1,4-dioxane
- Also known as
- dioxane, 1 4 dioxane
1,4-dioxane is a synthetic industrial chemical that can form as a trace byproduct when surfactants and other ingredients are made by ethoxylation. The U.S. EPA classifies it as likely to be carcinogenic to humans, and it is a persistent groundwater contaminant.
What is 1,4-dioxane?
1,4-dioxane is a colorless liquid that mixes readily with water. It has been used as an industrial solvent and as a stabilizer for chlorinated solvents. In consumer and cleaning products, the main concern is not deliberate use but trace contamination: 1,4-dioxane can form as a byproduct when ingredients are made by ethoxylation, the process that builds ethylene oxide chains onto molecules.
Where it is found
- Ethoxylated ingredients, including some surfactants such as sodium laureth sulfate and other ethoxylates used in cleaners, shampoos and cosmetics, at trace levels.
- Groundwater, where past industrial releases have created contamination. Because it mixes with water and resists breakdown, it spreads readily and is hard to remove.
Why it is a concern
The U.S. Environmental Protection Agency classifies 1,4-dioxane as likely to be carcinogenic to humans and has evaluated its risks under the Toxic Substances Control Act. California lists it under Proposition 65. Its persistence in water makes it a drinking water concern in affected areas.
Limits in products
Manufacturers reduce 1,4-dioxane in ethoxylated ingredients by removing it during processing, often by vacuum stripping. Some jurisdictions set legal limits: New York State, for example, has set maximum levels for 1,4-dioxane in household cleaning, personal care and cosmetic products. Many formulators also choose ingredients that are not ethoxylated, such as biosurfactants and other non-ethoxylated surfactants, to avoid the issue.
Frequently asked questions
Usually not intentionally. It is typically present as a trace byproduct of ethoxylation in some ingredients.
By using ingredients processed to remove it, or by choosing ingredients that are not made by ethoxylation.
Sources
- Technical fact sheet: 1,4-dioxane; risk evaluation under TSCA, U.S. Environmental Protection Agency
- Proposition 65 list, California Office of Environmental Health Hazard Assessment