Radium (Ra-226 + Ra-228)
Ra·Affects bones
A naturally occurring radioactive element that behaves like calcium in the body, depositing in bone where it can irradiate marrow for decades.
Ra
EPA limit
5 pCi/L (combined Ra-226 + Ra-228, MCL)
Most at risk
Well-water households, residents of the Midwest sandstone aquifer belt, the Carolinas Piedmont, and parts of the Mountain West
Found in
Well water
AquaOx filters
YesWater softener (cation exchange) or RO
What it does to you
Health effects
Radium is a bone-seeking element. Once it enters the bloodstream, the body mistakes it for calcium and deposits it into the skeletal matrix, where the two main isotopes (Ra-226 and Ra-228) continue to emit alpha and beta radiation. Ra-226 has a half-life of about 1,600 years, so a single intake stays radiologically active inside the body for the rest of your life.
The principal documented health outcome is bone sarcoma, a rare cancer of the skeletal tissue. Early evidence came from the "Radium Girls" of the 1920s, watch-dial painters who ingested radium from their brushes and developed bone tumors decades later. Modern epidemiological work confirms elevated bone cancer and leukemia rates among populations chronically exposed via drinking water.
The EPA Maximum Contaminant Level is 5 pCi/L for the combined activity of Ra-226 and Ra-228. Many private wells in the Midwest sandstone aquifer belt test above this threshold.
Where it comes from
How it gets into your water
Radium is a natural decay product of uranium and thorium, both of which occur in trace amounts throughout the Earth's crust. Groundwater moving through uranium-rich or thorium-rich formations dissolves radium and carries it into the aquifer.
The most heavily affected US region is the Cambrian-Ordovician sandstone aquifer that underlies parts of Iowa, Illinois, Wisconsin, and Minnesota, where Ra-226 concentrations often exceed the EPA limit. Other hotspots include the Carolinas Piedmont, the Texas Gulf Coast aquifer, and parts of the Rocky Mountain front.
Industrial sources are minor compared with the geological background, but legacy phosphate processing and oil-and-gas produced water can locally elevate radium in surface and shallow groundwater.
Cambrian-Ordovician sandstone
Major source across the Upper Midwest
Granite and shale aquifers
Decay product of natural uranium and thorium
Oil and gas produced water
Localized contamination near disposal sites
Phosphate processing waste
Historical contamination in parts of Florida
Find out for yourself
Is it in your water?
Public utilities test for combined radium (Ra-226 + Ra-228) under the EPA Radionuclides Rule and report results in their annual Consumer Confidence Report. Utilities in known hotspot regions often blend or treat to stay below the 5 pCi/L MCL.
Private well owners should test if they live in any of the documented hotspot regions, especially the Upper Midwest sandstone belt. State environmental health departments often subsidize radium testing, and certified labs run a combined Ra-226/Ra-228 panel for around $75 to $150. Results take several weeks because the analysis requires a long counting time.
The fix
How AquaOx filters it
Radium is one of the few radionuclides where the standard AquaOx system offers real filtration capability. Because radium chemically resembles calcium, it readily exchanges onto the resin in a standard cation-exchange water softener, the same mechanism that filters hardness. Studies by the EPA and state health departments confirm that a properly maintained softener typically filters 80% or more of radium.
Reverse osmosis at a point-of-use tap is also highly effective and is the better choice for drinking water in households with very elevated levels. For most affected wells, combining the AquaOx system with the under-sink RO covers both whole-house and drinking-water exposure.
Always test first to confirm radium activity and the relative contribution of Ra-226 versus Ra-228 before selecting treatment. Your state environmental health department is the right starting point.