Heptachlor Epoxide in drinking water
1,233 active public water systems in 38 states had a Heptachlor Epoxide violation in the past three years, and 63 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 Heptachlor Epoxide and lists the water systems whose records include a related violation. It does not show measured levels.
Is Heptachlor Epoxide 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
Heptachlor epoxide is the primary environmental metabolite of heptachlor, formed when heptachlor breaks down in soil, water, and biological tissue. Like its parent compound, it persists in the environment long after heptachlor use was discontinued. It is more toxic and more persistent than heptachlor itself and is detected independently in groundwater monitoring.
Health effects
Heptachlor epoxide is associated with liver damage and is classified by EPA as a probable human carcinogen (Group B2). It bioaccumulates in fatty tissue and can be transferred to infants through breast milk. Chronic low-level exposure is the primary concern in drinking water contexts.
The standard and what a violation means
EPA limit: 0.0002 mg/L (0.2 ppb).
Water systems with a Heptachlor Epoxide 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 | 201 | 3% | 8 |
| New York | 120 | 1% | 1 |
| Texas | 115 | 2% | 0 |
| Oklahoma | 96 | 7% | 0 |
| Oregon | 73 | 3% | 3 |
| Illinois | 58 | 1% | 12 |
| Washington | 44 | 1% | 8 |
| Colorado | 38 | 2% | 4 |
| Montana | 37 | 2% | 1 |
| Idaho | 36 | 2% | 3 |
| West Virginia | 32 | 4% | 4 |
| Connecticut | 31 | 1% | 1 |
| Utah | 29 | 3% | 1 |
| Indiana | 28 | 1% | 2 |
| Michigan | 28 | 0% | 1 |
| California | 26 | 0% | 1 |
| Alaska | 25 | 2% | 0 |
| Alabama | 25 | 4% | 0 |
| Wyoming | 24 | 3% | 1 |
| Vermont | 22 | 2% | 3 |
| North Carolina | 18 | 0% | 1 |
| Wisconsin | 18 | 0% | 0 |
| Missouri | 16 | 1% | 1 |
| Nevada | 16 | 3% | 0 |
| Arizona | 14 | 1% | 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 Heptachlor Epoxide 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 | |
|
Tucson City of Tucson · Pima County |
732,906 | 3 | 0 | |
|
Pittsburgh Water & Sewer Auth Allegheny County |
520,000 | 3 | 0 | |
|
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 Heptachlor Epoxide, including monitoring and reporting lapses. Rules violated and status in the systems table are for the whole system, not Heptachlor Epoxide 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.