What Is 1,4-Dioxane?
1,4-Dioxane is a synthetic industrial chemical classified by the EPA as a likely human carcinogen. Like PFAS, it is a long-lived industrial pollutant that resists conventional treatment and has been proposed for stricter EPA action but remains federally unregulated. It is a clear liquid with a faint pleasant odor, historically used as a stabilizer for chlorinated solvents (particularly 1,1,1-trichloroethane) and found as a trace contaminant in many consumer products including detergents, shampoos, and cosmetics. The EPA included 1,4-dioxane in UCMR 3 monitoring (2013–2015) to assess its presence in US drinking water.
1,4-Dioxane does not have a federal maximum contaminant level (MCL). The EPA established a health advisory level of 0.35 µg/L based on a one-in-10,000 excess cancer risk over a lifetime. Several states have set their own standards — notably, New York set a 1 µg/L MCL in 2020 and New Hampshire set 0.32 µg/L.
The compound is particularly concerning because it is highly mobile in groundwater, resistant to natural biodegradation, and difficult to remove with conventional water treatment. It passes through standard activated carbon filters and is not effectively removed by most common treatment technologies.
How 1,4-Dioxane Gets Into Drinking Water
1,4-Dioxane enters water supplies primarily through industrial contamination:
- Solvent stabilizer legacy: For decades, 1,4-dioxane was added to chlorinated solvents used in degreasing operations. When these solvents were improperly disposed of, 1,4-dioxane migrated into groundwater
- Landfill leachate: Municipal and industrial landfills containing products with 1,4-dioxane residues leach the compound into surrounding groundwater
- Wastewater discharge: Municipal wastewater treatment plants that receive industrial wastewater can discharge 1,4-dioxane to surface water, as conventional treatment does not remove it
- Superfund and contaminated sites: The EPA has identified 1,4-dioxane at over 30 Superfund National Priorities List sites
Unlike many organic contaminants, 1,4-dioxane does not bind to soil particles and moves freely with groundwater, creating large contamination plumes that can extend miles from the source.
Health Effects
Cancer Risk
The EPA classifies 1,4-dioxane as a likely human carcinogen based on:
- Liver tumors in multiple animal species (rats and mice) exposed through drinking water
- Nasal tumors in rats exposed via inhalation
- Kidney tumors observed in some animal studies
The 0.35 µg/L health advisory is based on a 1-in-10,000 excess cancer risk model. This means that at that concentration, one additional cancer case per 10,000 people exposed over a lifetime would be expected.
Other Health Effects
- Liver damage: The liver is the primary target organ. Chronic exposure causes fatty liver changes, cellular damage, and at high doses, liver tumors
- Kidney effects: Kidney toxicity has been observed in animal studies at moderate to high exposure levels
- Eye and respiratory irritation: At high concentrations (primarily occupational exposure), 1,4-dioxane causes irritation of the eyes, nose, and throat
EPA Regulation Status
1,4-Dioxane does not have a federal MCL. After UCMR 3 monitoring, the EPA placed it on the Contaminant Candidate List but has not yet proposed a regulation. The 0.35 µg/L health advisory is non-enforceable guidance. State-level standards vary significantly:
- New York: 1 µg/L MCL (enforceable)
- New Hampshire: 0.32 µg/L (enforceable)
- Several other states have notification or action levels between 0.25 and 7.2 µg/L
How to Remove 1,4-Dioxane from Drinking Water
1,4-Dioxane is one of the most difficult contaminants to remove from water:
- Advanced oxidation processes (AOP): The most effective municipal treatment, using UV light combined with hydrogen peroxide to break down the compound
- Reverse osmosis (RO): Point-of-use RO systems can reduce levels, though removal efficiency varies (typically 60–90%)
- Distillation: Effective for small volumes
Standard treatment methods that are NOT effective against 1,4-dioxane:
- Granular activated carbon (GAC) — 1,4-dioxane passes through
- Standard carbon block filters and pitcher filters
- Air stripping (1,4-dioxane has low volatility)
- Conventional coagulation/flocculation
If your water contains 1,4-dioxane above the health advisory, a reverse osmosis system is the most practical point-of-use option — see our guide to the best reverse osmosis systems. Households on private wells near industrial sites should also see private wells and PFAS, which covers the same testing and treatment patterns that apply to 1,4-dioxane.
Frequently Asked Questions
Is 1,4-dioxane common in drinking water?
UCMR 3 data (2013–2015) detected 1,4-dioxane in about 21% of public water systems tested, though most detections were at very low levels. Systems near industrial areas, landfills, or Superfund sites have the highest risk. About 7% of tested systems had levels above the 0.35 µg/L health advisory.
Can I filter 1,4-dioxane from my tap water?
Standard pitcher or faucet-mount carbon filters do not remove 1,4-dioxane. A reverse osmosis (RO) system is the most effective point-of-use option, typically removing 60–90% of the compound. For municipal treatment, advanced oxidation processes (UV + hydrogen peroxide) are required.
Does boiling water remove 1,4-dioxane?
No. Boiling does not remove 1,4-dioxane and may slightly concentrate it by reducing water volume. Reverse osmosis is recommended for home treatment.