People can come into contact with dioxane through the use of cosmetics, shampoos, detergents and other consumer products with dioxane in them. Where solvents -- particularly TCA -- have polluted a groundwater aquifer or a surface water supply, consumers can be exposed to dioxane through the water they consume or through bathing and showering. Dioxane is transported in groundwater from a source of contamination more quickly than other solvents, so it may be present when other solvents are not.

The U.S. Environmental Protection Agency currently identifies dioxane as “likely to be carcinogenic to humans.” This finding is based primarily on toxicology studies conducted using rodents. EPA’s most recent analysis, completed in 2010, concluded that at a concentration of 0.35 parts per billion (ppb) over a lifetime exposure dioxane may lead to negative health effects.

As part of its recent Third Unregulated Contaminant Monitoring Rule testing, EPA is examining how prevalent dioxane is in U.S. drinking water supplies and at what level it occurs. Under the recent round of UCMR3 testing, many water systems nationwide tested for dioxane.

Contact your public water system to learn more about dioxane testing and results. If your water system observes dioxane in its testing, it will publish the results in its next annual consumer confidence report, which is publicly available. The report is often available on the internet, but you can also contact your water provider to request a copy. You can usually find contact information for your public water system on your water bill.

The federal drinking water standard for dioxane has not been established. EPA maintains an active program called the Contaminant Candidate List to identify contaminants in public drinking water that warrant detailed study. The third Contaminant Candidate List, CCL3, finalized on Sept. 22, 2009, includes 1,4-dioxane.

If there is scientifically compelling evidence that shows a large number of U.S. drinking water systems have high amounts of dioxane, it’s possible that they may decide to regulate dioxane in the future. Before regulating a contaminant, EPA considers projected adverse health effects from the contaminant, the extent of occurrence of the contaminant in drinking water, and whether regulation of the contaminant would present a meaningful opportunity for reducing risks to health.

If you get your drinking water from a private well, you should have your water tested by a certified laboratory at least once a year. You can find information on how to sample for dioxane and where to send samples for analysis by contacting your state water laboratory certification officer. Contact information for your state can be found on EPA’s drinking water lab certification page. Additional information about well water testing from EPA is available on their private drinking water well FAQ page

If you are concerned about dioxane in your drinking water, you may consider purchasing a home treatment device. However, in order to make a well-informed and cost-effective decision, consider:

• Checking with your water system or consumer confidence report to learn about the amount of dioxane in your water.
• Identifying a device that has been independently certified to remove dioxane.

NSF International, the Water Quality Association, Underwriters Laboratories and CSA International all certify home treatment products for removal of contaminants. The relevant dioxane removal standard is NSF/ANSI Standard 53. If you choose to use a home treatment device, it is very important to follow the manufacturer's operation and maintenance instructions carefully in order to make sure the device works properly.

Bottled water quality can vary. Bottled water in the United States is regulated by the U.S. Food and Drug Administration and is required to meet standards equal to the EPA’s tap water standards. There are also individual state standards. However, in most cases, you must contact the bottled water manufacturer for information about dioxane levels.