active (alpha-emitter). In water it is usually present as soluble uranyl-carbonate complexes. |
| CAS number | 7440-61-1 (elemental uranium) |
| Classification | The chemical (kidney) toxicity drives the drinking-water limit; the radiological risk is a smaller added factor at typical water concentrations. EPA MCL 30 µg/L; WHO provisional guideline 30 µg/L. Radionuclides/internalized alpha-emitters are IARC Group 1 as a class. |
| Where you encounter it | Naturally-occurring in groundwater — private wells in uranium-bearing geology (the Colorado Plateau, the Great Plains, parts of New England and the Southwest) are the main high-exposure route. Uranium mining and phosphate fertilizers can add to it locally. It commonly co-occurs with radon (a uranium decay product). |
| Sleep micro environment relevance | Indirect — an ingestion exposure via drinking water, on the Atlas as part of the tap-water picture and the private-well testing story the water hub anchors. |
| Activated carbon capture | Not removed by standard carbon. Removal uses reverse osmosis, anion exchange, or coagulation/filtration. Inferred from standard uranium water-treatment engineering; the uranyl-carbonate anion is not adsorbed by ordinary carbon |
Regulatory & certification status
Uranium is regulated as both a chemical and a radionuclide, but its drinking-water limit is set on the chemical (kidney) endpoint. The rows below give the standards and the natural-occurrence context.
| United States | EPA set an enforceable Maximum Contaminant Level of 30 µg/L for uranium in the 2000 Radionuclides Rule (compliance from 2003), based primarily on protecting the kidneys from uranium's chemical toxicity. Uranium is also covered by the rule's radiological framework (gross alpha limit 15 pCi/L). Regulatory — US EPA |
| World Health Organization | WHO sets a provisional guideline value of 30 µg/L, explicitly driven by chemical (kidney) toxicity rather than radiological risk — "provisional" reflecting uncertainties in the low-dose data. Regulatory — WHO |
| International | Health Canada sets a maximum acceptable concentration of 0.02 mg/L (20 µg/L) for uranium, also on the kidney basis — slightly tighter than the US and WHO values. Regulatory — Government of Canada |
| The 72-hour test window | Not applicable. Uranium is a waterborne ingestion exposure measured by a specialized water lab test (chemical and/or radiological), unrelated to the VOC-emission chamber tests used for mattresses and foam. Inferred — from the ingestion-via-water route versus the material/VOC focus of product emissions testing |
What it is
Uranium is a naturally-occurring heavy metal — an actinide — present throughout the earth's crust. It is weakly radioactive, decaying very slowly (its main isotope, U-238, has a half-life measured in billions of years) through a chain of decay products that includes radium and radon. In water, uranium usually dissolves as uranyl ions that form complexes with carbonate, which keeps it mobile in groundwater and is why it shows up in wells drawing from uranium-bearing rock.
The key to reading uranium correctly is its two distinct hazards. The chemical hazard is kidney toxicity: like several heavy metals, uranium damages the kidney's filtering tubules, and this effect appears at lower doses than the cancer risk from its radioactivity. The radiological hazard is that uranium and its decay chain emit alpha particles, which are harmful when the material is ingested and lodges in the body, adding a small long-term cancer risk. At the concentrations found in drinking water, the kidney effect is generally the limiting one — which is why the EPA and WHO both set their 30 µg/L limits on the chemical endpoint.
It's worth stating what uranium in water is not: it is not evidence of contamination from a nuclear facility, and it is not the enriched, weapons-associated material the word conjures. For the overwhelming majority of affected households, it is a natural geological feature of their groundwater — the same reason their water may also carry radon.
Where you encounter it
From uranium-bearing geology
The dominant source. Uranium dissolves into groundwater as it flows through granite, certain sandstones and shales, and the uranium-rich formations of the Colorado Plateau, the Great Plains, and parts of New England, the Carolinas, and the Southwest. Households on private wells in these regions can exceed the 30 µg/L limit purely from geology, with no industrial input.
From radon's shared origin
Because radon is a decay product of uranium, the two often travel together: a well high in uranium is more likely to also carry radon, and a home with elevated indoor radon in a granite region may have uranium in its water too. Testing for one is a reasonable prompt to test for the other.
From local human additions (secondary)
Uranium mining and milling, and phosphate-based fertilizers (which contain trace uranium), can raise groundwater uranium locally. These are secondary to the natural geological source for most affected wells, but relevant near legacy mining areas.
What the research says
The kidney endpoint
The ATSDR Toxicological Profile for Uranium and the WHO background document both identify the kidney as the critical target organ for chronic uranium ingestion, with markers of tubular kidney effects observed in populations with elevated water uranium. Regulatory This chemical nephrotoxicity, appearing below the level of clear radiological risk, is the basis for the 30 µg/L guidelines.
The radiological picture
As an internalized alpha-emitter, uranium carries a long-term cancer risk that regulators account for through the radionuclides framework (the gross-alpha limit), but at typical drinking-water concentrations this radiological contribution is smaller than the chemical kidney effect. Inferred from the regulatory basis — the MCL is set on the kidney endpoint because it is limiting at these levels The distinction matters because it tells you what you're actually managing: a heavy-metal kidney exposure, not a radiation emergency.
What helps
On a well in uranium geology, test for it. Uranium (and gross alpha) can be added to a well-water panel. It's the households in known uranium regions — and anyone who finds elevated radon — who most need the number.
For water over 30 µg/L, use reverse osmosis or anion exchange. Point-of-use RO at the kitchen sink removes uranium for drinking and cooking; whole-house anion exchange handles the negatively-charged uranyl-carbonate complex at higher flow. See water filters compared.
Test for radon too. Given their shared origin, elevated uranium is a reason to check both water and indoor-air radon.
What does NOT help
- Boiling. Uranium is a dissolved metal; boiling concentrates it as water evaporates, like other dissolved contaminants.
- Standard carbon pitcher filters. They don't remove uranium. Use RO or a system rated for uranium.
- Panicking about radiation. The practical hazard at drinking-water levels is chemical kidney toxicity, not acute radiation — the response is testing and filtration, not alarm.
- Assuming city water has it. Public systems monitor and treat for uranium; the concern is overwhelmingly private wells.
Open questions
- The precise low-dose dose-response for uranium kidney effects, and whether current guidelines carry enough margin, is still refined by ongoing epidemiology. Speculation re: exact low-dose threshold; the kidney target is established
- The combined long-term significance of the chemical plus radiological exposure at sub-MCL levels is not fully quantified. Speculation
- The reach of natural uranium in US private wells is still being mapped, and testing uptake in high-uranium regions remains low. Inferred from USGS groundwater survey work and well-testing rates
Where you meet Uranium across your home
The same compound turns up in more than one place you live. Here's where it shows up in Embr — each links to the full breakdown for that part of your home.
Citations
- US Environmental Protection Agency (2000). Radionuclides Final Rule — uranium MCL 30 µg/L (compliance 2003). epa.gov Regulatory
- Agency for Toxic Substances and Disease Registry (2013). Toxicological Profile for Uranium. atsdr.cdc.gov Regulatory
- World Health Organization. Uranium in Drinking-water — provisional guideline 30 µg/L (kidney basis). who.int Regulatory
- US Geological Survey. Uranium and radon in US groundwater — natural occurrence and distribution. usgs.gov Regulatory
Frequently asked questions
Is uranium in well water dangerous?
It can be, at elevated levels — and it's a natural, not industrial, problem. Uranium is a dual hazard: chemically toxic to the kidneys, and radioactive (an alpha-emitter, with a small added cancer risk). At the concentrations found in some private wells, the kidney (chemical) toxicity is usually the driving concern, which is why the EPA limit of 30 µg/L is set on that basis. It occurs naturally in groundwater in certain geologies — notably parts of the western US and the Great Plains — and private wells are not tested by anyone but the owner.
What is the safe level of uranium in drinking water?
The US EPA enforceable Maximum Contaminant Level for uranium is 30 µg/L, and the WHO's provisional guideline is the same 30 µg/L. Both are set primarily on uranium's chemical toxicity to the kidneys rather than its radioactivity, because the kidney effect appears at lower doses than the radiological risk at these concentrations. Below 30 µg/L the risk is considered acceptable; above it, treatment is warranted — especially for long-term drinking and cooking water.
How does uranium get into drinking water?
Almost always naturally. Uranium is present in many rocks and soils, and it dissolves into groundwater as water moves through uranium-bearing geology — granite, certain sandstones, and the aquifers of the Colorado Plateau, the Great Plains, and parts of New England and the Southwest. Human activities like uranium mining and phosphate-fertilizer use can add to it locally, but for most affected households the source is simply the geology their well draws from. Uranium and radon often occur together, since radon is a decay product of uranium.
How do I remove uranium from water?
Uranium is effectively removed by reverse osmosis, anion exchange (uranium in water is usually a negatively-charged uranyl-carbonate complex that anion resin captures well), and coagulation/filtration at the system scale. A standard activated-carbon filter does not remove it. For a private well over 30 µg/L, point-of-use reverse osmosis at the kitchen sink is the common, effective choice for drinking and cooking water; whole-house anion exchange handles higher flow. Test first to confirm the level.
Related compounds
Embr researches the chemistry of where you live — including the natural hazards in well water. See the methodology page for how this Atlas tags claims by evidence strength, the tap-water hub for the other things in your water, and water filters compared for how to remove uranium.
Last reviewed 2026-07-12. If you find a factual error, contact us.