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1,4-Dioxane—a New Contaminant of Concern

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1,4-dioxane has been a contaminant of concern for hazardous waste sites for a number of years due to its use as a solvent stabilizer. USEPA has prepared a summary web page on 1,4-dioxane, with critical information summarized here: 

“1,4-Dioxane is used as a solvent.  Acute (short-term) inhalation exposure to high levels of 1,4-dioxane has caused vertigo, drowsiness, headache, anorexia and irritation of the eyes, nose, throat, and lungs in humans.  It may also irritate the skin.  Damage to the liver and kidneys has been observed in rats chronically (long-term) exposed in their drinking water.  In three epidemiologic studies on workers exposed to 1,4-dioxane, the observed number of cancer cases did not differ from the expected cancer deaths.  Tumors have been observed in orally exposed animals.  EPA has classified 1,4-dioxane as a Group B2, probable human carcinogen.”

Tom Mohr from the Santa Clara Valley Water District has published a major review of 1,4-dioxane chemistry and occurrence.

More than a dozen states have set limits for 1,4-dioxane in ground water. Some states, such as California, have recommended monitoring for 1,4-dioxane in the CA recycled water regulations.  The one in one million (10-6) risk level for 1,4-dioxane is 0.35 ug/L.  Current analytical methods (USEPA 522 for example) are capable of precise and accurate measurements as low as 0.07 ug/L.

1,4-dioxane is not only used as an industrial solvent stabilizer, but is found in a variety of other consumer and industrial products, from cosmetics to inks.  


In 2013, when monitoring began under the USEPA Unregulated Contaminant Monitoring Rule 1,4-dioxane became a major issue for drinking water.

USEPA method 522 only requires the use of a 100 ml sample to achieve the 0.07 ug/L UCMR3 reporting limit. Eurofins Eaton Analytical was one of the first labs in the country to be approved by USEPA for 1,4-dioxane analysis under the UCMR3 program and has analyzed more than 5,000 samples for 1,4-dioxane in more than 500 public water supplies from across the country as part of the UCMR3 program. As testing is completed, results are made publicly available via the USEPA website.  As of April 2014, nearly 20% of public water supplies have been found to contain 1,4-dioxane, with levels as high as 9 ug/L for many utilities drawing water from the Cape Fear River in North Carolina. The widespread occurrence of 1,4-dioxane will likely lead to the future regulation of 1,4-dioxane in drinking water. With that in mind it is important for utilities to not only assess their occurrence data for 1,4-dioxane, but also to consider appropriate public communication strategies for 1,4-dioxane. 

The map below shows the occurrence patterns by source water type for 1,4-dioxane in public data available so far.