Heptachlor Epoxide
Heptachlor Epoxide·Affects liver, reproductive
The breakdown product of the banned insecticide heptachlor. More persistent than the parent compound and the dominant residue found in soil, groundwater, and human tissue.
Heptachlor Epoxide
EPA limit
0.0002 mg/L (MCL)
Most at risk
Residents of pre-1988 termite-treated homes, rural well-water households in former application areas
Found in
City water · Well water
AquaOx filters
YesActivated coconut shell carbon
What it does to you
Health effects
Heptachlor epoxide is classified by the EPA as a probable human carcinogen, with the same regulatory weight as the parent compound heptachlor. Long-term animal studies show liver tumors, and epidemiological studies have associated chronic exposure with elevated rates of cancer and adverse reproductive outcomes.
The compound is more persistent than heptachlor itself, both in the environment and in human tissue. It bioaccumulates in fatty tissue, crosses the placenta, and is excreted in breast milk, so exposure can persist long after contact with the parent compound ends.
Chronic exposure damages the liver, disrupts reproductive hormones, and is linked to developmental effects in animals exposed in utero. The EPA sets the MCL for heptachlor epoxide (0.2 ppb) lower than for heptachlor itself (0.4 ppb) because of its greater persistence.
Where it comes from
How it gets into your water
Heptachlor epoxide is not applied directly. It forms in soil and groundwater as the parent compound heptachlor breaks down, and it is more persistent than heptachlor itself, so it builds up over time and becomes the dominant residue in legacy-contaminated water.
Homes treated for termites before 1988 often have measurable heptachlor epoxide in foundation soil and shallow groundwater. Agricultural fields treated for corn and citrus pests in past decades also continue to contribute, particularly where the original heptachlor has had time to degrade.
All current detections are from legacy contamination working through the hydrologic cycle.
Termite-treated foundations
Forms from pre-1988 heptachlor applications
Legacy crop fields
Breakdown product of heptachlor in soil
Shallow groundwater
Persistent in former-use regions
Find out for yourself
Is it in your water?
Public utilities test for heptachlor epoxide and report results in their annual Consumer Confidence Report. The compound is typically detected together with heptachlor, with the epoxide at higher levels in older contamination.
If your home was built before 1988 and treated for termites, or if your well is in a region with historical agricultural use, you should test for both heptachlor and heptachlor epoxide as part of a broader cyclodiene insecticide panel.
The fix
How AquaOx filters it
Heptachlor epoxide is filtered efficiently by activated carbon. The coconut shell carbon stage in The AquaOx adsorbs heptachlor epoxide molecules as water passes through, with independent testing showing reductions above 95%.
For well-water households near former application sites, we recommend pairing The AquaOx with our FE Edition or RE Edition if iron or hydrogen sulfide is also present, and adding the under-sink RO for additional drinking-water polish.