What is radium and why is it in drinking water?

Radium is a naturally occurring radioactive element that forms as uranium and thorium in rock decay over millions of years. It dissolves into groundwater as water passes through rock formations containing these elements. Deep, confined aquifer systems in the Midwest and Gulf Coast have the highest natural radium levels. Radium behaves like calcium in the body — it deposits in bone and irradiates bone marrow from within, which is what makes long-term exposure a bone cancer risk.

How do I know if my water has radium?

Radium is colorless, odorless, and tasteless. The only way to know your water's radium level is laboratory testing — standard water tests do not include radium. Check your utility's Consumer Confidence Report for 'combined radium' or 'gross alpha' results. Well owners in Illinois, Iowa, Wisconsin, Texas, and Pennsylvania's Reading Prong region should specifically request radium testing from a certified radiological lab.

Does a water softener remove radium?

Yes — cation exchange (water softeners) can remove radium effectively because radium behaves chemically like calcium and barium, which ion exchange resins capture well. This makes water softeners an unusually versatile treatment for radium. Reverse osmosis also removes radium (90%+). Activated carbon does not remove radium.

Is radium in water the same as the Radium Girls story?

The connection is the same element. The Radium Girls were factory workers in the 1920s who painted watch dials with radium-based luminescent paint and were instructed to point their brushes with their lips. They ingested large amounts of radium, which deposited in their bones and caused radiation-induced bone cancer, jaw necrosis, and leukemia. Their deaths and lawsuits established legally that corporations are liable for occupational health hazards and confirmed radium's bone cancer connection — directly informing how radium in drinking water is regulated today.

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Radium in Drinking Water

Radium is a naturally occurring radioactive element found in rock formations across the central and eastern United States. It enters drinking water by dissolving from uranium- and thorium-bearing rock. Radium is a bone-seeking element — it accumulates in bone tissue, delivering ongoing radiation dose from within. The EPA MCL covers combined radium-226 and radium-228 at 5 picocuries per liter (pCi/L). Radium is primarily a concern for public water systems in the Midwest, Gulf Coast, and parts of New England drawing from deep confined aquifers.

Quick Answer

Radium (Ra) has multiple isotopes, of which Ra-226 (alpha emitter, half-life 1,600 years, from uranium decay) and Ra-228 (beta emitter, half-life 5.75 years, from thorium decay) are the primary drinking water concerns. Radium dissolves into groundwater from naturally occurring uranium and thorium in deep sedimentary and metamorphic rock formations. It is highly concentrated in the Cambrian-Ordovician aquifer system underlying Illinois, Iowa, Wisconsin, and Minnesota, and in the Gulf Coast aquifer system in Texas and Louisiana. Radium accumulates in bone tissue in the same manner as calcium — a property that makes it an exceptionally dangerous internal emitter once ingested.

Why Is Radium in Drinking Water a Concern?

Radium in drinking water is not rare: the EPA has identified radium violations in public water systems serving millions of people, primarily in the Midwest and along the Gulf Coast. Illinois, Iowa, Wisconsin, and Texas have had numerous utilities exceed the combined Ra 5 pCi/L MCL. Unlike many contaminants that pose cancer risk primarily through external exposure, radium is dangerous because it substitutes for calcium in bone and teeth, where it irradiates bone marrow from the inside for decades. The Radium Girls — factory workers who ingested radium paint in the 1920s — suffered bone cancer, jaw necrosis, and leukemia, establishing radium's bone cancer connection definitively.

People served by public water utilities drawing from the Cambrian-Ordovician aquifer system in Illinois, Iowa, Wisconsin, Minnesota, and Missouri face the highest radium exposure from public water. Gulf Coast residents in Texas and Louisiana drawing from deep confined aquifers also face elevated radium. Private well owners in these areas — particularly those with deep, artesian wells — should test for radium. Pennsylvania well owners in granite-heavy geology (Reading Prong, Piedmont) are also at elevated risk.

Health Effects of Radium in Drinking Water

Bone cancer — the most well-established risk; radium mimics calcium and deposits in bone, where it irradiates bone marrow from within for decades

Leukemia — from chronic bone marrow irradiation

Jaw necrosis (radium jaw) — at very high doses; historically documented in Radium Girls factory workers

Kidney damage with chronic high-level exposure

Increased risk of all cancers from cumulative internal radiation dose

No acute symptoms at concentrations found in drinking water — all effects are from long-term internal radiation exposure

How Does Radium Get Into Drinking Water?

Natural dissolution from uranium- and thorium-bearing rock into groundwater — the dominant source

Deep confined aquifer systems with long water residence times and reducing conditions

Cambrian-Ordovician aquifer underlying the upper Midwest — Illinois, Iowa, Wisconsin, Minnesota

Gulf Coast aquifer system — Texas, Louisiana

Oil and gas production — produced water and brine from drilling operations can carry naturally occurring radioactive material (NORM) including radium

Legacy radium contamination from industrial use (luminescent paint, medical applications) — localized to specific historical sites

Regulatory Limit

EPA Maximum Contaminant Level (MCL)

5 pCi/L (combined Ra-226 + Ra-228)

The EPA MCL for combined radium-226 and radium-228 is 5 picocuries per liter (pCi/L). Separate MCLs: Ra-226 alone is 5 pCi/L; Ra-228 alone is also 5 pCi/L. The MCLG for both is zero — no level of radioactivity is without risk. The EPA also sets a gross alpha particle activity MCL of 15 pCi/L covering multiple naturally occurring radioactive materials. Radium violations are among the most common radiological MCL exceedances in the U.S., with utilities in Illinois, Iowa, and Texas historically exceeding the limit.

How to Test for Radium in Your Water

Radium testing requires a certified radiological laboratory — it is not included in standard water quality panels. Radium analysis costs $25–$75. Public utilities in affected areas are required to test and report radium levels in Consumer Confidence Reports. Well owners in the Midwest, Gulf Coast, and Pennsylvania's Reading Prong geological formation should include radium in comprehensive testing. The EPA's ECHO database contains radium monitoring data for public water systems.

How to Remove Radium from Drinking Water

Best filter for Radium: Reverse Osmosis Filtration — also effective: Water Softener

These treatment methods have demonstrated effectiveness for Radium removal.

Reverse Osmosis

Reverse osmosis (RO) is the most comprehensive point-of-use water treatment technology available for residential use. It removes 90–99% of dissolved contaminants including PFAS, lead, arsenic, nitrates, and disinfection byproducts by forcing water through a semi-permeable membrane with pores of approximately 0.0001 microns.

PFAS / PFOA / PFOS — 90–99% removalLead — 95–99% removal

Water Softener

A salt-based water softener is the standard whole-home solution for hard water. It uses ion exchange to replace dissolved calcium and magnesium — the minerals responsible for scale, soap scum, and appliance damage — with sodium ions. Softeners protect plumbing and appliances but do not address health-based contaminants.

Scale buildup in pipes, water heaters, and appliancesSoap and shampoo lathering — softened water requires significantly less soap

Frequently Asked Questions

Reverse Osmosis Filtration

Removes: Radium

Water Softener (Ion Exchange)

Removes: Radium

Radon in Well Water

Radioactive Contaminants

Uranium in Drinking Water

Radioactive Contaminants

Data Sources & Provenance

All data on this page is sourced from official U.S. government or public datasets.

EPA Drinking Water Contaminant InformationView source

ATSDR ToxFAQs / Toxicological ProfilesView source

EPA SDWIS — violation and detection dataView source

Last updated: 2026-04-30

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