We've come a long way since making popcorn meant shaking a pan of oil and kernels over high heat on the stove. Now, in less time that it takes to get through a commercial, we can pop a package in the microwave and get popcorn ready to serve in its own container. Our breakfast muffin heats up the

Heating and eating popcorn or breakfast in the wrappers that come from the grocery is a great convenience, and in this era of two-career families, convenience foods are in great demand. But is some of the wrap getting cooked into our food?

And what about packaged food -- like breed and cheese -- that's not heated? The wrap is pressed directly against the food, often for a long time. Sometimes, especially with cheese, we can faintly taste or smell the plastic wrap on the end pieces. Does that mean that we're eating more than cheese?

Food packaging is big business. A consultant for the Institute of Packaging Professionals says that 55 percent of all packaging made in the United States is for food. And the market is growing, especially for microwavable packaging.

Manufacturers are usually vigilant about the materials that go into their food packages. It's not good business if their packaging material makes someone sick -- and they know that the Food and Drug Administration (FDA) is watching, too.

FDA monitors packaging that comes in contact with food, whether it is used for transport from the food processor to the grocery, or from the grocery to the home -- or while it is being stored in the pantry or cooked in the microwave.

Manufacturers are required by law to onbtain approval from FDA for all the materials used in food packages before they can be marketed. Components that have been shown to cause cancer in humans or animals cannot be used.

Packaging components that already are on FDA's "generally recognized as safe" (GRAS) list for use in food or in food packages do not need a separate regulation.

The GRAS list was established with the 1958 Food Additives Amendment to the Federal Food, Drug, and Cosmetic Act. The only other components of packaging that do not require a regulation are those that have a "prior sanction" -- that is, those that were determined safe for use before 1958.

Bread Bags

Sometimes people use food packages for purposes other than FDA-regulated uses. For example, an article in the June 1991 American Journal of Public Health on research by the University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, reports that some people are turning bread bag inside out and reusing them to store food or pack lunches. Because the lead-containing ink used on the outside of some bread bags touches the food, the food can become contaminated with the lead. (Right side out, the lead-based ink printing on the bread wrapper does not come in contact with the bread.) Based on the study's findings, the scientists said that a weak acid, such as vinegar, in contact with the label printing could, estimating conservatively, extract about 5 per cent of the lead from the ink in as little as 10 minutes.

Most likely, no one would store vinegar in a plastic bag. But, for perspective, the authors of the study observed that a 100-square centimeter surface (about the surface area of a peeled orange, which is slightly less acidic than vinegar), in contact with the label printing, could leach about 100 micrograms of lead within 10 minutes. When eaten by an adult on a daily basis, 100 micrograms of lead converts to approximately 4 micrograms of lead per deciliter of blood.

FDA scientists have found that for adults, toxicity is associated with blood lead levels as low as 30 micrograms per deciliter. In fetuses, infants and children, toxic effects can be observed at blood lead levels of 10 micrograms per deciliter. Because of the toxic effect on the fetus, this level is also of concern for pregnant women.

Plastics

Now, about that end piece of cheese that tested a bit like the plastic it was wrapped in: The FDA refulation that deals with indirect additives says that if a regulated food-packaging material were found in an appropriate test to impart an odor or taste to a specific food product, the food is adulterated and therefore subject to regulatory action. Sometimes when cheese is not refrigerated for a short while (such as during the trip home from the grocery), the end pieces taste a little like plastic, even though it is safe to eat. Off-odor and taste is a problem for food processors and they try not to let off-taste happen.

Flavor trading also works in reverse. For example, that plastic jug you use to mix your orange in the morning still smells like juice even after you've scrubbed it with soap and hot water. That problem is known in the industry as "flavor scalping." Pladtic containers sometimes absorb flavors from citrus and other foods, lessening the flavor in the juice.

Migration of package components is rarely a problem eith containers that hold dry food, such as cereal. But when a food is wet -- and especially if it contains alcohol, acid, or fat -- chemicals from the packaging material could migrate into the food.

Microwave Packages

Regulations approving the safety of packaging materials heated with food were written before the advent of microwave packaging. These regulations did not anticipate the development of microwave packaging components, called heat susceptors, that act like a frying pan when you crisp a waffle, brown the bottom of a pizza, and pop popcorn, for instance.

Heat susceptors layers in a microwave package reach temperatures of 400 to 500 degrees Fahrenheit, a much higher temperature than was envisioned when the regulations were written. Heat susceptor packages are multilayered, with food containing the hot layer, usually a polyethylene terephthalate (PET) film with a thin layer is bound to the aluminum on the back. The heat susceptor layer is bound to the outer paper or papperboard by an adhesive.

FDA's laboratory studies have shown that a high temperatures, components of the PET film migrate at levels far in excess of those that the agency anticipated when it initially regulated the PET film as an indirect additive. In addition, FDA studies show that at these high temperatures, the PET food-contact layer cracks, facilitating the migration of the adhesive components of the package, as well as their degraded products, directly into food. (Adhesives were originally approved for use in packaging where a functional barrier would be between it and the food, resulting in minimal migration.)

Another concern is that high temperatures achieved by heat susceptors may cause the paper parts of the package to burn or char and partially decompose. These breakdown products could migrate into the food.

The aluminum component of the heat susceptor film is on the GRAS list, and FDA does not consider it a food additive problem. But because of the migration problem of the other components at high temperatures, FDA has requested additional data from manufacturers in order to reevaluate the regulations.

Based on the data submitted by industry and on FDA's oen data, several hundred components could migrate out of heat susceptor packages at extremely low levels at temperatures ranging from 400 to 500 degrees Fahrenheit.

One migrant chemical that has warranted special concern is benzene, which is known to cause cancer in humans. A 1988 FDA] study of 11 heat susceptor packages purchased from supermarkets showed that there were detectable low levels of benzene in eight of them. Extracted from FDA Journal (11-91).