Hexachlorobenzene
C₆Cl₆·Affects liver, kidneys, reproductive
A banned fungicide and persistent organic pollutant. Bioaccumulates in fatty tissue and remains in the environment for decades after release.
C₆Cl₆
EPA limit
0.001 mg/L (MCL)
Most at risk
Households near former agricultural use areas, chlor-alkali plants, or chemical manufacturing sites
Found in
City water · Well water · Industrial areas
AquaOx filters
YesActivated coconut shell carbon
What it does to you
Health effects
Hexachlorobenzene (HCB) is a persistent organic pollutant that primarily targets the liver, kidneys, and reproductive system. Chronic exposure causes liver damage, porphyria (a metabolic disorder), and immune system suppression. A historical poisoning incident in Turkey in the 1950s, when seed grain treated with HCB was eaten by humans, established its toxicity at high doses.
The International Agency for Research on Cancer classifies HCB as Group 2B (possibly carcinogenic to humans). Animal studies show liver, kidney, and thyroid tumors at sustained exposure. The EPA classifies HCB as a probable human carcinogen.
HCB is highly lipophilic and bioaccumulates in fatty tissue. It crosses the placenta and is excreted in breast milk, with documented developmental effects in offspring of exposed mothers. The MCL of 1 microgram per liter reflects both cancer and non-cancer endpoints.
Where it comes from
How it gets into your water
HCB was registered as a fungicide for seed treatment in the United States until 1984, when it was banned. The compound persists in soil and groundwater for decades after release, so legacy agricultural contamination remains a source today.
Current contamination pathways include unintentional production as a byproduct in the manufacture of chlorinated solvents, pesticides, and chlor-alkali chemicals. Atmospheric deposition from industrial combustion and waste incineration distributes HCB globally, including to remote ecosystems. The Stockholm Convention on Persistent Organic Pollutants lists HCB as a priority chemical for elimination.
Chemical manufacturing
Byproduct of chlorinated chemicals
Former pesticide use
Legacy seed treatment contamination
Contaminated wells
Near agricultural or industrial sites
Waste incineration
Atmospheric deposition
Find out for yourself
Is it in your water?
Public water utilities are required to test for hexachlorobenzene and report results in the annual Consumer Confidence Report. Most municipal supplies report non-detect because of the low ambient concentrations and the compound's tendency to bind soil rather than stay dissolved in water.
Private well owners near former agricultural areas where HCB-treated seed was used, chlor-alkali plants, chlorinated pesticide manufacturers, or waste incinerators should request a chlorinated pesticide or VOC panel that includes HCB. EPA Method 525 detects HCB at sub-microgram-per-liter levels.
The fix
How AquaOx filters it
Activated carbon is the EPA's recommended best-available technology for filtering hexachlorobenzene from drinking water. The Centaur catalytic carbon and coconut shell activated carbon stages in The AquaOx adsorb HCB strongly because of its highly hydrophobic, chlorinated structure that binds tightly to carbon surfaces.
For households with confirmed HCB contamination, we recommend pairing The AquaOx with the under-sink RO at the kitchen tap for a second-stage barrier on drinking and cooking water.
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