Radium in Drinking Water: Risks & How to Remove It

What Is Radium?

Radium is a naturally occurring radioactive element with atomic number 88, formed as a decay product of uranium and thorium in rocks and soil. Two isotopes drive drinking water exposure: Ra-226, which has a half-life of 1,600 years and is produced by the decay of U-238, and Ra-228, which has a half-life of 5.75 years and is produced by the decay of Th-232. Ra-226 is an alpha emitter; Ra-228 is a beta emitter, though its short-lived decay progeny produce alpha radiation as well. A third isotope, Ra-224, appears in some aquifers but decays within days.

Radium in water is colorless, odorless, and tasteless. Detection requires radioactivity measurement, reported in picocuries per liter (pCi) — one picocurie equals 0.037 radioactive disintegrations per second. Standard lab tests for public water systems measure combined Ra-226 and Ra-228 activity, and EPA regulates the sum of the two.

Pierre and Marie Curie discovered radium in 1898, isolating it from pitchblende ore in Paris. For the first four decades of the 20th century, radium was marketed as a health product: radium-laced drinking tonics like Radithor, radioluminescent dial paint, and cosmetics. The radium girls — dial painters at US Radium Corporation plants in New Jersey, Illinois, and Connecticut — ingested radium by licking brush tips to shape the bristles. Roughly a hundred of them died of radium-induced bone cancers and jaw necrosis, and their lawsuits in the late 1920s established the legal basis for workplace radiation standards and helped define the biological behavior of ingested radium in humans.

Today, almost all radium exposure comes from natural sources — primarily groundwater that has contacted uranium- and thorium-bearing rock. It is the most common radionuclide in violation of federal drinking water standards in the United States.

How Radium Gets Into Drinking Water

Natural Dissolution from Aquifer Rocks

The primary pathway is slow dissolution from aquifer rock. Granite, shale, and certain sandstones carry trace uranium and thorium distributed through the mineral matrix. As these parent isotopes decay over geologic timescales, the radium daughters build up in the rock. Groundwater flowing through the formation — especially water with low dissolved oxygen, elevated chloride, or high total dissolved solids — mobilizes radium into solution. Contact times of decades to thousands of years allow radium concentrations to accumulate far above what brief surface water exposure produces. Deep confined aquifers with reducing chemistry and high salinity are the most common radium reservoirs.

Groundwater vs Surface Water

Radium is overwhelmingly a groundwater problem. Surface water rarely exceeds the federal limit because rivers and lakes do not dwell long enough in contact with radium-bearing rock, and suspended sediment adsorbs much of any dissolved radium. EPA’s monitoring data show that combined radium exceedances are concentrated in community systems that pump from sandstone, limestone, and crystalline bedrock aquifers. Systems that draw from reservoirs or rivers almost always report non-detect results.

Industrial Sources

Human activities concentrate radium in specific waste streams. Uranium mining and mill tailings release radium through seepage and windblown dust. Phosphate mining — active in Florida, Idaho, and North Carolina — generates phosphogypsum stacks with elevated radium activity. Coal combustion residuals, including coal ash ponds, contain radium that can leach into groundwater. Oil and gas produced water, especially from shale formations like the Marcellus and Bakken, often contains radium well above drinking water limits; regulated disposal of these fracking brines has become a growing concern, even though public water supplies rarely draw directly from those formations. Historic radium dial factories and tonic bottling plants still appear on state environmental cleanup lists.

Geographic Hotspots

Region	Primary Aquifer	Context
Midwest (IL, IA, WI, MN)	Cambrian-Ordovician sandstone (Mt. Simon, Jordan)	Highest combined radium detections in US — many small community systems exceed MCL
Northern Illinois	Mt. Simon sandstone	Cities like Joliet historically >5 pCi/L
Central/Southern Plains	Ogallala and others	Ra-226 elevated in parts
South-central TX	Hickory Aquifer, Edwards-Trinity	Combined radium elevated in multiple counties
NJ Pine Barrens / Kirkwood-Cohansey	Kirkwood-Cohansey sand	Ra-224 concerns
Southeast coastal plain	Floridan aquifer margins	Mixed detections

If you draw from one of these aquifers — whether through a public utility or a private well — radium is worth testing for alongside arsenic and uranium, which often co-occur.

Health Effects

Radium is an IARC Group 1 carcinogen, classified as carcinogenic to humans based on the radium dial painter cohorts and supporting animal data. EPA classifies radium as a Group A known human carcinogen. The biological mechanism is direct: ingested radium behaves like calcium, gets absorbed from the gut, and deposits in mineralizing bone tissue. Once embedded in bone, the alpha and beta particles emitted by Ra-226, Ra-228, and their decay products irradiate adjacent cells — bone marrow, endosteal surfaces, and osteoblasts — causing DNA damage that accumulates over years.

Bone Cancer and Osteosarcoma

The clearest human evidence comes from the radium girls cohort, roughly 1,000 dial-painting workers tracked from the 1920s onward. About 100 died of radium-induced bone sarcomas and head/sinus carcinomas, often decades after their initial exposure. Those workers carried body burdens orders of magnitude higher than anything possible from drinking water, but the dose-response curve they anchored has been used to project risk at lower levels. Modern epidemiology at typical drinking water concentrations shows small but measurable excess bone cancer risk, particularly for osteosarcoma.

Other Cancers

Radium-induced head carcinomas — tumors of the paranasal sinuses and mastoid air cells — were a defining injury in the dial painter cohort, driven by radon gas released as Ra-226 decays inside bone. Ra-228 beta radiation reaches bone marrow and has been linked to leukemia in animal studies and in occupationally exposed workers. Because radium follows calcium, some research has examined breast cancer risk as well, though the epidemiological signal at drinking water doses is weak.

Birth Defects and Developmental Risk

Radium crosses the placenta and deposits in the fetal skeleton during mineralization. Prenatal exposure is a concern in high-radium regions, though human data are limited because cohort sizes are small. Animal studies show measurable incorporation of radium into fetal bone from maternal exposure.

Dose-response

EPA’s quantitative risk assessment estimates roughly 44 excess cancers per million people consuming water at the 5 pCi/L MCL over a 70-year lifetime. This is the figure that justifies an Maximum Contaminant Level (MCL) at the limits of detection rather than at a “safe” threshold — for a genotoxic alpha emitter, the agency assumes no threshold exists.

Children

Children absorb a larger fraction of ingested radium than adults and incorporate it more efficiently into growing bone. Per unit of body weight they drink more water, and a longer remaining lifespan means more time for a latent cancer to develop. Families in high-radium regions with young children have the strongest case for home treatment even when their utility reports compliance with the 5 pCi/L standard.

EPA Regulation and Limits

EPA regulates combined radium (Ra-226 + Ra-228) at a Maximum Contaminant Level of 5 pCi/L. The standard was set in 1976 under the Safe Drinking Water Act as part of the first interim radionuclide rule, and it was reaffirmed without change in the 2000 Radionuclides Rule. The Maximum Contaminant Level Goal (MCLG) is zero, reflecting EPA policy that no level of a known human carcinogen is demonstrably safe.

The radionuclides framework covers several related standards. Gross alpha particle activity (excluding radon and uranium) is capped separately at 15 pCi/L — a screening metric that can trigger isotope-specific testing. Beta particle and photon activity is limited to a dose equivalent of 4 mrem per year. The 2000 rule added a new 30 µg/L MCL for uranium, but it left the radium standard untouched at the 1976 level of 5 pCi/L despite updated risk models that some public health advocates argue support a lower limit.

Standard	Value	Notes
EPA MCL (combined Ra-226 + Ra-228)	5 pCi/L	Enforceable since 1976
EPA MCLG	0 pCi/L	No safe level for carcinogens
Gross alpha (separate MCL)	15 pCi/L	Excluding radon and uranium
WHO guideline (Ra-226)	1 Bq/L (~27 pCi/L)	Less stringent
NRC occupational limit	Much higher	Not applicable to drinking water

Monitoring frequency depends on system history: utilities with past exceedances test quarterly, while systems with clean baseline samples may drop to reduced monitoring on a multi-year cycle. Small community systems across the upper Midwest have struggled with compliance since the 2000 rule reaffirmation, because treatment to remove radium at the point of entry — typically lime softening or ion exchange — requires significant capital investment that small ratepayer bases cannot easily absorb.

How Widespread Is Radium?

A 2017 USGS analysis of US principal aquifers estimated that radium is detected above the MCL in water drawn from a substantial share of domestic and public wells in the central and eastern states, with roughly 3,400 public water systems serving around 170 million Americans showing at least some detectable radium over the monitoring record. Exceedances are concentrated in sandstone aquifer states: Wisconsin has historically had on the order of 80 community systems exceeding the MCL at various points, and northern Illinois communities have spent tens of millions on blending, radium-selective resins, and new deeper or shallower wells to achieve compliance.

Private wells are not covered by EPA monitoring requirements. USGS sampling suggests that in high-radium regions — parts of Wisconsin, Iowa, Illinois, southeastern Minnesota, and the Texas Hill Country — roughly 10 to 15 percent of private wells exceed 5 pCi/L combined radium, though this varies widely by specific aquifer and depth. A homeowner on a private well in a sandstone belt has no backstop other than voluntary testing.

Produced water from fracking operations in Pennsylvania, Texas, North Dakota, and elsewhere frequently carries Ra-226 and Ra-228 activity well above drinking water limits. Public water systems in those regions are almost never sourced from the same formations, so the direct drinking water risk from fracking brines is limited, but disposal practices — injection, spreading on roads for dust control, or discharge to surface water — have raised concerns about secondary contamination pathways.

How WaterVerge Tracks Radium

WaterVerge pulls combined radium monitoring data from EPA SDWIS (the Safe Drinking Water Information System) for every US community water system. Radium is a regulated radionuclide, so utilities must sample on a schedule tied to their compliance history — quarterly for systems with past exceedances, less often for systems with a clean record. The most recent reported combined radium result appears on each city page, alongside the EPA MCL of 5 pCi/L for direct comparison and a flag for any system with historical exceedances or active violations.

Radium violations — both MCL exceedances and monitoring and reporting failures — are surfaced on the violations panel. Because radium is a slow-moving, naturally driven contaminant, a single quarterly sample above 5 pCi/L is less urgent than a persistent multi-year pattern, and the page distinguishes between the two.

SDWIS only covers public systems. Households on private wells are not represented. If you draw from a private well in a sandstone belt or any of the regional hotspots, the right move is direct testing — see the well water testing guide for sampling protocol and lab selection.

How to Remove Radium

Start with what does not work. Standard activated carbon filters — pitchers, refrigerator filters, basic countertop units — do not remove radium in any meaningful quantity. Boiling concentrates radium rather than removing it, because radium stays with the water as it evaporates only marginally and is left behind in any residue. UV disinfection has no effect on radioactivity. If your water contains radium, a plain carbon block or a rolling boil will not protect you.

Method	Removal Rate	Certification	Best For
Reverse osmosis	90-99%	NSF/ANSI 58	Under-sink drinking water
Ion exchange (cation, softener)	80-97%	NSF/ANSI 44	Whole-house if hardness is also a concern
Lime softening	80-95%	Treatment plant scale	Municipal systems
Distillation	99%+	N/A	Countertop, low flow
Standard activated carbon	Negligible	N/A	Not effective for radium

Reverse osmosis is the strongest point-of-use option for households. An under-sink system with an NSF/ANSI 58 certification specific to radium (or to the broader radionuclides category) will remove 90 to 99 percent of combined radium from drinking and cooking water. RO is efficient because radium ions are large and charged, and the semipermeable membrane rejects them effectively. The tradeoff is water usage and the need to maintain the membrane and pre-filters — see the best reverse osmosis systems guide for selection criteria.

Ion exchange is the primary whole-house option and the most common municipal-scale treatment for radium. Cation exchange resins swap radium ions for sodium or potassium, and water softeners — which use the same chemistry to remove calcium and magnesium — inadvertently remove radium alongside hardness. For households already planning to soften hard water, a properly sized softener doubles as radium treatment. The complication is the brine: regenerating the resin concentrates radium into the backwash stream, and in high-radium regions, utility-scale systems using ion exchange must manage the spent brine as low-level radioactive waste. For a household softener in a moderately affected area, the brine goes to the septic system or sewer at concentrations that regulators generally consider acceptable, but the numbers are worth checking locally. The softeners vs filters guide walks through the decision between a softener and a dedicated contaminant filter.

Distillation removes essentially all radium but produces water slowly and uses considerable energy — a reasonable countertop option for drinking water in small households, impractical at whole-house volumes.

At the utility scale, lime softening has been the traditional treatment, bumping pH high enough to co-precipitate radium with calcium carbonate, and specialty radium-selective resins (such as BaSO4-based media or hybrid resins) are deployed where ion exchange is not feasible. These are not home options.

Check Your City

If you live in the Midwest sandstone belt, northern Illinois, south-central Texas, or any of the aquifer regions listed above, radium monitoring data for your utility is probably on your city page. The most recent combined Ra-226 + Ra-228 result is shown next to the 5 pCi/L MCL, with any violations flagged. Search your city to pull it up.

On a private well in a high-radium region, a combined radium lab test runs roughly $30 to $60 through a state-certified laboratory — cheaper than nitrate and arsenic panels combined, and worth pairing with them. The how to test your tap water guide covers sampling and lab selection. If you also see elevated nitrate, that signals a shallow well drawing from a different part of the aquifer than the deep sandstone radium, and both need separate treatment decisions.