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Eating Microwave Popcorn
May Expose You To Carcinogens


Preliminary FDA data suggest that eating microwave pop corn may expose people to chemicals that break down to produce PFOA, a suspected carcinogen.

New research shows that the grease-repelling fluorotelomer chemicals used to treat some microwave popcorn bags can migrate into the popcorn oil. The fluorotelomers are known to break down to produce PFOA, a suspected carcinogen that is commonly found in the blood.

Results of a study by the U.S. Food and Drug Administration (FDA) published in October reveal that compounds known to break down into the suspected carcinogen PFOA (perfluorooctanoic acid) may be served up to millions of unwitting consumers in bags of microwave popcorn. The family treat could account for more than 20% of the average PFOA levels now measured in the blood of the U.S. population.

Most Americans carry 4-5 parts per billion (ppb) of PFOA in their blood, according to the U.S. EPA's draft PFOA risk assessment, but its source has been unknown. Products used in the home are thought to play a role, including nonstick cookware such as Teflon pans, which are produced by a process that uses PFOA. But a growing number of studies, including this one, suggest that nonstick cookware is not a major source.

The FDA team investigated consumer products that contact food--nonstick pans, food wraps, and papers--as potential sources, says FDA chemist Timothy Begley, the study's lead author. Some of the papers used for packaging food are treated with grease-repelling fluorotelomer coatings. Microwave popcorn bags have the most of any food wrappers-- about 4000 milligrams per kilogram (mg/kg) in the coating or 25 mg per square decimeter of paper, the authors note.

Many of these coatings contain mixtures of long-chain chemicals that can be metabolized to PFOA, Begley and colleagues write in their Food Additives & Contaminants article.

The scientists found that a significant percentage of the fluorotelomers migrated from the bags to the popcorn oil, resulting in levels of 3-4 mg/kg. These concentrations are hundreds of times higher than the amount of PFOA that could migrate from nonstick cookware the first time it is heated above 175 °C. Because the surface area of a microwave popcorn bag is about 1000 square centimeters, a person consuming a bag's worth could take up to 110 micrograms of fluorotelomers, according to three toxicologists who performed these calculations on the condition of anonymity.

Toxicologists commonly convert such an exposure into a human dose by dividing by the average adult body weight, 65 kg. This means that the average dose of fluorotelomers from each bag of popcorn is 1.7 micrograms per kilogram. Children who ate a whole bag would get a higher dose.

Scientists don't currently know how readily humans can metabolize fluorotelomers to PFOA, says University of Alberta (Canada) biochemist Jonathan Martin. But in a recent article in Chemico-Biological Interactions, he reports that rat liver cells can directly convert 1.4% of fluorotelomer alcohol to PFOA. Another 7% of the fluorotelomer alcohol is metabolized to intermediate acids that are also expected to eventually degrade to PFOA. So a conservative estimate for the conversion from fluorotelomers to PFOA is 1%. This means that a person eating a whole bag of popcorn could take up 0.017 ppb of PFOA.

Given that the average PFOA content of human blood is about 4 ppb, a person would have to eat about 300 bags of microwave popcorn over 5-10 years (about a bag a week) if all the PFOA in their blood came from the snack. Toxicologists say that 5-10 years is an appropriate timescale for such a calculation because PFOA is reported to have a long half-life in humans, about 4 years. Although most people probably do not eat a bag a week, Americans do wolf down 39 million pounds, or about 156 million bags every year, according to the Snack Manufacturers Association. Consumption of just 10 bags of microwave popcorn a year could contribute about 20% of the average blood PFOA levels, say the scientists interviewed anonymously for this article.

"This dose is certainly not insignificant", Martin says. "Scientists should be, and are, considering polyfluorinated precursors [such as the fluorotelomers] as a potential human exposure pathway to perfluorinated acids, including PFOA", he adds.

Microwave popcorn bags probably represent the worst-case scenario for getting PFOA precursors into foods, Begley notes. This is because the amount of fluorotelomers in the coatings is high and because popcorn bags get very hot-they heat up to more than 200 °C in just a minute or two. These temperatures significantly increase the potential for migration of the packaging components to foods, he says.

Fluorotelomer coatings are not used in all microwave snack-food packaging. For example, microwavable stuffed sandwiches like Hot Pockets and microwave pizza do not use paper coated with fluorotelomers, according to Begley, who says that he's still conducting research on other papers and coatings.


Reference Source 125
November 24, 2005


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