1,4-Dioxane

1,4-Dioxane (C₄H₈O₂, CAS No. 123-91-1) also can be identified as dioxane, dioxan, p-dioxane, diethylene dioxide, diethylene oxide, diethylene ether, or glycol ethylene ether.

A colorless, flammable liquid with a faint, pleasant odor, the synthetic industrial chemical is used as a solvent for extracting animal and vegetable oils and in the formulation of inks, coatings, and adhesives. In the laboratory, 1,4-Dioxane is useful as a cryoscopic solvent for molecular mass determinations and as a stable reaction medium for diverse reactions. 1,4-Dioxane is used primarily as a solvent in paints, varnishes, lacquers, cosmetics, deodorants, cleaning and detergent preparations, and in scintillating fluids. Literature searches also indicated the potential for use as a solvent in the processing of crude petroleum, petroleum refining, petrochemicals, pulp and paper, explosives, commercial printing, electroplating/polishing, pesticide and agricultural manufacture, dyes, fiber manufacture, pharmaceuticals, adhesives, semiconductors, electronic components, photographic equipment, magnetic recording media, polymers, plastics, rubber manufacture, and organic and inorganic chemical manufacture. 1,4-Dioxane often has been used with chlorinated solvents, particularly 1,1,1-trichloroethane (TCA), as a stabilizer and corrosion inhibitor.

When 1,4-Dioxane is used as a solvent stabilizer, the solvent itself is regulated as hazardous waste. When applied as an additive, 1,4-Dioxane is not used for its solvent properties and does not meet the regulatory definition of solvent. 1,4-Dioxane generally is listed with a group of pollutants in state and federal guidance for air pollution control and release reporting and in water pollutant control and National Pollutant Discharge Elimination System (NPDES) permitting.

1,4-Dioxane is highly flammable and potentially explosive if not stored properly. The chemical is a cyclic ether that is highly miscible in water and migrates rapidly in soil. 1,4-Dioxane contamination often can be found in association with releases of chlorinated solvents, particularly TCA. At some solvent release sites, 1,4-Dioxane has been found to migrate considerably farther in groundwater than solvents, such as TCA or its breakdown products (e.g., 1,1-dichloroethane), due to the compound's complete miscibility and the absence of conditions that promote its biodegradation (MADEP 2015). At other sites, however, the observed 1,4-Dioxane plumes were shorter than co-occurring chlorinated solvent plumes (Adamson et al. 2014).

EPA has listed the compound as a probable human carcinogen based on the results of animal studies, but little information is available on the long-term effects of 1,4-Dioxane on human health.

When in water the compound does not respond to air stripping or granular activated carbon treatment. Although 1,4-Dioxane has been considered resistant to naturally occurring biodegradation processes, there is evidence that intrinsic biodegradation can take place at 1,4-Dioxane sites under appropriate conditions (Adamson et al. 2015). Further discussion of intrinsic 1,4-Dioxane biodegradation can be found in Treatment Technologies. Chiang et al. (2016) reports that 1,4-Dioxane is not considered susceptible to chemical reduction (e.g., zero-valent iron), which also precludes anaerobic biodegradation, nor is oxidation with sodium permanganate an effective treatment; however,1,4-Dioxane in groundwater can be oxidized by activated sodium persulfate, ozone and peroxide, and modified Fenton's reagent. 1,4-Dioxane contaminated groundwater can be treated ex situ using modified Fenton's reagent, ultraviolet/peroxide, ozone/peroxide, or sodium persulfate (Mohr et al. 2010 and DiGuiseppi et al. 2016). Phytoremediation shows promise for 1,4-Dioxane removal at depths accessible to plant roots (DiGuiseppi et al. 2016 and Zhang et al. 2017).

For currently available test methods for 1,4-Dioxane see Site Characterization and Analytical Methods.

1,4-Dioxane and Other Solvent Stabilizers: White Paper
Mohr, T.K.G. Santa Clara Valley Water District, San Jose, CA. 55 pp, 2001.

This report summarizes information obtained on solvent stabilizers from an extensive literature review, and presents the nature and use of solvent stabilizers, how they behave in the subsurface, a description of laboratory analytical techniques, a summary of toxicological information for solvent stabilizer compounds, and a survey of the effectiveness and costs of available treatment technologies.

1,4-Dioxane White Paper
Water Resources Research Foundation, 6 pp, 2014

1,4-Dioxane industrial uses, health effects, occurrence, and treatment are briefly discussed.

Environmental Investigation and Remediation: 1,4-Dioxane and Other Solvent Stabilizers
Mohr, T., J. Stickney, and W. DiGuiseppi.
CRC Press, Boca Raton, FL. ISBN: 9781566706629, 550 pp, 2010

This book examines the uses, industrial history, environmental fate, laboratory analysis, toxicology, risk assessment, and treatment of 1,4-Dioxane in extensive detail. It also describes the controversy over interpretation of 1,4-Dioxane's toxicology and associated risk, as well as the corresponding disparity in state regulation of 1,4-Dioxane. Filled with case studies, equations, tables, figures, and citations, the book describes passive and active remediation strategies and treatment technologies for 1,4-Dioxane in groundwater.

Groundwater Information Sheet: 1,4 Dioxane
California State Water Resources Control Board, 6 pp, 2017

This brief groundwater information sheet provides general information (fate and transport, health effects, testing and remediation methods) related to groundwater sources used for public drinking water, not water served at the tap, and identifies where high levels of the compound are found in California.

Technical Fact Sheet: 1,4 Dioxane
U.S. EPA, Federal Facilities Restoration and Reuse Office.
EPA 505-F-17-011, 9 pp, 2017

This fact sheet provides a brief summary of the emerging contaminant 1,4-Dioxane, including physical and chemical properties; environmental and health impacts; existing federal and state guidelines; detection and treatment methods; and additional sources of information.

Technical Resources for Addressing Environmental Releases of 1,4 Dioxane
Interstate Technology and Regulatory Council (ITRC), 2020

The Interstate Technology and Regulatory Council (ITRC) has developed a series of fact sheets to summarize the latest science and emerging technologies for 1,4-Dioxane. The fact sheets are tailored to the needs of state regulatory program personnel who are tasked with making informed and timely decisions regarding 1,4-Dioxane sites. The content is also useful to consultants and parties responsible for the release of these contaminants, as well as public and tribal stakeholders.

Toxicological Profile for 1,4-Dioxane
Agency for Toxic Substances and Disease Registry (ATSDR), 295 pp, 2012

In addition to the toxicologic properties of 1,4-Dioxane, the profile contains chapters on chemical and physical information; production, import, use, and disposal; potential for human exposure (i.e., occurrence); and analytical methods.

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