Epichlorohydrin
C₃H₅ClO·Affects reproductive, liver
A residual monomer from epichlorohydrin-based polymers used as coagulants in water treatment and in epoxy resins lining pipes and tanks. IARC Group 2A probable human carcinogen. EPA regulates by Treatment Technique.
C₃H₅ClO
EPA limit
Treatment Technique (TT): polymer dose limit
Most at risk
Long-term consumers on municipal supplies using epi-amine polymer coagulants or epoxy-lined storage
Found in
City water · Industrial areas
AquaOx filters
YesActivated carbon
What it does to you
Health effects
Epichlorohydrin is classified by the IARC in Group 2A, probably carcinogenic to humans, based on consistent tumor formation in animal bioassays and on its mechanism of acting as a direct DNA alkylating agent. It is one of a small set of compounds that does not require metabolic activation to damage genetic material, which is part of why regulators treat it cautiously.
The most prominent non-cancer effects are reproductive toxicity and liver damage. Animal studies show reduced fertility and testicular effects at chronic exposure, and the compound is acutely irritating to skin, eyes, and the respiratory tract in workers handling it directly. Chronic exposure can also cause kidney damage and central nervous system effects.
The drinking water exposure route is residual unreacted epichlorohydrin monomer in epi-amine polymer coagulants and in epoxy resins lining water storage tanks and distribution piping. The polymer or resin itself is stable; the concern is the small fraction of free monomer that can leach into finished water.
Where it comes from
How it gets into your water
Epichlorohydrin is the building block for a family of polyamine coagulant polymers used in water and wastewater treatment, especially for color removal and clarification. It is also the basis of bisphenol A epoxy resins used to line steel water storage tanks, ductile-iron and steel water mains, and the interior of some galvanized pipe.
As with acrylamide, EPA addresses the residual monomer risk through a Treatment Technique rule rather than a numerical MCL. Utilities using epichlorohydrin-based polymers must certify that the polymer contains no more than 0.01% epichlorohydrin monomer when dosed at 20 mg/L of polymer. The same logic applies to epoxy linings: NSF/ANSI 61 certification limits the leachable epichlorohydrin from approved coatings.
Environmental discharge from epoxy resin manufacturing plants and from facilities producing glycerin via the epichlorohydrin route is a secondary source of contamination in some surface waters.
Polyamine coagulants
Epi-amine polymers used for clarification
Epoxy-lined tanks and mains
Leaching from cured epoxy coatings
Resin manufacturing
Industrial discharge from epoxy production
Glycerin manufacturing
Some routes use epichlorohydrin as intermediate
Find out for yourself
Is it in your water?
Like acrylamide, epichlorohydrin is regulated by Treatment Technique rather than by numerical MCL, so it does not appear as a concentration on most Consumer Confidence Reports. Utilities document compliance by certifying that any polymer used meets the EPA dose-and-purity limit, and that any epoxy coating in contact with water carries NSF/ANSI 61 certification.
Residual epichlorohydrin in finished water is generally very low, but the compound is a probable human carcinogen with no MCLG above zero. Long-term consumers wanting to reduce their cumulative exposure have a reasonable case for additional point-of-entry treatment.
The fix
How AquaOx filters it
Epichlorohydrin is filtered effectively by activated carbon. The coconut shell carbon stage in The AquaOx adsorbs epichlorohydrin as water passes through, in the same mechanism that captures other low-level industrial organics.
Because finished-water concentrations are already low when utilities comply with the Treatment Technique rule, the AquaOx role here is a polish: a second barrier between the treatment plant and the tap that reduces a probable carcinogen with no safe exposure target. Pair The AquaOx with the under-sink RO at the kitchen tap if you want maximum reduction on drinking and cooking water.