Thallium in U.S. Drinking Water
Health-based violation data for Thallium from EPA Safe Drinking Water Information System (SDWIS). Covers all community water systems with violations on record.
Thallium has been found in violation of EPA standards in 84 water systems across 10 states, with 638 total health-based violations recorded. The most affected states are Nebraska, Texas, California.
Thallium is regulated under the EPA Safe Drinking Water Act, which sets enforceable Maximum Contaminant Levels (MCLs) and associated treatment technique requirements for public water systems. The EPA Safe Drinking Water Information System (SDWIS) tracks every recorded violation nationwide and links it back to the specific public water system (PWSID), violation type, and begin date.
Across the United States, SDWIS records show 638 health-based violations for Thallium affecting 84 community water systems in 10 states. Violation counts cluster heaviest in Nebraska, Texas, California, with Nebraska alone accounting for 139 violations across 32 systems. The contaminant is listed on the federal primary drinking water regulations.
A health-based violation does not mean residents were necessarily harmed, it means the contaminant exceeded the federal MCL in a compliance sample, triggering notification and remediation requirements. States and utilities maintain primary enforcement responsibility. To check the status of a specific water system, request its most recent Consumer Confidence Report or consult the EPA's Drinking Water Watch portal for the corresponding state.
Violations by State
States ranked by number of health-based violations for Thallium.
| # | State | Violations | Systems Affected |
|---|---|---|---|
| 1 | Nebraska | 139 | 32 |
| 2 | Texas | 131 | 5 |
| 3 | California | 102 | 8 |
| 4 | New Mexico | 56 | 2 |
| 5 | Kansas | 49 | 6 |
| 6 | Arizona | 46 | 1 |
| 7 | Colorado | 16 | 2 |
| 8 | Iowa | 16 | 1 |
| 9 | Oklahoma | 15 | 8 |
| 10 | South Dakota | 8 | 1 |
Most Affected Water Systems
Top 50 water systems by number of Thallium health-based violations.
Frequently Asked Questions
Is Thallium in my water?
Thallium has been detected in violation of EPA health standards in 84 water systems across 10 states. To check your specific utility, look up your annual Consumer Confidence Report (CCR) - water systems are required to disclose all violations.
How many water systems have Thallium violations?
EPA SDWIS records show 84 community water systems with health-based Thallium violations, totaling 638 violations. These represent cases where the contaminant exceeded the EPA Maximum Contaminant Level (MCL).
Which states have the most Thallium violations?
The states with the most Thallium violations are: Nebraska (139 violations), Texas (131 violations), California (102 violations), New Mexico (56 violations), Kansas (49 violations).
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About This Data
Violation data is from the EPA Safe Drinking Water Information System (SDWIS). Only health-based violations are shown, these include Maximum Contaminant Level (MCL) and Treatment Technique (TT) violations. Monitoring and reporting violations are excluded. Data may not reflect the most current enforcement actions.
Source: U.S. Environmental Protection Agency, SDWIS Federal Reporting Services U.S. Environmental Protection Agency, SDWIS Federal Reporting Services
Read our methodology - how this data is sourced, computed, and verified.