2,3,7,8-TCDD (Dioxin) in drinking water
354 active public water systems in 16 states had a 2,3,7,8-TCDD (Dioxin) violation in the past three years, and 21 have one that is still unresolved.
You are on Tapcensus, an independent guide to the EPA compliance records of every public water system in the United States. This page explains 2,3,7,8-TCDD (Dioxin) and lists the water systems whose records include a related violation. It does not show measured levels.
Is 2,3,7,8-TCDD (Dioxin) 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
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a chlorinated aromatic compound formed as a byproduct of industrial processes including waste incineration, herbicide manufacturing, and paper bleaching. It is not intentionally produced. TCDD is highly persistent in the environment and bioaccumulates in fatty tissue; drinking water is generally a minor exposure pathway compared to food.
Health effects
TCDD is classified as a known human carcinogen (Group A) by EPA. Even at extremely low concentrations it is associated with increased cancer risk, particularly soft tissue sarcoma and lymphoma. It also causes chloracne, liver damage, immune suppression, and reproductive and developmental toxicity. The MCL is set at a vanishingly low level reflecting its extreme potency.
The standard and what a violation means
EPA limit: 0.00000003 mg/L (0.03 ppt).
Water systems with a 2,3,7,8-TCDD (Dioxin) 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 | Unresolved |
|---|---|---|---|
| Pennsylvania | 233 | 3% | 13 |
| California | 26 | 0% | 1 |
| Alaska | 25 | 2% | 0 |
| Arizona | 14 | 1% | 1 |
| Massachusetts | 12 | 1% | 1 |
| Washington | 9 | 0% | 1 |
| New Jersey | 7 | 0% | 2 |
| Nevada | 7 | 1% | 0 |
| Minnesota | 5 | 0% | 2 |
| Oregon | 5 | 0% | 0 |
| Wisconsin | 5 | 0% | 0 |
| Idaho | 2 | 0% | 0 |
| Florida | 1 | 0% | 0 |
| Indiana | 1 | 0% | 0 |
| Kansas | 1 | 0% | 0 |
| Missouri | 1 | 0% | 0 |
Largest water systems with a 2,3,7,8-TCDD (Dioxin) 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 |
|---|---|---|---|---|
|
Pittsburgh Water & Sewer Auth Allegheny County |
520,000 | 3 | 0 | |
|
Gilbert, Town of Gilbert · Maricopa County |
247,600 | 9 | 1 | |
|
Corona, City of Corona · Riverside County |
169,380 | 6 | 0 | |
|
City of Sunnyvale Sunnyvale · Santa Clara County |
157,566 | 5 | 0 | |
|
Epcor Agua Fria Surprise · Maricopa County |
128,040 | 5 | 0 | |
|
Inima USA / Aquaria LLC Dighton · Bristol County |
105,643 | 1 | 0 | |
|
GW Santa Cruz Water CO Maricopa · Pinal County |
84,000 | 7 | 0 | |
|
Flagstaff City of Flagstaff · Coconino County |
79,796 | 5 | 0 | |
|
Capital Region Water Dauphin County |
66,540 | 1 | 0 | |
|
Lower Bucks CO Joint Mun Auth Bucks County |
63,007 | 1 | 0 |
About this data
A system is counted once if any of its violations in the past three years involved 2,3,7,8-TCDD (Dioxin), including monitoring and reporting lapses. Rules violated and status in the systems table are for the whole system, not 2,3,7,8-TCDD (Dioxin) 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.