Radionuclides (uranium, radium)

WTR

0.43health-based level (uranium, pCi/L)

California's enforceable uranium limit sits about 47 times higher than its own health-based goal.

Settled science

Stasis Home ResearchEvery claim on this page is graded against peer-reviewed health research and linked to its primary source.Updated 2026-06

Radionuclides in tap water are almost entirely natural. Uranium and radium leach into groundwater from the rock it sits in. Uranium is a chemical kidney toxin, not a classified carcinogen. Radium is a bone-seeking radiological carcinogen. Both are removed well by reverse osmosis at the kitchen tap. A carbon filter does not touch them.

What it is, and where it comes from

Across the US, the source is almost entirely geology, not industry. Uranium is present in nearly all rocks and soils and dissolves into groundwater over long rock-contact timescales. Radium-226 and radium-228 are decay products of the same uranium and thorium in the rock. As water moves through a uranium- or thorium-bearing aquifer it picks these up, while imported surface water generally carries little of them because its rock-contact time is short. So the radiological signal lives in groundwater-reliant systems. Gross alpha and gross beta are screening sums of total alpha- and beta-particle activity, not specific contaminants, measured first because they are cheap and then speciated to find the radium and uranium behind them.

Why it matters

The two radionuclides that matter here harm the body by different routes. Uranium acts chemically, not radiologically. Its target organ is the kidney, and water-soluble uranium compounds reach the kidney at lower doses than insoluble forms. NTP, IARC, and EPA have not classified it as to carcinogenicity. Radium is the radiological-cancer parameter of the group. Once ingested it concentrates in bone, and chronic exposure to high levels raises the incidence of bone, liver, or breast cancer. In the verified Orange County, California district data behind this brief, for example, radium mostly reads low or not detected, but its mechanism is the reason a 5 pCi/L limit exists at all.

Per ATSDR, the health effects of natural and depleted uranium come from its chemical action, not its radiation, with the kidney as the target organ, and uranium has not been classified as to carcinogenicity by NTP, IARC, or EPA.ATSDR, Natural & Depleted Uranium ToxFAQs (CAS 7440-61-1, Feb 2013)
Per EPA, radium forms from the decay of uranium and thorium, and chronic exposure to high levels can raise the incidence of bone, liver, or breast cancer.US EPA, Radionuclide Basics: Radium
The federal Radionuclides Rule sets enforceable limits of 5 pCi/L for combined radium-226/228, 15 pCi/L for gross alpha activity, 4 mrem/year for beta and photon radioactivity, and 30 µg/L for uranium.US EPA, Radionuclides Rule (federal drinking-water MCLs)
Across the US, uranium is the prominent radiological parameter and a groundwater signal, while imported-surface-water systems read low or not detected. In verified Orange County, California district CCR data, for example, uranium averages single digits in pCi/L with some upper ranges climbing toward the 20 pCi/L state limit, while every detection sits far above the 0.43 pCi/L health goal.Stasis Home verified water-district CCR dataset, Orange County, CA (uranium, gross alpha/beta, combined radium)

What we grade it against

Where the health research draws the line, versus the legal limit.
Contaminant	Health-based level	Legal limit	Source (health-based)
Uranium (pCi/L)	0.43California public health goal	20CA MCL, a feasibility line not a health line	CA OEHHA PHG / SWRCB MCL (via district CCRs)
Uranium (mass, federal)	no separate federal health goal in mass units	30 µg/Lfederal Radionuclides Rule MCL	EPA Radionuclides Rule
Combined radium-226/228 (pCi/L)	no federal MCLG above zero is enforced separately here	5federal MCL	EPA Radionuclides Rule
Gross alpha activity (pCi/L)	screening sum, excludes radon and uranium	15federal MCL	EPA Radionuclides Rule
Gross beta activity (pCi/L)	California screening MCL; federal standard is a 4 mrem/year dose limit	50CA screening MCL	CA SWRCB (via district CCRs)

Health-based levels come from peer-reviewed research and government risk scientists working without cost constraints. Legal limits are enforceable compromises. Your report grades to the health column.

What helps

Direct fixes

Reverse osmosis (under-sink, point-of-use)
Removes uranium and radium well at the kitchen tap. This is the default Stasis answer and folds the radiological parameters into the same RO system already recommended for PFAS, chromium-6, and most heavy metals. Where gross alpha derives largely from uranium and radium, the same removal that controls those two controls gross alpha. There is no separate gross-alpha filter.

Bigger retrofits

Ion exchange (point-of-entry / utility scale)
Anion-exchange resin removes uranium, which travels as a negatively charged uranyl-carbonate complex. Cation-exchange resin, the same chemistry as a water softener, removes radium.
Whole-house treatment is utility and point-of-entry territory, not the residential default. Exposure is by ingestion, so the kitchen tap is the right scope.

Free and behavioral

Activated carbon filter
A carbon-block filter is not an answer for radionuclides.
Activated carbon does not remove uranium or radium. A household with a detected radionuclide and only a carbon filter needs RO, the same move as for arsenic and chromium-6.

Uranium and radium were in the aquifer long before anyone drilled a well into it. The gap is what matters: California's enforceable uranium limit is a feasibility line set far above its own health-based goal, and the same reverse-osmosis system you would already install for other contaminants closes it at the tap. Nothing here is cause for alarm. It is one more parameter the right filter already handles.

Common questions

Is uranium in tap water a cancer risk?

No, not on the current science. Uranium in drinking water acts as a chemical kidney toxin, and the kidney is its target organ. NTP, IARC, and EPA have not classified uranium as to carcinogenicity. Radium, a separate radionuclide, is the one with a radiological cancer mechanism.

Where do these radionuclides come from?

Natural geology. Uranium is in nearly all rock and soil, and the longer groundwater sits against that rock, the more of it dissolves in. Radium-226 and radium-228 form as the uranium and thorium in the same rock decay. Imported surface water spends too little time against rock to pick up much of either, so the signal lives in groundwater-reliant systems.

Will a carbon filter remove uranium or radium?

No. Activated carbon does not remove either one, so a carbon-block pitcher or under-sink carbon filter is not an answer here. The effective point-of-use route is reverse osmosis, which removes both well. Ion exchange handles them at whole-house or utility scale.

What are gross alpha and gross beta on my water report?

They are screening sums, not specific contaminants. Gross alpha measures total alpha-particle activity and gross beta measures total beta-particle activity. Utilities measure them first because they are cheap, then speciate to find the radium and uranium behind any elevated reading. Where gross alpha is driven by uranium and radium, removing those two also controls gross alpha.

Should I worry if my water is under the legal limit?

Being under the legal limit means the utility is meeting the law, and that limit is a feasibility line rather than a health-based target. For uranium, California's own health goal of 0.43 pCi/L sits far below its 20 pCi/L enforceable limit, so a reading can be fully legal and still sit far above the health-based goal. Reverse osmosis at the tap closes that gap without changing anything about your water service.