Industrial Chemicals– Possible Carcinogen (IARC 2B)
CAS No. 123-91-1
Photo: Wikimedia Commons
IARC Monograph Vol. 71, 1999 (Group 2B)
1,4-Dioxane is a clear and colourless liquid with a faint, pleasant odour. It is a synthetic industrial chemical used as a stabilizer and a solvent. It may also be referred to as dioxane, 1,4-diethylene dioxide, or diethylene oxide. There are numerous other synonyms and product names; see Hazardous Substances Data Bank (HSDB) for more information.
1,4-Dioxane is classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humans, based on data in experimental animals. When administered orally to mice, rats and guinea pigs, 1,4-dioxane produced increased incidences of tumours in a variety of sites including the skin, liver, nasal cavity, and mammary gland.
There is insufficient evidence to assess the carcinogenicity of 1,4-dioxane in humans. In a small occupational study between 1954 and 1975, mortality rates were not elevated in workers exposed to low concentrations of 1,4-dioxane.
Additional adverse health effects of exposure to 1,4-dioxane include liver and kidney damage, resulting from high levels of exposure. Eye and nose irritation is reported from short term, low level exposure.
1,4-dioxane was not included in other Canadian government environmental guidelines reviewed.[11,12,13,14,15,16]
DSL - high priority substance with the greatest potential for exposure
Challenge to Industry
Batch 7 (Health)
National Classification System for Contaminated Sites
Rank= "High hazard", potential human carcinogen
DSL = domestic substance list
1,4-dioxane was not included in other Canadian government chemical listings reviewed.
Historically, 1,4-dioxane was used to stabilize a chemical called 1,1,1-trichloroethane (TCA). TCA use was limited in the US in 1996 due to its ozone-depleting properties, making 1,4-dioxane use for this purpose no longer significant.
Currently, 1,4-dioxane is used as a laboratory reagent and as a solvent to produce cellulose acetate, ethyl cellulose, benzyl cellulose, lacquers, plastics, varnishes, paints, dyes, resins, oils, fats, waxes, greases, polyvinyl polymers, and wood pulp. It has also been used as a chemical intermediate, catalyst for polymerization, and an extraction medium, as well as in plastic, rubber, and pesticide production.
1,4-Dioxane also has a minor use as a working fluid for measuring radioactivity and optical activity, and purifying drugs. It can also act as a spectroscopic-photometric solvent and a manufacturing agent for membrane filters.
Canadian Production and Trade
10 - 100 t
t = tonne
Both inhalation and dermal contact are important routes of occupational exposure to 1,4-dioxane.
CAREX Canada estimates that approximately 3,600 Canadian are exposed to 1,4-dioxane in the workplace. The industry with the largest number of workers exposed to 1,4-dioxane is pharmaceutical and medicine manufacturing, followed by professional, scientific, and technical services. The largest occupational groups exposed are chemical technologists and technicians followed by chemists and chemical plant operators.
A European occupational exposure assessment developed models for three exposure scenarios including producing 1,4-dioxane, formulating products that contain it, and end-use (either of dioxane itself or products containing it). Dermal exposures were predicted to be highest during the use of dioxane-containing metal cleaning products (1.5 mg/cm2 skin/day). Estimates of inhalation exposure were highest during product formulation; for example adding 1,4-dioxane, and mixing and bagging the final product (typical concentration estimated at 40 mg/m3).
Although there is little quantitative data regarding levels of exposure to the general population, sources of 1,4-dioxane (in order of expected importance) are ambient and indoor air, drinking water, food, and dermal exposure from consumer products.
Recent air monitoring data is not available. However, concentrations are expected to be higher near point sources such as contaminated sites.
1,4-dioxane in tap water may volatilize during showering, bathing, and laundering, which creates a source of exposure. 1,4-dioxane is soluble in water and can leach through soil into groundwater.
Food may become contaminated through packaging made from 1,4-dioxane-containing materials, or crops treated with pesticides containing 1,4-dioxane.[2,25] However, since dioxane is not registered in Canada for use in pesticides either as an active ingredient or in any formulations,[26,27] this is not likely to be a source of exposure.
Residual levels of 1,4-dioxane may be found in consumer products including detergents, shampoos, cosmetics, and pharmaceuticals. During manufacturing of these products, 1,4-dioxane can be formed as a by-product when ethylene oxide or ethylene glycol are condensed. Although current practice is to remove 1,4-dioxane prior to adding ethoxylated compounds, impurities may still be a concern.
Historically, 1,4-dioxane was rarely investigated during site assessments and remediation because past methods of analysis did not reliably detect the compound. There is currently a growing body of knowledge to address remediation and the Environmental Protection Agency (EPA) has classified 1,4-dioxane as an "Emerging Contaminant".
Sites typically contaminated with 1,4-dioxane include solvent release sites, and areas where wastewater is discharged from polyethylene terephthalate (PET) plastic manufacturing. An internet product search yielded 31 suppliers of PET plastic and products in Canada.
Searches of environmental and consumer product databases yielded the following results on the potential for exposure to 1,4-dioxane in Canada:
NPRI and US Household Products Database
Search term: '1,4-Dioxane'
Released into Environment
Basic chemical manufacturing (2 facilities)
Sent to off-site recycling
US Household Products 2016
Adhesives & pet care:pesticidal shampoo
t = tonne
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposures Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. Click here to learn more about policies specific to 1,4-dioxane in the Directory. For questions about this resource, please contact a member of the Prevention Team at the Canadian Partnership Against Cancer at firstname.lastname@example.org.