Arsenic in U.S. Drinking Water
Health-based violation data for Arsenic from EPA Safe Drinking Water Information System (SDWIS). Covers all community water systems with violations on record.
Arsenic has been found in violation of EPA standards in 2,216 water systems across 45 states, with 12,012 total health-based violations recorded. The most affected states are California, Alaska, Oklahoma.
Arsenic 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 12,012 health-based violations for Arsenic affecting 2,216 community water systems in 45 states. Violation counts cluster heaviest in California, Alaska, Oklahoma, with California alone accounting for 1,249 violations across 162 systems. EPA health-effect summaries describe the specific exposure concerns that drove the federal standard.
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.
What are the health effects of this contaminant?
Arsenic is a naturally occurring contaminant that, with long-term exposure above EPA limits, is linked to skin damage, circulatory problems, and increased cancer risk.
Source: U.S. Environmental Protection Agency. Consult your doctor for personalized health guidance U.S. Environmental Protection Agency. Consult your doctor for personalized health guidance
Violations by State
States ranked by number of health-based violations for Arsenic.
| # | State | Violations | Systems Affected |
|---|---|---|---|
| 1 | California | 1,249 | 162 |
| 2 | Alaska | 1,049 | 79 |
| 3 | Oklahoma | 783 | 73 |
| 4 | Colorado | 626 | 101 |
| 5 | Oregon | 457 | 65 |
| 6 | Washington | 403 | 37 |
| 7 | New York | 315 | 142 |
| 8 | Arkansas | 309 | 29 |
| 9 | Pennsylvania | 302 | 74 |
| 10 | Puerto Rico | 167 | 102 |
| 11 | Louisiana | 133 | 9 |
| 12 | Iowa | 97 | 11 |
| 13 | Montana | 82 | 22 |
| 14 | Idaho | 72 | 21 |
| 15 | New Jersey | 70 | 20 |
| 16 | Arizona | 65 | 11 |
| 17 | Texas | 52 | 13 |
| 18 | West Virginia | 51 | 15 |
| 19 | Utah | 47 | 15 |
| 20 | New Mexico | 34 | 13 |
| 21 | Massachusetts | 25 | 13 |
| 22 | Tennessee | 24 | 9 |
| 23 | Kansas | 22 | 4 |
| 24 | Ohio | 21 | 8 |
| 25 | Connecticut | 20 | 11 |
| 26 | Missouri | 19 | 6 |
| 27 | Nebraska | 18 | 6 |
| 28 | Wyoming | 18 | 9 |
| 29 | Virginia | 16 | 10 |
| 30 | Vermont | 15 | 14 |
| 31 | Hawaii | 12 | 8 |
| 32 | New Hampshire | 12 | 4 |
| 33 | Maine | 11 | 6 |
| 34 | North Carolina | 11 | 5 |
| 35 | District of Columbia | 9 | 1 |
| 36 | Michigan | 9 | 3 |
| 37 | South Carolina | 9 | 2 |
| 38 | Georgia | 8 | 3 |
| 39 | Florida | 7 | 2 |
| 40 | Indiana | 6 | 3 |
| 41 | Maryland | 6 | 6 |
| 42 | Nevada | 6 | 5 |
| 43 | South Dakota | 2 | 1 |
| 44 | Rhode Island | 1 | 1 |
| 45 | American Samoa | 1 | 1 |
Most Affected Water Systems
Top 50 water systems by number of Arsenic health-based violations.
Frequently Asked Questions
Is Arsenic in my water?
Arsenic has been detected in violation of EPA health standards in 2,216 water systems across 45 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 Arsenic violations?
EPA SDWIS records show 2,216 community water systems with health-based Arsenic violations, totaling 12,012 violations. These represent cases where the contaminant exceeded the EPA Maximum Contaminant Level (MCL).
Which states have the most Arsenic violations?
The states with the most Arsenic violations are: California (1,249 violations), Alaska (1,049 violations), Oklahoma (783 violations), Colorado (626 violations), Oregon (457 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.