Plastic Packaging Contaminating Our Foods

Some Unanticipated Interactions
By Beatrice Trum Hunter
Republished with permission from Author
Taken from the Dec. 1993 issue of Consumers' Research Magazine

More than a decade ago, it was discovered that an ordinary Styrofoam cup could disintegrate when it held hot tea and lemon. Discoveries of such unanticipated interactions still occur from time to time.

For many years polystyrene egg containers have largely replaced paper mache. However, their safety has only recently been investigated, in 1991. The Louisiana Agricultural Experiment Station reported that volatile styrene monomers were detected in shell eggs stored in polystyrene containers for two weeks in the supermarket.  Egg dishes cooked with these contaminated eggs contained seven times more ethylbenzene and styrene than those prepared from fresh farm eggs that had not been packaged in polystyrene. It is suspected that the volatile compounds can migrate through the porous shells into the edible portions of the eggs.

Benzene from multilayer, oxygen-barrier, laminated bags has been found to migrate into meat, poultry, cheeses, and other packaged foods. This problem surfaced in September 1990 when an off odor was noticed in a roast beef shipment. Investigation showed the meat contained benzene from the packaging, ranging from less than 5 parts per billion(ppb) to 17.8 ppb in raw meat. The benzene volatilized when the meat was heated.

Increasingly, plastic food wraps and containers have gained in popularity for microwaving foods. This practice can release components from the plastics, including base monomers, plasticizers, colorants, and stabilizers,especially when high heat is used. Many plastics contain plasticizers, used to increase the wrap's flexibility. Some plasticizers have been found to migrate from the plastic into the food. One is DEHA [di(ethylhexyl) adepate], commonly used as a plasticizer in polyvinyl chloride (PVC) film wrap, which is popular for covering stored and microwaved food. DEHA is a suspected carcinogen.

In a 1987 study of home use of PVC film wrap, the DEHA migration level was found to increase in proportion to the time that the food was in contact with the PVC wrap and with the rise in cooking temperature. The highest migration levels were found when the plastic film was in direct contact with food with a high fat content on it's surface. The highest migration levels were found with microwaved meats (such as pork, spareribs, and roast chicken) and bakery products(such as cake, scones, and biscuits made with peanuts). Somewhat lower levels were found in fruits and vegetables, except avocado with its high fat content. Migration levels were low when there was little or no direct contact between the food and the wrap.

In the same study, use of PVC film with foods in retail stores was examined. Results were similar. The amount of DEHA migration into foods depended on how long the film was in contact with fatty surfaces of the food. The highest amount were found in cheeses, baked goods, and sandwiches; lower amounts in cooked meat and poultry; and the lowest in fruits and vegetables.

Polyethylene, a popular plastic film used for food freezer bags and wraps, does not contain plasticizers, and is considered to be generally safe for microwaving foods. However, if printing has been applied to the surface, the primer applied to the plastic prior to printing, as well as the applied inks, may subject the heated plastic to conditions distinctly different from those for which they had been tested and approved. Only clear polyethylene is suitable for microwaving food.

Formed plastic containers, used for carry-out foods, should not be reused for microwaving. Such containers, if heated, may be subjected to conditions other than those for which they had been safety tested.

Some plastic packaging material now in use for microwaving have not been approved for use at high heat. The most severe conditions for such packaging recognized by protocols of the Food and Drug Administration (FDA) were under conditions that previously had prevailed: from 212 F to 275 F. Recognizing the changes that have occurred, FDA scientists are working with members of the packaging industry to study new testing procedures, and to learn whether packaging materials can be modified to assure food safety when used for cooking at high heat.

Of concern, too, is "active packaging." Thin layers or strips of metallic heat susceptors are placed in plastic food packaging intended for microwaving. The susceptors focus microwave radiation to produce extremely hot surfaces (400F to 500F) within the package. This high heat permits food to be browned, crisped, or popped - features usually lacking in microwave cooking. At such high heat, substances such as polymers and their breakdown products, as well as adhesives and their components and other substances present in the plastic, can migrate into the food.. Originally, susceptor strips were approved by the FDA for a different purpose and were tested at far lower temperatures.

Polyethylene terephthalate (PET) is a popular plastic film wrap. It has long been assumed that PET film provides a functional barrier to adhesive components. It was demonstrated recently that the film allowed the migration of adhesive components into foods when oil or foods were cooked in contact with it. A study by the FDA's Division of Food Chemistry and Technology showed that the susceptor board components that migrated in the largest quantities were the plasticizers rather than the polymer components, even though the polymer components were in direct contact with the oil or food, whereas the plasticizers were in the adhesive layer of the susceptor boards. Approximately 50% more plasticizers migrated than did the polymer components.

For many years, a purple dye (FD&C Violet No.1) had been used to stamp inspected meat. The dye was suspected as a carcinogen. There was no assurance that the portion of the meat with the dye would be cut away before being consumed. In 1973, the FDA banned the dye as a meat marker.

Nitrosamines (carcinogenic compounds) were discovered in rubber nipples used to cap baby bottles. The rubber was reformulated to eliminate nitrosame formation. More recently, nitrosamines were discovered in hams that had rubber netting to encase them after boning and curing. The rubber was reformulated to eliminate this problem.

With rapidly changing packaging practices and many innovative techniques, manufacturers and regulators need to be vigilant in order to prevent unanticipated and undesirable interactions with foods.

The author, Beatrice Trum Hunter, MA, has written more than 30 books on food and environmental issues, frequently before widespread public awareness. She was food editor of Consumer's Research Magazine for more than two decades. She is an honorary member of The Price Pottenger Nutrition Foundation, as well as an honorary fellow of The International Academy of Preventative Medicine and an honorary member of The American Academy of Environmental Medicine. She has been the recipient of many awards, including The Jonathan Forman Award of The Society for Clinical Ecology, The New Hampshire Society for Preventative Dentistry, and The Donnon Pepper Humanitarian Award. She can be reached at 243 Falls Road, Deering, N.H. 03244