By John Schwartz
Washington Post Staff Writer
Monday, December 8, 1997; Page A03

In the war on food poisoning, the federal government has gone nuclear.

The Food and Drug Administration last week approved irradiation to kill potentially deadly microbes in beef, lamb, or goat meat, as well as in edible byproducts such as organ meat.

The scientific community and public health organizations are in near-total agreement that it is safe to eat food that has been sterilized by radiation at the levels approved by the FDA. Many consumers, however, remain wary.

At the same time, consumers are increasingly worried about food poisoning, and for good reason: Food-borne infections cause millions of cases of human illness and an estimated 9,000 deaths annually in the United States. Meat safety has been of particular concern since an outbreak of food poisoning from fast-food hamburgers contaminated with E. coli bacteria killed four children and sickened hundreds of others in 1993. Earlier this year, E. coli contamination led to the recall of a record 25 million pounds of ground beef processed by Hudson Foods Inc.

The notion of using radiation to sterilize foods has been around for nearly 100 years, and use began in earnest about 40 years ago. These days half of all disposable medical devices go through the process, along with nipples for baby bottles, wine corks and those tiny foil-covered cups of half-and-half for your morning coffee. The first foods approved for irradiation were wheat and wheat flour in 1963; since then Uncle Sam has given the nod to use the approach on spices, pork, fruits and vegetables and poultry. The process sterilizes the food and lengthens shelf life.

The most common processes use gamma radiation, a high-frequency electromagnetic radiation that is generated when the nuclei of atoms break down. Most irradiation plants use cobalt ore that has picked up an extra neutron by being placed in a nuclear reactor. That extra subatomic particle bumps up the atomic weight -- the number of protons and neutrons -- from cobalt's usual, stable 59 to the unstable 60. This unstable radioisotope decays into nickel, shedding a beta particle (basically, an electron) and emitting a burst of gamma radiation.

It is this gamma radiation that goes through the meat, killing most (but not all) bacteria, such as E. coli 0157:H7 and salmonella. (It does not, however, kill viruses such as hepatitis in the doses approved by the FDA.) Although scientists are not certain of the precise mechanism by which gamma radiation kills bacteria, they do know that it strips electrons off atoms, disrupting the bonds between molecules, which could in turn disrupt the function of DNA and weaken cell walls.

Why then, doesn't the process leave food radioactive? George H. Pauli, an FDA expert on irradiation, explained that gamma rays are part of the electromagnetic spectrum, which also includes visible light and radio waves. Just as the furniture in a room doesn't continue to glow after you turn off the lights, materials that have been hit with gamma rays at the levels approved by the FDA -- 4.5 kiloGrays for fresh meat and 7 kiloGrays for frozen -- don't become radioactive. (A kiloGray is a measurement of energy absorbed by tissue.) The rays hit the meat and go through, and some of that energy is transferred into a slight amount of heat. The rays don't have enough energy to cause the kinds of changes in atomic nuclei that cause substances to emit radiation, Pauli said.

Some changes do occur in irradiated foods, however. Levels of nutrients such as vitamin E are reduced, but to a much lesser extent than the same losses from cooking. In addition, some "radiolytic" products have been identified -- chemicals in food that are created by the exposure to gamma rays. FDA officials noted that most of them are also found in cooked food, however -- not surprising, since irradiation, like cooking, is a transfer of energy into food. None of the byproducts has been shown to be dangerous.

"We've really looked carefully to see if there was anything toxic or anything harmful generated by using radiation at these doses," said Michael A. Friedman, the lead deputy FDA commissioner. "We were not able to find any noxious byproduct" at the doses tested. Since zapping meats too much tends to render them rancid, the food processors have strong incentive to stick to the approved amounts.

In a Federal Register filing that accompanied the approval, the FDA noted that it is "impossible to establish with complete certainty the absolute harmlessness of any chemical substance." Instead, the agency wrote, under its governing statutes its focus is "the reduction of uncertainty about the safety of an additive to the point where the agency can reasonably conclude that no harm will result from its use."

Even though virtually all public health groups have determined that irradiated foods are safe to eat, some consumer advocates raise questions about the expense of the process, the effectiveness of it in actually fighting contamination and potential problems of handling and transporting radioactive materials used in the most common processes.

The safety issues do not bother Grace Masefield, whose company, Isomedix, first petitioned the FDA three years ago to approve irradiation for meat. Masefield said that if meat processing plants want to build irradiation facilities on site, her company will be there to provide consulting and the federal government will be there to provide a regulatory structure. "It's just not going to be `anybody can build it and do what they want.' It's going to be very much guided," Masefield said.

But consumer advocate Carol Tucker Foreman cautions that irradiation too often is seen as a "fast, easy solution" to problems such as E. coli. "We certainly do not believe that irradiation provides a silver bullet that will make the problem go away," said Foreman, speaking for the Safe Food Coalition during recent congressional testimony. Unless food is sterilized in the final packaging that goes to consumers, the chance of recontamination is high, she said. "We are extremely concerned that irradiation not become a substitute for sanitation," Foreman said.

The technology is appropriate for some foods and not others. Mangoes take the treatment well, but "try to irradiate lettuce you'll probably have a wilted mess," said Pauli. Regulators at the Agriculture Department, which has authority over processing of meat and poultry, will have to work together to determine how to best apply the technology, Pauli said.

Foreman has also criticized industry efforts to shrink the label announcing that food has been irradiated. "If it is safe," she asked, "why hide it?"

IN IRRADIATION PLANTS, a radioactive isotope of cobalt (or in some cases, cesium) is stored in pencil-like stainless steel casings that are about 11/2 feet long and 3/8 inch in diameter. These casings are kept in a pool of water, which absorbs the gamma radiation, inside the heavily walled facility. The materials to be irradiated are brought in, either in batches arrayed around the pool or on conveyor belts that run by it. Machinery lifts the casings out of the water to irradiate the goods. Many systems rotate the containers to allow all-around exposure.

An alternative system fires a beam of electrons over the products, which could be safer for workers but sterilizes meat only to a depth of about three inches. This makes it effective for sterilizing hamburger patties on a conveyor belt but not for treatment of bulk meats.