CAREX Canada

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CAS No. 123-91-1

Photo: Wikimedia Commons^[1]

IARC Monograph Vol. 71, 1999 (Group 2B)

General Information

1,4-Dioxane is a clear colourless liquid^[2] with a faint, pleasant odour.^[3] 1,4-dioxane is a synthetic industrial chemical used as a stabilizer and a solvent.^[4] It may also be referred to as dioxane, 1,4-diethylene dioxide or diethylene oxide.^[5] There are numerous other synonyms and product names; see HSDB for more information.^[5]

1,4-Dioxane has been classified by IARC as Group 2B, possibly carcinogenic to humans, based on data in experimental animals.^[6] 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.^[6]

There is insufficient evidence to assess the carcinogenicity of 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.^[7]

Additional adverse health effects of dioxane exposure include liver and kidney damage, resulting from high levels of exposure.^[3] Eye and nose irritation has been reported from short term, low level exposure.^[3]

1,4-Dioxane has been ranked by CAREX Canada as Group A (immediate high priority) for occupational settings and as Group B (possible high priority) for environmental settings. Prioritization was based on the carcinogenicity and other toxic properties of the substance, the prevalence of exposure in Canada, and the feasibility of assessing exposure.

Regulations and Guidelines

Occupational Exposure Limits (OEL)

Canadian Jurisdictions	OEL (ppm)
Canada Labour Code	20 [sk]
BC, AB, MB, ON, QC, NL, PE, NS	20 [sk]
SK	20 [sk] 30 [stel]
YT	50 [sk, stel]
NT, NU	25 [sk] 100 [stel]
Other Jurisdiction	OEL (ppm)
ACGIH 2011 TLV	20 [sk]

ppm = parts per million

sk = easily absorbed through the skin

stel = short term exposure limit (15 min. maximum)

Canadian Environmental Guidelines

Jurisdiction	Limit	Year
Cosmetic Ingredients Hotlist	Not Permitted	2011^[11]

1,4-dioxane was not included in other Canadian government environmental guidelines reviewed.^[8,9,24]

Canadian Agencies/Organizations

Agency	Designation/Position	Year
Health Canada	DSL – high priority substance with the greatest potential for exposure	2006^[10]
Challenge to Industry	Batch 7 (Health)	2008^[13]

1,4-dioxane was not included in other Canadian government chemical listings reviewed.^[12]

Main Uses

Historically, 1,4-dioxane was used primarily (~90%) for the stabilization of a chemical called 1,1,1-trichloroethane (TCA).^[3] Since TCA use was limited in the US in 1996 due to its ozone-depleting properties, use of 1,4-dioxane for this purpose is no longer significant.^[3]

Currently, 1,4-dioxane is used as a laboratory reagent and as a solvent for the production of cellulose acetate, ethyl cellulose, benzyl cellulose, lacquers, plastics, varnishes, paints, dyes, resins, oils, fats, waxes, greases, polyvinyl polymers and for the pulping of wood.^[2] It has also been used as a chemical intermediate, polymerization catalyst, and an extraction medium, as well as in the production of plastics, rubber and pesticides.^[3]

1,4-Dioxane also has minor use as a working fluid for scintillation counter samples, in drug purification, as a spectroscopic-photometric solvent, a measuring tool for optical activity and as a manufacturing agent for membrane filters.^[5]

Canadian Production and Trade

The only data available regarding production and trade of 1,4-dioxane in Canada was collected from 1984-1986. At that time 15 industrial users reported that 2,010 tonnes had been manufactured, imported or were in commercial use during 1986.^[14]

Activity	Quantity	Year
Canadian Production	2,010 t	1986*^[14]
Export: N/A	None	2010^[16]
Import: N/A	None	2010^[16]

*last year on record

t = tonne

Occupational Exposures

Inhalation and dermal are both important routes of occupational exposure.^[17]

The main occupations exposed include workers involved in production, processing and use of 1,4-dioxane, as well as the production of plastics, paints, and cleaning chemicals.^[3] Individuals working in research and analytical science may also be exposed to dioxane in laboratories.^[3]

Past exposures of workers using TCA (with 1,4-dioxane as a stabilizer), such as in metal degreasing, were likely significant.^[3]

A European occupational exposure assessment developed models for three exposure scenarios including production of dioxane, formulation of products that contain dioxane, and end-use (either of dioxane itself or products containing it).^[17] 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 the formulation of products (i.e. adding dioxane, mixing and bagging of the final product) (typical concentration estimated at 40 mg/m³).

Environmental Exposures

Although little quantitative data is available 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.^[3]

1,4-dioxane in tap water may volatilize during showering, bathing and laundering, creating a source of exposure.^[3] 1,4-dioxane is soluble in water and can leach through soil into groundwater.^[3]

Residual levels of 1,4-dioxane may be found in consumer products including detergents, shampoos, cosmetics and pharmaceuticals.^[3] During manufacturing of these products, 1,4-dioxane can be formed as a by-product during condensing ethylene oxide or ethylene glycol.^[3] Although current practice is to remove 1,4-dioxane prior to addition of ethoxylated compounds, impurities may still be a concern.

Contamination of food may occur through either residues from packaging made from 1,4-dioxane-containing materials, or crops treated with pesticides containing 1,4-dioxane.^[2] However, since dioxane is not registered in Canada for use in pesticides either as an active ingredient or in any formulations,^[18.19] this is not likely to be a source of exposure.

Recent air monitoring data is not available. However, concentrations are expected to be higher near point sources.^[3]

Historically, 1,4-dioxane was rarely investigated during site assessments and remediation because past commercial analytical methods did not reliably detect the compound.^[20] Currently, there is a growing body of knowledge to address remediation and the EPA has classified 1,4-dioxane as an "Emerging Contaminant".^[4]

Sites typically contaminated with 1,4-dioxane include solvent release sites, and areas where wastewater is discharged from polyethylene terephthalate (PET) plastic manufacturing.^[4] PET was produced in Canada (forecasted to 2003) by 2 companies in Ontario.^[21]

Searches of environmental and consumer product databases yielded the following results on current potential for exposure to 1,4-dioxane in Canada:

NPRI and US Household Products Database

NPRI 2009^[22]
Search term: '1,4-dioxane'
Category	Quantity	Industry
Released into Environment	22 t	Resin and synthetic rubber manufactures and a basic chemical manufacturer (2 companies)
Disposed of	0.116 t
Sent to off-site recycling	None

US Household Products 2010^[23]
Search Term	Quantity	Product Type
'1,4-dioxane'	2	Adhesives