Radium

The radioactive metal regulated separately from radon, uranium, and arsenic — most well water tests don't include it unless you ask

EPA MCL

Combined radium (Ra-226 + Ra-228): 5 pCi/L. Gross alpha (which includes radium contribution): 15 pCi/L excluding radon and uranium.

Health concern

Bone cancer (osteosarcoma) and head sinus cancer at chronic high exposures; cumulative bone-burden persists for decades

Testing method

Radiochemical analysis (alpha spectrometry or gamma spectroscopy); $80-150; not on standard panels

Radium is the most-overlooked of the radioactive contaminants on this site. Most well-water conversations stop at radon and uranium. But radium is its own regulatory category, its own health concern, and its own test — distinct from both. Ra-226 and Ra-228 are the two regulated radium isotopes (different parents in the uranium and thorium decay chains, similar drinking-water behavior). The EPA's combined-radium MCL is 5 picocuries per liter, set in 1976 and unchanged since. Several US regions have substantial fractions of private wells exceeding it, and most well owners in those regions have never tested for radium because their standard well panel didn't include it.

Radium is what made the City of Waukesha, Wisconsin, undertake a multi-decade infrastructure project to switch from groundwater to Lake Michigan via a Great Lakes Compact diversion — the only municipal Lake Michigan diversion ever granted. The driving cause was radium in the deep Cambrian-Ordovician aquifer.

What it is and why it matters

Radium is an alkaline earth metal in the same chemical family as calcium, strontium, and barium. The two regulated isotopes:

• Ra-226 — from the uranium-238 decay chain. Half-life: 1,600 years. Decays to radon-222, which then decays through several short-lived daughters to stable lead-206.
• Ra-228 — from the thorium-232 decay chain. Half-life: 5.75 years. Different decay pathway from Ra-226.

Both are radioactive; both behave chemically like calcium; both concentrate in bone when ingested. The cumulative bone burden persists for decades — radium's biological half-life in bone is on the order of 20-40 years. Chronic exposure delivers a slowly-accumulating internal radiation dose to bone-forming tissues.

The historic precedent: the "Radium Girls" — watch-dial painters who ingested radium paint by tipping their brushes with their lips in the 1920s. They developed osteosarcoma, head sinus cancers, and other radiation-induced cancers years later. The 1928 case established radium's bone-cancer risk and informed every subsequent radium standard.

Where it shows up in the US

Radium's geographic distribution follows the geology of uranium-bearing source rocks plus the geochemistry of confined aquifer environments where Ra dissolves preferentially. The major US hot zones:

• Eastern Wisconsin — Waukesha, Brown, Outagamie, Winnebago counties — Ra-226 elevated in the deep Mt. Simon and Wonewoc sandstones of the Cambrian-Ordovician. Many community systems treat or blend; private wells often don't.
• Northeastern Illinois — Kane, McHenry, DuPage counties — same aquifer system, similar pattern.
• Eastern Iowa — scattered exceedances in deep Cambrian-Ordovician wells.
• New Jersey Coastal Plain — Burlington, Camden, Gloucester counties — Ra-228 from Cohansey and Kirkwood sands. NJ DEP maintains Radium Areas program; municipal systems treat. See Coastal Plain Atlantic.
• Texas-Louisiana coast — Tertiary sand aquifers in southeastern Texas and southern Louisiana. Some Houston-area private wells have documented Ra-226 exceedances. See Coastal Lowlands.
• South Central Florida — phosphate-bearing units of the Floridan aquifer.
• Carolinas Piedmont — pegmatite belts produce localized Ra hotspots.

Health effects

The radium-bone cancer link is well-established at high cumulative exposures (Radium Girls; uranium miners exposed to radium dust; high-Ra-region populations in studies from the 1950s-1970s). The dose-response at typical drinking-water concentrations is less certain but the EPA's 5 pCi/L combined-radium MCL was set on bone-cancer-risk grounds.

• Osteosarcoma — the cancer most directly attributable to internal radium exposure.
• Head sinus cancers — radium daughters concentrating in mucous membranes of the maxillary sinuses and mastoid air cells.
• Possible leukemia at very high cumulative exposures.

Children are more sensitive per body weight than adults because their actively-growing bones absorb radium more efficiently. Pregnant women's calcium-supplementation needs can also lead to higher per-kg radium uptake. The MCL is set for sensitive populations.

Testing

Radium testing is not on standard well-water panels. The relevant tests:

• Combined radium (Ra-226 + Ra-228) — the regulatory test. Uses radiochemical separation followed by alpha or gamma spectrometry. Costs $80-150 at certified labs.
• Gross alpha — sometimes used as a screening test; if gross alpha is below 5 pCi/L (excluding radon and uranium contribution), radium is unlikely to exceed the MCL. Cheaper than radium-specific tests; about $30-50.
• Sample collection — standard plastic bottle, acid-preserved. The lab needs significant volume (often 1 liter) for the radiochemistry; follow the lab's specific instructions.
• Frequency: at well purchase if you're in a known hot zone; every 5 years thereafter. State health departments in WI, IL, NJ, IA maintain hot-zone maps.

Treatment

Treatment depends on which radium isotopes dominate and on co-existing water chemistry:

• Cation exchange (water softener) — radium behaves chemically like calcium and is partially removed by standard sodium-cycle softeners. Removal efficiency depends on resin selectivity; some softeners labeled "radium reduction" use specialty resins. Brine disposal becomes a regulatory issue at high radium concentrations.
• Reverse osmosis — removes 95%+ of radium. Best at point-of-use.
• Lime softening — used at municipal scale; rare for residential.
• Specialty radium-removal media — manganese dioxide-based, BaSO4-based; more aggressive than softeners for high-concentration situations.

Spent radium-removal media and softener brine become low-level radioactive waste at high concentrations — a regulatory consideration that doesn't apply to most consumer treatments.

Aquifers where this is a concern