1,4-Dioxane is an unintentional manufacturing contaminant generated during the ethoxylation process used to make surfactants in foaming cleaning products and shampoos. It is not an added ingredient and will not appear on any label — yet it is present in many popular dish soaps, laundry detergents, and bathroom cleaners at levels that pose a measurable cancer risk according to US EPA assessments. It is a probable human carcinogen that is both waterborne and volatilises during product use.
Where it's found
Dish soaps and washing-up liquids containing sodium laureth sulphate (SLES) or other ethoxylated surfactants (PEG compounds, ingredients ending in -eth) are the primary domestic source. Laundry detergents using ethoxylated surfactants. Shampoos and body washes. Bathroom and kitchen spray cleaners. 1,4-Dioxane is not listed on labels because it is a process contaminant generated during manufacture, not an intentionally added ingredient. Surveys by the Campaign for Safe Cosmetics and US consumer organisations have found 1,4-dioxane in widely used supermarket products at concentrations ranging from trace levels to over 100 ppm.
Routes of exposure
Dermal absorption during dishwashing, bathing, and hand cleaning. Inhalation from volatilisation during hot water dishwashing and showering — 1,4-dioxane is volatile and concentrates in poorly ventilated bathrooms and kitchens during product use. Potential oral ingestion via hand-to-mouth contact, particularly relevant for young children. Environmental exposure through contaminated drinking water near industrial sites — 1,4-dioxane is highly water-soluble, persistent, and not removed by conventional water treatment.
Health concerns
1,4-Dioxane is classified by the IARC as a Group 2B possible human carcinogen. In rodents it causes liver and nasal tumours. US EPA classifies it as a probable human carcinogen (Group B2) and has set a reference concentration for inhalation. A 2018 New York State Department of Health survey found 1,4-dioxane in 63% of children's personal care products and 82% of laundry detergents tested. California Proposition 65 lists 1,4-dioxane as a known carcinogen since 1988. The risk is particularly concerning because it is invisible to consumers — there is no label disclosure and no practical way to identify affected products without independent laboratory testing.
Evidence
Carcinogenicity in rodents is well established. IARC Group 2B classification reflects adequate animal evidence and limited human data. The key uncertainty is the dose–response at domestic exposure levels — rodent studies used high doses, and extrapolating to human risk from product use involves assumptions about skin absorption and inhalation rates. Independent laboratory surveys consistently detect 1,4-dioxane in consumer products at concentrations above thresholds of concern calculated from EPA risk assessments.
Who's most at risk
Infants and young children using baby wash and shampoo products containing ethoxylated surfactants have the highest relative exposure. Frequent users of foaming cleaning products with intensive skin contact — professional cleaners, food service workers washing up repeatedly — have elevated occupational dermal and inhalation exposure.
Regulatory status
RegulationThere is no mandatory limit for 1,4-dioxane in cleaning products in the EU, UK, or US. New York State enacted a limit of 2 ppm for cleaning products (effective 2023) — the first US state to do so. The EU and UK allow manufacturers to self-regulate by limiting the contaminant through manufacturing process controls, but compliance is voluntary and not consistently monitored. The FDA has recommended but not required removal from cosmetics.
How to reduce your exposure
Choose cleaning and personal care products that do not contain ingredients ending in -eth (sodium laureth sulphate, PEG-80, laureate-7, ceteareth) — ethoxylated ingredients are the source of 1,4-dioxane contamination. Products certified by COSMOS, EWG Verified, or similar schemes typically have low or absent 1,4-dioxane. Bar soap instead of liquid soap avoids ethoxylated surfactants entirely. Vacuum strip in manufacturing (used by some manufacturers) removes residual 1,4-dioxane — choose brands that disclose this.
The nutrition connection
The 1,4-dioxane issue underscores a broader point about transparency in ingredient sourcing: a product can contain no intentionally harmful additives yet still carry a carcinogenic contaminant from its manufacturing process. Label literacy — identifying ethoxylated ingredients by their -eth suffix — is one of the most practical tools available to consumers navigating cleaning product safety without access to laboratory data. Choosing soap bars and simple formulations with short ingredient lists reduces the likelihood of ethoxylated surfactant contamination across multiple product categories.