Radionuclides (Radium, Uranium, Gross Alpha)
Also known as: Radium-226/228, Uranium, Gross alpha, Radioactivity
Naturally radioactive elements that seep from rock into groundwater; a geology-driven, region-specific cancer risk.
Radium 5 pCi/L · Gross alpha 15 pCi/L · Uranium 30 µg/L. Radionuclides are naturally occurring radioactive elements regulated separately.
Long-term exposure increases cancer risk; uranium is also chemically toxic to the kidneys. Risks are chronic and dose-dependent.
Natural radioactive decay of uranium and thorium in rock and soil dissolves into groundwater. Concentrations follow geology — high in parts of the Central U.S., Mountain West, and Northeast.
Reverse osmosis, ion exchange, and lime softening remove radionuclides. Treatment generates low-level radioactive residuals that need careful disposal.
Source: EPA Safe Drinking Water Information System (SDWIS) · 2026 Q1
Radium, uranium, and gross-alpha radioactivity all come from the natural decay of elements in the earth's crust. Where groundwater moves through uranium- or radium-bearing rock, it picks up radioactivity that can exceed federal limits.
Like arsenic, radionuclide violations are a small-groundwater-system story concentrated in specific geological regions, where affordable treatment is the central challenge.
States with the most radionuclides violations
Community water systems with a related health-based violation since 2016.
| # | State | Systems |
|---|---|---|
| 1 | Texas | 118 |
| 2 | Colorado | 67 |
| 3 | Georgia | 55 |
| 4 | California | 49 |
| 5 | Minnesota | 43 |
| 6 | Missouri | 42 |
| 7 | Wisconsin | 36 |
| 8 | New Hampshire | 35 |
| 9 | Illinois | 33 |
| 10 | North Carolina | 31 |
| 11 | Oklahoma | 24 |
| 12 | New Jersey | 21 |
Common questions
What is the EPA limit for radionuclides in drinking water?
Radium 5 pCi/L · Gross alpha 15 pCi/L · Uranium 30 µg/L. Radionuclides are naturally occurring radioactive elements regulated separately.
Is radionuclides in drinking water dangerous?
Long-term exposure increases cancer risk; uranium is also chemically toxic to the kidneys. Risks are chronic and dose-dependent.
Where does radionuclides in water come from?
Natural radioactive decay of uranium and thorium in rock and soil dissolves into groundwater. Concentrations follow geology — high in parts of the Central U.S., Mountain West, and Northeast.
How do I remove radionuclides from my water?
Reverse osmosis, ion exchange, and lime softening remove radionuclides. Treatment generates low-level radioactive residuals that need careful disposal.
Which states have the most radionuclides violations?
Across U.S. community water systems, 791 have had a related health-based violation since 2016, led by Texas with 118.