1,4-Dioxane is a chemical contaminant that forms as an unintended byproduct during the manufacturing of common cleaning ingredients in laundry detergents. It is not added on purpose, and you won’t find it listed on any ingredient label. The EPA classifies it as a probable human carcinogen, which is why it has drawn attention from consumers and regulators alike.
How 1,4-Dioxane Ends Up in Detergent
Most laundry detergents rely on surfactants, the ingredients that actually lift dirt and grease off fabric. Many of these surfactants are made through a process called ethoxylation, where ethylene oxide is chemically bonded to fatty alcohols to make them better at dissolving in water. During one step of this process, particularly when the ethoxylated alcohol is treated with sulfuric or phosphoric acid, a side reaction produces 1,4-dioxane as a trace contaminant.
The most common surfactant involved is sodium laureth sulfate (SLES), one of the most widely used cleaning agents in both detergents and personal care products. The dioxane forms when unreacted sulfating agents trigger a chemical rearrangement in the ethoxylate chain. Other ethoxylated ingredients like polyethylene glycols (PEGs), polysorbates, and coceth compounds can also carry trace amounts of 1,4-dioxane, though typically at lower levels than SLES.
Because 1,4-dioxane is a manufacturing byproduct rather than an intentional ingredient, it never appears on product labels. This is the central frustration for consumers trying to avoid it.
Why It Raises Health Concerns
The EPA classifies 1,4-dioxane as a Group B2 probable human carcinogen, meaning animal studies have shown it causes cancer and there is supporting evidence suggesting risk to humans. In laboratory animals, chronic exposure through drinking water caused liver and kidney damage. High-level inhalation exposure in humans has caused dizziness, drowsiness, headaches, and irritation of the eyes, nose, and throat.
The concentrations found in a bottle of laundry detergent are far lower than those used in animal studies. Your exposure from a single wash cycle is small. The concern is cumulative: 1,4-dioxane shows up not just in detergent but in dish soap, shampoo, body wash, and other household products. When millions of households use these products daily, the compound also accumulates in the water supply, which creates a broader exposure pathway.
The Water Supply Problem
1,4-Dioxane is classified as a “persistent, mobile, and toxic” compound in the European Union’s chemical regulation framework. It resists biodegradation, moves freely through soil into groundwater, and is not effectively removed by standard wastewater or drinking water treatment processes. This combination of traits makes it especially problematic once it enters the environment.
Surveys have detected 1,4-dioxane in both drinking water and wastewater across all 50 U.S. states and in several European countries. Every load of laundry sends a small amount down the drain, and conventional treatment plants are not designed to break it down. Over time, the compound accumulates in drinking water sources, creating a low-level but persistent exposure route that goes beyond direct product contact.
How Manufacturers Reduce It
Most manufacturers now use a process called vacuum stripping to remove 1,4-dioxane from ethoxylated surfactants before formulating their products. This technique heats the surfactant under reduced pressure, causing the volatile dioxane to evaporate off. It is effective at bringing levels down significantly, though it does not eliminate the compound entirely. The degree of removal depends on how aggressively the stripping is performed, which varies by manufacturer.
Regulation Is Limited but Growing
There is no federal limit on 1,4-dioxane in household cleaning products in the United States. The most notable regulation comes from New York State, which passed a law setting a maximum allowable concentration of 2 parts per million (ppm) for household cleaning and personal care products as of December 31, 2022, tightening to 1 ppm as of December 31, 2023. This law pushed many manufacturers to reformulate or improve their stripping processes to meet the new threshold.
Outside of New York, most states have no specific limits on 1,4-dioxane in consumer products. Some states regulate it in drinking water, but the product itself remains largely unregulated at the federal level.
How to Spot It on a Label
You cannot find “1,4-dioxane” on an ingredient list because it is a contaminant, not a formulation ingredient. What you can look for are the ethoxylated ingredients most likely to carry it. The biggest red flags are ingredients with “eth” in the name or a number following the name, which indicates ethoxylation:
- Sodium laureth sulfate (SLES), the most common source, found in many conventional detergents
- Laureth, coceth, ceteareth, or deceth followed by a number (e.g., laureth-10, coceth-7)
- PEG compounds (e.g., PEG-100, PEG-40 stearate)
- Polysorbate-20 or polysorbate-80
- Any ingredient with “oxynol” in the name
The presence of these ingredients does not guarantee high dioxane levels. A well-manufactured product using vacuum stripping may contain negligible amounts. But if you want to minimize your exposure, these are the ingredient names to watch for.
Choosing Lower-Exposure Products
Detergents that avoid ethoxylated surfactants entirely will not contain 1,4-dioxane. Products built around plant-based soap compounds, coconut-derived surfactants that skip the ethoxylation step, or soap nuts naturally sidestep the issue. Some brands specifically market themselves as dioxane-free and use alternative cleaning agents like decyl glucoside or coco glucoside, which are made through a different chemical process that does not produce dioxane.
The EPA’s Safer Choice label is another useful shortcut. Products carrying this certification must meet strict ingredient standards, and the program evaluates contaminants like 1,4-dioxane as part of its review. Looking for third-party certifications like this is more reliable than trying to parse ingredient lists on your own, since the actual dioxane level depends on manufacturing quality rather than just which surfactant is used.