Hexachlorobenzene in drinking water
1,203 active public water systems in 37 states had a Hexachlorobenzene violation in the past three years, and 60 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 Hexachlorobenzene and lists the water systems whose records include a related violation. It does not show measured levels.
Is Hexachlorobenzene 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
Hexachlorobenzene (HCB) is a chlorinated aromatic compound formerly used as a fungicide on grain seeds and as an industrial chemical. All pesticide uses were canceled in the United States by 1984. It is also produced as a byproduct in the manufacture of certain chlorinated solvents and pesticides. HCB is highly persistent and bioaccumulates in fatty tissue and sediment.
Health effects
Chronic exposure to hexachlorobenzene is associated with liver damage, skin lesions, and neurological effects. EPA classifies it as a probable human carcinogen (Group B2). It can be transferred to infants through breast milk. Reproductive and developmental toxicity have been observed in animal studies.
The standard and what a violation means
EPA limit: 0.001 mg/L (1 ppb).
Water systems with a Hexachlorobenzene 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 | 200 | 3% | 8 |
| New York | 121 | 1% | 1 |
| Texas | 115 | 2% | 0 |
| Oklahoma | 97 | 8% | 0 |
| Oregon | 72 | 3% | 3 |
| Illinois | 62 | 1% | 12 |
| Washington | 44 | 1% | 8 |
| Colorado | 38 | 2% | 4 |
| Idaho | 37 | 2% | 4 |
| Montana | 37 | 2% | 1 |
| Connecticut | 31 | 1% | 1 |
| Utah | 29 | 3% | 1 |
| Michigan | 28 | 0% | 1 |
| Indiana | 27 | 1% | 2 |
| California | 26 | 0% | 1 |
| Alaska | 25 | 2% | 0 |
| Alabama | 25 | 4% | 0 |
| Wyoming | 24 | 3% | 1 |
| Vermont | 22 | 2% | 3 |
| Wisconsin | 18 | 0% | 0 |
| Missouri | 16 | 1% | 1 |
| Nevada | 16 | 3% | 0 |
| Arizona | 15 | 1% | 1 |
| North Carolina | 15 | 0% | 1 |
| Massachusetts | 12 | 1% | 1 |
| Maine | 11 | 1% | 0 |
| Rhode Island | 9 | 2% | 0 |
| Minnesota | 8 | 0% | 2 |
| New Jersey | 7 | 0% | 2 |
| Maryland | 3 | 0% | 1 |
| South Dakota | 3 | 0% | 0 |
| Virginia | 3 | 0% | 0 |
| North Dakota | 2 | 1% | 0 |
| New Mexico | 2 | 0% | 0 |
| Kentucky | 1 | 0% | 0 |
| Nebraska | 1 | 0% | 0 |
| New Hampshire | 1 | 0% | 0 |
Largest water systems with a Hexachlorobenzene 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 |
|---|---|---|---|---|
|
Denver Water Board Denver County |
1,287,000 | 3 | 0 | |
|
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 | |
|
Naperville Naperville · DuPage County |
156,406 | 1 | 0 | |
|
Epcor Agua Fria Surprise · Maricopa County |
128,040 | 5 | 0 | |
|
Pasco Water Department Franklin County |
115,102 | 2 | 0 | |
|
Inima USA / Aquaria LLC Dighton · Bristol County |
105,643 | 1 | 0 | |
|
Lehi City Utah County |
93,446 | 2 | 0 |
About this data
A system is counted once if any of its violations in the past three years involved Hexachlorobenzene, including monitoring and reporting lapses. Rules violated and status in the systems table are for the whole system, not Hexachlorobenzene 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.