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Risk Policy Report on 1,4 Dioxane

[Editor's note: Read the OCA's recent 1,4 dioxane study results here]

A new EPA assessment showing significantly greater cancer risks from the solvent 1,4 dioxane -- a common contaminant at waste sites and in personal care products -- may give environmentalists greater leverage in their calls for manufacturers to remove the chemical from their products and for stricter cleanup requirements.

"A new assessment showing [dioxane] is 17 times more potent than they thought is a big concern because we are finding it in many children's products," a source with the Environmental Working Group (EWG) told Risk Policy Report. Among the products activists are targeting is a popular Dial soap, which they say contains among the highest levels of the chemical among the tested products.

EPA May 7 released a draft Integrated Risk Information System (IRIS) assessment of 1,4 dioxane that includes a new cancer slope factor that is 17 times more potent than the agency's 1990 IRIS assessment. The new assessment raises the oral cancer slope factor, a measure of a substance's cancer risks, from 0.011 milligrams per kilogram per day (mg/kg-day) to 0.19 mg/kg-day. It also includes for the first time a reference dose (RfD), the amount of the chemical EPA considers safe to consume orally on a daily basis, of 0.03 mg/kg-day. The draft indicates there was insufficient data to calculate a reference concentration (RfC), or the amount EPA considers safe to inhale on a daily basis. The document is available on

1,4 dioxane has long been a concern in drinking water and at Superfund sites. In 2007, the Agency for Toxic Substances & Disease Registry listed the chemical among the top contaminants at waste sites. Data on EPA's web site says the greatest risk stems from low-level inhalation by workers exposed to the chemical.

Nevertheless, some sources have been calling for EPA to more strictly regulate the chemical in water. During peer review of EPA's list of chemicals that it requires water treatment facilities to monitor, an official with the California Groundwater Resources Association (CGRA) urged EPA to add 1,4 dioxane to the list of substances subject to enforceable cleanup standards under the Safe Drinking Water Act since the chemical is increasingly found in groundwater and drinking water.

"1,4 dioxane is springing up at an increasing frequency," CGRA's Thomas Mohr told the Science Advisory Board last August, "it shows up because it's very persistent and mobile." Mohr noted that as many as 20 states are either considering or have instituted advisory levels for the contaminant. In the state of Colorado, which has adopted a legal standard, the state "recognized about 20 or more sites where this contaminant is threatening drinking water."

The solvent is being phased out of many previous industrial uses because of California's concerns about the chemical, an industry source says -- it has been listed as a carcinogen on the state's Proposition 65 list since 1988 -- but it remains in use in the production of many personal care products, according to activists. EWG, the Campaign for Safe Cosmetics and the Organic Consumers Association have sponsored testing of hundreds of shampoos, soaps, bubble baths, lotions and other personal care products for dioxane for the past three years, and publish the amounts of the chemical found in each product.

Following the results of testing released in March, the groups called for a ban of Dial soap products. Their testing of one Dial hand soap indicated it contained some 18 parts per million of dioxane -- among the highest tested. The chemical also shows up in nearly half of the personal care products that EWG includes in its "Skin Deep" database, which compares more than 42,000 personal care products with some 50 toxicity and regulatory databases, the EWG source says.

But the source says 1,4 dioxane is not listed among the products' ingredients because it is considered a contaminant, not an ingredient. Dioxane is a byproduct of a process called ethoxylation which softens the irritating effects the soaps otherwise would have, the source says.

Dioxane is not a well-known chemical like some plastic ingredients that activists have sought to ban, the source acknowledges. Still, the source says it is a perfect example of the kind of chemical that should be regulated under comprehensive changes to U.S. toxics laws. The source points to legislation recently introduced by Sen. Kirsten Gillibrand (D-NY) which would require extensive testing of personal care products.

Gillibrand's S. 925, requires the Commissioner of Food and Drugs to test within 180 days of the bill's enactment "a full range of cosmetics [and] personal care products" used by children seven years and younger that are "likely contaminated with impurities or contaminants" including 1,4 dioxane, acrylamide, ethylene oxide, dioxin, formaldehyde and lead, among others. -- Maria Hegstad