1,4-Dioxane
1,4-Diethylene Dioxide · Dioxane
What it is
Not an intentional ingredient, a manufacturing byproduct formed during ethoxylation of surfactants (SLES, Alcohol Ethoxy Sulfate, C10-16 Alketh). Its presence cannot be detected from the label because it is never listed as an ingredient.
In this product: Manufacturing contaminant, no functional role. Formed as a byproduct when ‘-eth’ or ‘ethox’ ingredients are produced.
Dose & route, what actually matters
Dermal (skin residue on fabric against skin throughout the day); inhalation from VOCs released by warm clothes and drying; trace ingestion (hand-to-mouth, especially in children). 1,4-Dioxane can penetrate skin from certain formulations.
EUROPEAN UNION
No EU binding ppm limit for 1,4-dioxane in household cleaning products. REACH relies on raw material purity standards. EU SCCS Annex II prohibits 1,4-dioxane as a cosmetic ingredient but permits unavoidable trace impurities under Article 17. No specific ppm enforcement threshold equivalent to New York’s exists in the EU.
UNITED STATES
New York DEC Final Regulations (Subpart 352-1, adopted September 2024): 2 ppm limit for household cleansing products effective December 31, 2022; tightened to 1 ppm effective December 31, 2023. No federal limit. Pre-2024 independent testing found Tide at 3.67 ppm, Gain at 3.32 ppm, Arm & Hammer Clean Burst at 4.28 ppm, all above the NY 2 ppm limit. 2024 follow-up testing showed levels <1 ppm after reformulation.
The evidence
IARC classifies 1,4-dioxane as Group 2B (possibly carcinogenic to humans); EPA classifies it as a probable human carcinogen (Group B2). 2022 independent Bureau Veritas lab testing: Tide Original 3.67 ppm, Gain Original 3.32 ppm, Arm & Hammer Clean Burst 4.28 ppm, all above NY’s 2 ppm limit at time of test.
regulatory · 2022 · source
NY DEC finalized regulations (September 2024) setting a 1 ppm limit for 1,4-dioxane in household cleansing products, the only binding statutory limit for this contaminant in a US household product category.
regulatory · 2024 · source
California Prop 65: Listed on California Prop 65 as a known carcinogen. Products containing SLES and other -eth- surfactants may contain it as an unlabeled byproduct.
How to avoid it
Look for detergents with no ‘-eth-’ or ‘ethox’ surfactant names (SLES, Alcohol Ethoxy Sulfate, C10-16 Alketh). Brands that publish third-party 1,4-dioxane test results and those certified ‘free of 1,4-dioxane’ are the clearest options.
Where it hides
Editorial analysis of publicly available regulatory and peer-reviewed sources. Not medical advice. We name our evidence and link it, including when an ingredient is fine.