Urethane in Alcoholic Beverages

by Food and Drug Administration (FDA)

The Food and Drug Administration is carefully evaluating studies to determine if there could be a long-term health risk to consumers from urethane in alcoholic beverages.

Urethane is a chemical substance that forms naturally during the fermentation process. It causes cancer in animals, but it is not known if it poses any significant health risk to humans. Based on data currently available, FDA does not believe that urethane levels in alcoholic beverages currently on the market are an immediate short-term health risk.

Until all scientific research is completed and evaluated, and regulations established, FDA is working with industry to reduce any potential risk to humans from urethane and is participating in tests to find out if the small amounts of urethane present in alcoholic beverages might be harmful.

Industry has voluntarily agreed to develop and use manufacturing techniques to reduce urethane's levels as much as possible. The Distilled Spirits Council of the United States (DISCUS), the American Association of Vintners, and the Wine Institute have told FDA they are studying how urethane forms during fermentation and are changing manufacturing processes to control its formation in alcoholic beverages.

FDA and the Bureau of Alcohol, Tobacco and Firearms (ATF) have done limited surveys of the urethane content in alcoholic beverages, and FDA has evaluated existing urethane toxicity data. In addition, at FDA's request, the National Toxicology Program, a federally funded research group, has done an initial study in animals to help FDA determine if urethane in alcohol poses a significant risk to humans.

Follow-up studies are not complete, and for now, according to the Cancer Assessment Committee of FDA's Center for Food Safety and Applied Nutrition, there is not yet enough information to assess the risk.

Urethane by Nature

Urethane formation is not a new phenomenon produced by high-tech processing. The chemical forms naturally in wine during yeast fermentation of fruit juice. Fermentation also produces urea from the yeast metabolism of arginine, an amino acid in grapes. Recent studies show that when urea reacts with ethyl alcohol after fermentation, ethyl carbamate, another name for urethane, results.

Alcoholic beverages other than wine present variations on this process, which complicates studies. Levels of urethane differ with each type of alcoholic beverage, explains Benjamin J. Canas, of FDA's division of food chemistry and technology. For example, heat seems to accelerate the production of urethane. Some sherries are baked to provide a rich taste, and bourbons are distilled at high temperatures. Both processes may raise urethane levels. Also, levels can differ significantly, even among different bottles of the same variety or brand, Canas says.

In 1985, work done by Health and Welfare Canada, FDA's Canadian counterpart, brought international attention to the issue of urethane in alcoholic beverages. Canadian authorities had detected the chemical in certain wines and distilled spirits, and had set levels for regulatory action.

FDA and ATF sampled the market and found that imported fruit brandies contained the highest levels of urethane — averaging a little less than 1,200 parts per billion (ppb). Sake followed with about 300 ppb, and then bourbon with levels averaging 150 ppb.

Grape table wines had urethane levels averaging 13 ppb, but dessert wines, such as sherries and liqueurs, averaged about 115 ppb.

Industry Efforts

The wine and distilled spirits industries have invested in basic research, plant modifications, and analytical testing to achieve the reductions in urethane levels they've made so far, says Gregory W. Diachenko, Ph.D., chief of FDA's food formulation branch.

The Wine Institute, for example, is encouraging several changes in grape growing and wine production that can lower urethane levels. For example, it is encouraging grape growers to minimize fertilization. Heavily fertilized vineyards tend to produce grapes that contain high levels of arginine, thus leading to higher urea and urethane levels.

The institute also recommends using a type of yeast, known by the French name prise de mousse, for the fermentation process. This yeast produces wine with lower levels of urea. And the institute is asking the industry to fortify (add alcohol to) dessert wines at a specific time during the fermentation process when the urea levels are the lowest. (Fortified wines contain more than 14 percent alcohol and have the most urethane of all wines.)

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.