For many consumers, the prospect of eating produce zapped with ionizing radiation doesn't sound all that appetizing, conjuring up images of mushy fruits and wilted leaves -- not to mention fears over safety. Last month's ruling by the Food and Drug Administration that food manufacturers can now irradiate fresh spinach and iceberg lettuce to kill bacteria came with reassurances that the process wouldn't result in food any less appealing or healthful than non-irradiated varieties.
Research indicates that that may all be true. But critics say the new rule ignores the source of the problem -- sloppy agricultural practices -- and could give consumers a false sense of security.
For The Record
Los Angeles Times Friday, September 05, 2008 Home Edition Main News Part A Page 2 National Desk 1 inches; 66 words Type of Material: Correction
E. coli: An article in Monday's Health section about irradiation of spinach and lettuce said it takes hundreds of millions of E. coli bacteria to make someone sick. In fact, the number for E coli O157:H7 -- a strain associated with serious cases of food-borne illness -- is far lower than that. The number is estimated to be as few as 10 to several hundred cells.
For The Record
Los Angeles Times Monday, September 08, 2008 Home Edition Health Part F Page 6 Features Desk 1 inches; 67 words Type of Material: Correction
E. coli: A Sept. 1 Health section article about irradiation of spinach and lettuce said that it takes hundreds of millions of E. coli bacteria to make someone sick. In fact, the number for E. coli O157:H7 -- a strain associated with serious cases of food-borne illness -- is far lower than that. The number is estimated to be as few as 10 to several hundred cells.
One might imagine that washing would take care of most bacteria on a piece of fresh fruit or a vegetable -- including the forms of E. coli and salmonella implicated in recent food-borne disease outbreaks. But the microbes that spurred the Washington, D.C.-based Grocery Manufacturers Assn., an industry group, to request the current ruling are known as internalized bacteria -- so called because they've taken up inside the plant's tissues and can't just be washed off under the faucet.
Food irradiation, on the other hand, does penetrate deep. The process uses high-energy particles, usually in the form of gamma rays (generated by radioactive cobalt) or electron beams (similar to those in a television set). The particles break up water molecules in the plant, which then release free radicals that damage cell walls and DNA of any reproducing bacteria nearby.
Contrary to popular perception, the food doesn't retain radiation any more than, say, skin does after a day in the sun -- which is to say, not at all. It heats up a bit during treatment, then the radiation dissipates -- and no radioactive compounds enter the food.
When the radiation dose is kept low enough, the plant's own cells remain largely intact. When it's too high, however, the whole plant suffers. Irradiated food's reputation suffered a blow half a century ago, says Brendan Niemira, acting research leader with the U.S. Department of Agriculture's in Wyndmoor, Penn. Early experiments to develop an eternally shelf-stable head of lettuce resulted in leaves that were limp, colorless and bland.
Back then, scientists were dosing food with up to 10 grays of radiation. (A gray is a measure of how much energy is absorbed: It corresponds to one joule of energy per kilogram of matter.) The FDA's new rule allows food manufacturers to dose spinach and iceberg lettuce with up to 4 grays, enough to kill germs without withering plant material.
The agency already allows food makers to irradiate meat, poultry, spices and some types of shellfish. In fact, irradiation is widely used on the spices in processed foods, said Anuradha Prakash, professor of food science and nutrition at Chapman University in Orange. (Irradiated whole products, such as ground beef, must bear an internationally recognized symbol, known as the radura, or state that they've been treated with radiation.)
The recent decision to expand irradiation to lettuce and spinach was based in part on studies demonstrating irradiation's effectiveness at killing harmful microbes. For example, Niemira's studies, which focused on spinach and lettuce, showed that irradiation was up to four times as effective at ridding the greens of internalized E. coli when compared with washing with water or a chlorine solution. He also showed that irradiation is particularly effective at reducing the amount of E. coli stored up in iceberg lettuce.
But critics argue that effectiveness aside, irradiation has unwanted side effects -- including the creation of chemicals such as furans and 2-alkylcyclobutanones, which may be toxic in very high doses, and the destruction of vitamins and minerals. Furthermore, says Bill Freese, science policy analyst with the Washington, D.C.-based advocacy group Center for Food Safety, "food irradiation masks the unsanitary conditions of industrial agriculture."
Irradiating food can create chemical changes in food, but these are little different from the chemical changes yielded by processing, Prakash says. Compounds such as furans are also generated by cooking, she says. Ones unique to irradiated foods, such as 2-alkylcyclobutanones (which in some studies, but not others, have been shown to damage DNA) are generated at very low levels. Decades of animal feeding tests, Prakash adds, suggest that irradiated foods don't contain levels of chemicals that pose any risk to health.