Combined Radium (-226 and -228) in drinking water
970 active public water systems in 38 states had a Combined Radium (-226 and -228) violation in the past three years, and 96 had one in the latest quarter of EPA's data.
You are on Tapcensus, an independent guide to the EPA compliance records of every public water system in the United States. This page explains Combined Radium (-226 and -228) and lists the water systems whose records include a related violation. It does not show measured levels.
Is Combined Radium (-226 and -228) in the records for your water system?
Enter a ZIP code, town, or street address to see the water systems that serve your area, their status, and which rules and contaminants appear in their violations.
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What it is and where it comes from
Radium-226 and Radium-228 are naturally occurring radioactive isotopes produced by the decay of uranium and thorium in bedrock. They dissolve into groundwater, particularly in deep aquifers with low oxygen and low pH. Granite bedrock and some deep sandstone and limestone aquifers present conditions where combined radium can reach detectable levels in drinking water.
Health effects
Radium is a bone-seeking radionuclide that accumulates in skeletal tissue after ingestion. Long-term exposure increases the risk of bone cancer and leukemia. There is no safe threshold for ionizing radiation — the MCL is set at a level balancing risk reduction with treatment feasibility. Children are particularly vulnerable due to higher rates of bone growth and calcium uptake.
The standard and what a violation means
EPA limit: 5 pCi/L (combined Ra-226 and Ra-228).
Water systems with a Combined Radium (-226 and -228) violation, by state
Active public water systems that reported at least one related violation to EPA in the past three years. Each state links to the list of its affected systems.
| State | Systems with violations, 3 yr | Share of active systems | In violation, latest quarter |
|---|---|---|---|
| Oregon | 132 | 5% | 9 |
| Oklahoma | 112 | 9% | 0 |
| Georgia | 102 | 4% | 7 |
| Illinois | 76 | 1% | 11 |
| Colorado | 67 | 3% | 26 |
| Texas | 66 | 1% | 0 |
| New Jersey | 42 | 1% | 5 |
| Alaska | 37 | 3% | 1 |
| Wisconsin | 31 | 0% | 9 |
| Iowa | 25 | 1% | 3 |
| Maine | 25 | 1% | 0 |
| North Carolina | 25 | 0% | 4 |
| New York | 25 | 0% | 0 |
| Virginia | 25 | 1% | 1 |
| Michigan | 21 | 0% | 0 |
| Minnesota | 20 | 0% | 5 |
| Wyoming | 19 | 2% | 2 |
| Montana | 16 | 1% | 1 |
| Arizona | 15 | 1% | 4 |
| California | 13 | 0% | 2 |
| Washington | 13 | 0% | 1 |
| Connecticut | 10 | 0% | 1 |
| Missouri | 7 | 0% | 1 |
| South Dakota | 7 | 1% | 0 |
| New Hampshire | 6 | 0% | 0 |
| Nevada | 6 | 1% | 0 |
| Vermont | 5 | 0% | 1 |
| Florida | 4 | 0% | 0 |
| North Dakota | 4 | 1% | 0 |
| New Mexico | 4 | 0% | 0 |
| Utah | 3 | 0% | 1 |
| Arkansas | 1 | 0% | 0 |
| Delaware | 1 | 0% | 0 |
| Idaho | 1 | 0% | 0 |
| Kansas | 1 | 0% | 0 |
| Maryland | 1 | 0% | 0 |
| Pennsylvania | 1 | 0% | 1 |
| South Carolina | 1 | 0% | 0 |
Largest water systems with a Combined Radium (-226 and -228) violation
The ten biggest systems, by people served, whose records include a related violation in the past three years.
| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
Tucson City of Tucson · Pima County |
732,906 | 3 | 0 | |
|
Joliet Joliet · Will County |
160,000 | 4 | 0 | |
|
Albany Albany · Dougherty County |
101,245 | 2 | 0 | |
|
Aqua WSC Bastrop County |
86,325 | 5 | 1 | |
|
GW Santa Cruz Water CO Maricopa · Pinal County |
84,000 | 7 | 0 | |
|
Waukesha Water Utility Waukesha · Waukesha County |
70,718 | 2 | 1 | |
|
East Cherry Creek Valley Wsd Arapahoe County |
66,130 | 1 | 0 | |
|
Moore Public Works Authority Cleveland County |
55,083 | 4 | 0 | |
|
Edina Hennepin County |
53,494 | 1 | 0 | |
|
Perth Amboy Water Department Perth Amboy City · Middlesex County |
52,328 | 2 | 0 |
About this data
A system is counted once if any of its violations in the past three years involved Combined Radium (-226 and -228), including monitoring and reporting lapses. Rules violated and status in the systems table are for the whole system, not Combined Radium (-226 and -228) alone. Counts cover active systems in all 50 states and the District of Columbia.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet.