Emerging Contaminants: 1,4-Dioxane

1,4-Dioxane is a semi-volatile, colorless liquid with a mild ethereal odor, also known as diethylene dioxide, dioxane, or p-dioxane. It is miscible with water, oils and most chlorinated solvents. It is also flammable and, during storage, may form explosive peroxides.

Sources of 1,4-Dioxane 

1,4-Dioxane is primarily used as a stabilizer in chlorinated solvents. At one time, approximately 90% of the 1,4-dioxane produced went into the production of 1,1,1-trichloroethane (TCA). This application has now been phased out due to TCA’s destructive effects on atmospheric ozone.

Industries or processes in which 1,4-Dioxane is used, or is associated, include:

  • Chlorinated solvents manufacturing (as a stabilizer)
  • Organic chemical manufacturing
  • Textile processing
  • Paper manufacturing
  • Varnish stripper and paint production
  • Pesticide production

Few manufacturers of 1,4-Dioxane exist globally as many previous uses of 1,4-Dioxane have been discontinued due to the potential carcinogenic effects of the chemical. 

When released into the air, 1,4-Dioxane degrades relatively quickly through reactions with photochemically-produced hydroxyl radicals. However, degradation in water and soil is slow. For this reason, 1,4-Dioxane is persistent in the environment, and will remain present in areas of groundwater contamination

The annual release in 2009 was approximately 130,000 lbs. Of this, 60% was released to air, 35% were surface water emissions, with the remaining being released to land. Due to the ubiquitous nature of 1,4-Dioxane, contamination can be found in many parts of the U.S.

A Probable Carcinogen

Until recently, 1,4-Dioxane was not considered a priority contaminant. However, in 2010 the United States Environmental Protection Agency’s (USEPA) Integrated Risk Information System (IRIS) updated its toxicological review of the contaminant to include a cancer assessment. IRIS designated 1,4-Dioxane as “likely to be carcinogenic to humans”. In addition, the IRIS system indicated that 1,4-dioxide concentrations of 0.35 ppb (ug/L) or higher in drinking water would result in 1 in 1,000,000 people developing cancer. In animal testing, 1,4-Dioxane increased the incidence of cancer in the liver, lungs, gall bladder, and on the skin.

Non-carcinogenic side effects of 1,4-Dioxane include liver and kidney toxicity. The primary routes of human exposure to 1,4-dioxane are inhalation, ingestion, and dermal contact.

The USEPA included 1,4-Dioxane on its third Unregulated Contaminant Monitoring Rule (UCMR3) for drinking water contaminants. Levels of 1,4-Dioxane will be monitored at 800 water treatment plants across the U.S. between 2013 and 2015 to determine if federal regulations are necessary.

Chemical Name 1,4 - Dioxane
Chemical FormulaC4H8O2
Molecular Weight88.12
Water SolubilityHighly Soluble
Density 1.033 g/mL
VolatilitySemi-volatilie
A TrojanUVPhox installation treating 1,4-dioxane in Stockton, California
Figure 1. TrojanUVPhox system treating 1,4-dioxane.

UV Light Key to Treatment Process

1,4-Dioxane’s low vapor pressure and high solubility render air stripping, carbon adsorption and reverse osmosis ineffective for its removal. However, UV-oxidation using UV light and hydrogen peroxide is effective at breaking down 1,4-Dioxane.

The irradiation of hydrogen peroxide by UV light generates hydroxyl radicals. These radicals effectively oxidize 1,4-Dioxane, breaking it down into its non-toxic molecular components.

Treating Multiple Contaminants With One UV System

As an added benefit to 1,4-Dioxane treatment, TrojanUV Advanced Oxidation systems also disinfect (inactivating pathogenic microorganisms including Cryptosporidium) and treat for other compounds including N-nitrosodimethylamine (NDMA), endocrine disruptor compounds, pesticides, volatile organic compounds (VOCs), and taste and odor causing compounds such as MIB and geosmin.

References: 

National Toxicology Program: 12th Report on Carcinogens, 2011; EPA Toxic Release Inventory, 2009; EPA Integrated Risk Information System (IRIS)