Radium-226 in drinking water
401 active public water systems in 23 states had a Radium-226 violation in the past three years, and 23 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 Radium-226 and lists the water systems whose records include a related violation. It does not show measured levels.
Is Radium-226 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.
Enter a ZIP code, town, or street address.
What it is and where it comes from
Radium-226 is a naturally occurring alpha-emitting radioactive isotope in the uranium-238 decay chain. It dissolves from uranium-bearing bedrock into groundwater and is more prevalent in deep, older aquifers. Wells in granite-rich geology can carry detectable radium-226 levels. It is regulated individually as well as jointly with radium-228.
Health effects
Radium-226 accumulates in bone tissue and delivers a sustained alpha radiation dose internally. Long-term exposure increases risk of bone cancer, and historic occupational data from radium dial painters established the carcinogenic mechanism. Children absorb more radium due to active bone growth, making them most vulnerable to skeletal radiation effects.
The standard and what a violation means
EPA limit: 5 pCi/L (when measured individually; combined Ra-226 + Ra-228 MCL also applies).
Water systems with a Radium-226 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 |
|---|---|---|---|
| Pennsylvania | 123 | 2% | 3 |
| Indiana | 48 | 1% | 0 |
| New Jersey | 39 | 1% | 1 |
| Utah | 31 | 3% | 4 |
| New York | 27 | 0% | 0 |
| Idaho | 21 | 1% | 3 |
| Wyoming | 19 | 2% | 2 |
| Wisconsin | 17 | 0% | 6 |
| Alabama | 13 | 2% | 0 |
| North Carolina | 10 | 0% | 1 |
| Vermont | 8 | 1% | 0 |
| Arizona | 7 | 0% | 1 |
| Missouri | 7 | 0% | 0 |
| Tennessee | 6 | 1% | 0 |
| Nevada | 5 | 1% | 0 |
| Massachusetts | 4 | 0% | 0 |
| Michigan | 4 | 0% | 0 |
| Montana | 4 | 0% | 1 |
| South Dakota | 3 | 0% | 0 |
| North Dakota | 2 | 1% | 0 |
| California | 1 | 0% | 0 |
| Ohio | 1 | 0% | 0 |
| Rhode Island | 1 | 0% | 1 |
Largest water systems with a Radium-226 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 | |
|
Corona, City of Corona · Riverside County |
169,380 | 6 | 0 | |
|
GW Santa Cruz Water CO Maricopa · Pinal County |
84,000 | 7 | 0 | |
|
Fairhope, City of Fairhope · Baldwin County |
59,850 | 1 | 0 | |
|
Perth Amboy Water Department Perth Amboy City · Middlesex County |
52,328 | 2 | 0 | |
|
Tooele City Water System Tooele County |
41,770 | 2 | 0 | |
|
South Alabama Utilities Water System Citronelle · Mobile County |
39,249 | 3 | 0 | |
|
Winslow Twp Dmu Winslow Twp · Camden County |
39,174 | 6 | 0 | |
|
Aqua NJ Hamilton Square Hamilton Twp · Mercer County |
39,128 | 4 | 2 | |
|
Bullhead City Mohave Bullhead City · Mohave County |
36,330 | 13 | 1 |
About this data
A system is counted once if any of its violations in the past three years involved Radium-226, including monitoring and reporting lapses. Rules violated and status in the systems table are for the whole system, not Radium-226 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.