What is 1,4-Dioxane (CAS 123-91-1)? Safety, Regulation & EU/US/Canada Perspective

Sources: REACH SVHC Candidate List — European Chemicals Agency (ECHA) · last fetched 2026-06-07

1,4-Dioxane is a synthetic organic chemical compound with the molecular formula C4H8O2. It is a colorless liquid with a sweet, ether-like odor. 1,4-Dioxane is a byproduct of various industrial processes, including the production of ethylene glycol, a common ingredient in antifreeze and other chemicals.

What 1,4-Dioxane is

1,4-Dioxane is a cyclic ether, meaning that its molecular structure consists of a ring of five carbon atoms and two oxygen atoms. It is a volatile organic compound (VOC) and has been detected in various environmental media, including air, water, and soil.

Why regulators track it

Regulators track 1,4-Dioxane due to its potential health and environmental impacts. The International Agency for Research on Cancer (IARC) has classified 1,4-Dioxane as "possibly carcinogenic to humans" (Group 2B), based on evidence from animal studies. The European Chemicals Agency (ECHA) has listed 1,4-Dioxane on the REACH SVHC Candidate List, citing its carcinogenic properties as the reason. Substances on the SVHC Candidate List trigger ECHA notification and supplier-communication duties, and may later move to Annex XIV requiring authorisation.

European Union perspective

In the European Union, 1,4-Dioxane is regulated under the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) regulation (EC) No 1907/2006. The ECHA has listed 1,4-Dioxane on the REACH SVHC Candidate List (Candidate List of substances of very high concern identified for authorisation), citing its carcinogenic properties as the reason. The EU has also established a maximum allowable concentration of 0.1 mg/L for 1,4-Dioxane in drinking water (Directive 98/83/EC). The European Food Safety Authority (EFSA) has also established a tolerable daily intake (TDI) for 1,4-Dioxane of 0.3 mg/kg body weight per day.

United States perspective

In the United States, 1,4-Dioxane is regulated under the Toxic Substances Control Act (TSCA). The Environmental Protection Agency (EPA) has listed 1,4-Dioxane as a "chemical of concern" and has established a maximum allowable concentration of 1.0 mg/L for 1,4-Dioxane in drinking water (National Primary Drinking Water Regulations). The EPA has also established a reference dose (RfD) for 1,4-Dioxane of 0.3 mg/kg body weight per day. The California Office of Environmental Health Hazard Assessment (OEHHA) has also listed 1,4-Dioxane as a chemical known to the state to cause cancer (Proposition 65).

Canada perspective

In Canada, 1,4-Dioxane is regulated under the Canadian Environmental Protection Act (CEPA). Health Canada has listed 1,4-Dioxane as a toxic substance and has established a maximum allowable concentration of 0.1 mg/L for 1,4-Dioxane in drinking water (Guideline for Canadian Drinking Water Quality). The Canadian Environmental Assessment Agency (CEAA) has also listed 1,4-Dioxane as a substance of concern under the CEPA.

Where it shows up in consumer products

1,4-Dioxane is commonly found in personal care products, such as shampoos, conditioners, and body washes. It is also found in cleaning products, such as laundry detergents and dishwashing liquids. Additionally, 1,4-Dioxane has been detected in groundwater and surface water, as well as in soil and air.

If you think you have been exposed

If you think you have been exposed to 1,4-Dioxane, it is recommended that you consult a doctor, occupational health specialist, or poison control centre for advice. They can assess your exposure and provide guidance on any necessary medical treatment. You can also contact your local health authority or environmental agency for information on how to reduce your exposure to 1,4-Dioxane.

For more information on 1,4-Dioxane, please refer to the following sources:

• European Chemicals Agency (ECHA) - 1,4-Dioxane on the REACH SVHC Candidate List
• International Agency for Research on Cancer (IARC) - 1,4-Dioxane
• Environmental Protection Agency (EPA) - 1,4-Dioxane
• Health Canada - 1,4-Dioxane
• California Office of Environmental Health Hazard Assessment (OEHHA) - 1,4-Dioxane

Please note that this information is for general reference only and should not be considered as medical or legal advice. It is always recommended to verify the information on the primary register or with the relevant regulatory agency.

Verify on the primary regulator's register

• European Chemicals Agency (ECHA) — REACH SVHC Candidate List →
• CAS Common Chemistry — CAS 123-91-1 →
• ECHA chemical search (CAS 123-91-1) →

If you have an exposure concern

If you suspect acute exposure, contact your poison-control centre. For long-term concerns, speak with a occupational-health physician or your family doctor. ProductGuru does not provide medical advice.

• US National Poison Control (1-800-222-1222) →
• EU national poison centres (ECHA directory) →
• Canada provincial poison centres (CAPCC) →

Products tracked in ProductGuru that may contain this substance

• 3760100682717 — wiki view →
• 3760100680171 — wiki view →
• 3760100682779 — wiki view →
• 3760100682403 — wiki view →
• 3760100682649 — wiki view →

Same substance, other languages

• Deutsch →
• Français →

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