Irradiation involves subjecting certain foods (primarily spices, some fruits, and a limited amount of meats) to intense doses of ionizing radiation in the form of gamma rays, X-rays, or electron beams before sending them to market. Considered a food-safety intervention since 1963, when it was approved to control insects in wheat and flour, irradiation kills or deactivates harmful bacteria, including E. coli O157:H7, Salmonella, Campylobacter, Listeria, Clostridium, and Vibrio, thus reducing the threat of food-borne illnesses. According to the Centers for Disease Control and Prevention, these bugs cause approximately 3,000 deaths and 128,000 hospitalizations of Americans each year. Heat obviously does the same sort of thing, which is why milk, for instance, is pasteurized. But many pathogens are more difficult to kill than the ones pasteurization was designed for, and higher temperatures would affect flavor and texture adversely.
Irradiated foods must be stored, handled, and cooked in the same way as nonirradiated foods, but they have a longer shelf life because the process destroys molds and bacteria that cause spoilage and also slows down ripening or sprouting in plants. The Food and Agriculture Organization of the United Nations has estimated that about 25 percent of all worldwide food production is lost after harvesting to insects, bacteria, and spoilage.
The irradiation of food has been approved in 37 countries for more than 40 products. The largest marketers of irradiated food are Belgium, France, and the Netherlands, but overall, irradiated foods make up a small portion of the food supply. According to Food Safety News, in the United States about one-third of imported spices formerly fumigated with chemicals are irradiated; that amount could increase after the October 2013 release of the FDA’s draft risk assessment on the levels of pathogens and other unsavory contaminants found in 12 percent of spices imported to the U.S. Anyone who has traveled to India, for instance, or the Middle East, and seen the age-old ways in which spices are harvested, dried, and stored will not be surprised by this news. My gut reaction was “only 12 percent?”
Some imported fruits are irradiated as well to kill or sterilize any “hitchhiker” live pests, such as the mango seed weevil and certain fruit fly species, that may be problematic, if not potentially devastating, for American agriculture. The USDA’s Animal and Plant Health Inspection Service has approved the use of irradiation as a quarantine treatment for mangoes from India; lychees, longans, rambutans, pineapples, mangoes, and mangosteens from Thailand; dragon fruit from Vietnam; and guavas from Mexico. In the U.S., Hawaii, a pioneer in the technology, exports irradiated sweet potatoes, papayas and other tropical fruits, and fresh herbs such as curry leaf and basil to the mainland.
So how does irradiation affect the “sensory quality”—that’s flavor and texture to you and me—of tropical fruits? Those that have been given a post-harvest hot-vapor treatment, after all, are dispiriting, with a cooked flavor and texture, and I presumed the same would be true for irradiated specimens. “It depends entirely on the type of fruit,” explained David Karp, a renowned fruit authority who also keeps a sharp eye on the California farmers market scene. “As far as mangoes go, certain cultivars are highly susceptible, and others aren’t. In some, the flavor improves.” Karp is a strong believer in eating seasonal foods that are as fresh as possible, but he’s no absolutist. “Irradiation provides access to both growers, who wish to export, and consumers, who wish to eat those foods,” he said.
A Band-Aid Solution to an Intractable Problem?
One objection to making food irradiation more common in the United States—especially in light of USDA shutdowns like the one at a Central Valley slaughterhouse earlier this week—is the perfectly reasonable concern that the food industry will rely on irradiation as a last-ditch measure to protect consumers from illness instead of preventing contamination with stringent husbandry and sanitation protocols in the first place. While irradiation works beautifully on bacteria, it doesn’t affect viruses and prions, the infectious agents believed to cause bovine spongiform encephalopathy (aka BSE, or mad cow disease). NYU public health authority (and queen of the sound bite) Marion Nestle calls it a “late stage techno-fix.”
E. coli 0157:H7 is a case in point: Outbreaks have been caused by contaminated foods such as bean sprouts, spinach, and other leafy greens, cantaloupe, and most famously, ground beef. How does this happen? A 2011 report from the American Academy of Microbiology cuts to the chase: “It all starts with poop,” it reads. “Because E. coli lives in the gut, transmission of E. coli from one organism to another is predominantly from feces to mouth. The source of E. coli in almost all food and water contamination events can be traced back to exposure to fecal matter at some point in the food chain; whether it is on the farm, at the processing plant, in transportation, during retail, at the restaurant, or even during preparation in our homes.”
Ground beef is especially worrisome: The act of grinding distributes surface bacteria throughout the product, which is why it’s important to cook it thoroughly. I think I can speak for us all when I say I don’t want to eat fecal matter in my ground beef, irradiated or not. (Still, do I forgo a great burger every so often? Not no, but hell no. That said, I grind the meat myself.)
Interest is also growing in the possible irradiation of fresh leafy greens and other produce. Although organic foods cannot be irradiated, the Organic Center, a good clearinghouse for the science behind organic food and farming, published a fascinating Critical Issue Report on irradiation for fresh produce in 2007.
Speaking of Band-Aids, among the many other uses of irradiation is the sterilization, for more than 50 years, of health care products, from those adhesive strips to ear swabs, syringes, and surgical implants.
Health Effects of Irradiation
Another concern among consumers is about the relative safety or healthfulness of irradiated food. Below are some commonly asked questions, along with answers drawn from the scientific community, including the World Health Organization, which published this detailed technical report in 1999.
Does irradiation turn food radioactive?
No. To quote Extoxnet, a collaboration among extension toxicologists from the University of California, Davis; Cornell University; Oregon State University; University of Idaho; and Michigan State University, “the food itself never contacts a radioactive substance, and the ionizing radiation used is not strong enough to disintegrate the nucleus of even one atom of a food molecule.” The folks at the University of Wisconsin Food Irradiation Education Group have a great analogy: “Just as the airport scanner doesn’t make your suitcase radioactive, this process is not capable of inducing radioactivity in any material, including food.”
Does irradiation cause chemical changes in food?
Yes. “That is how it kills bacteria,” writes nuclear chemist and science writer Robert L. Wolke in What Einstein Told His Cook. “But while the changes in the bacteria’s DNA are lethal to them, the amount of chemical change in the food itself is minuscule at the radiation intensities used.... Cooking causes chemical changes too, of course.”
Does irradiation kill nutrients as well as harmful microorganisms?
Yes. The same is also true of cooking and food preservation methods such as pasteurization, which took many years to gain public acceptance, and canning. The nutrients lost will vary, depending on the food source and the vitamins in question. According to the Organic Center report, “irradiation of citrus fruits and juices has been shown to oxidize a portion of the ascorbic acid (Vitamin C); but...since the oxidized and the nonoxidized forms of the molecule are both biologically active, the nutritional impacts of this effect are likely to be minimal.... Three varieties of irradiated lettuce contained higher levels of antioxidants and phenols (desirable nutrients) than controls; i.e., irradiation in this case improved the nutritional quality of the food.” If you eat a balanced diet, and one that’s not limited solely to irradiated foods, then I wouldn’t worry.
When food is irradiated, doesn’t it form dangerous or carcinogenic compounds?
According to a 2011 paper published in the European Food Safety Authority Journal, “the main reported radiolytic products [new compounds] are certain hydrocarbons and 2-alkylcyclobutanones [2-ACBs] produced from the major fatty acids in food, and some cholesterol oxides and furans. Most of these substances are also formed in food that has been subjected to other processing treatments and are thus not exclusively formed by irradiation. Furthermore, the quantities in which they occur in irradiated food are not significantly higher than those being formed in heat treatments.”
The Organic Center report mentions a few radiolytic products specifically, including formaldehyde and furan, which is formed in irradiated high-carbohydrate foods, and, as it turns out, in a variety of cooked foods, including baked bread and roasted coffee: “Furan causes cancer in rodents fed high doses, and its presence in foods, even at low levels, automatically triggers regulatory concerns. Awareness that furan was produced in irradiated foods led FDA and industry scientists to test similar nonirradiated foods for furan; they found that cooking also produces furan in many foods, generally at higher levels than are found in irradiated foods.”
How can you tell what foods are irradiated?
The FDA requires that both the international Radura logo and the words “treated with irradiation” or “treated by irradiation” appear on packaged foods, bulk containers of unpackaged foods, placards at the point of purchase (for fresh produce), and invoices for irradiated ingredients and products sold to food processors. Foods that contain irradiated ingredients (such as the spices in sausages or packaged foods) do not have to be labeled, and restaurants don’t have to disclose the use of irradiated ingredients.
What about radioactive waste disposal?
We are all mindful of the enormous quantity of radioactive waste generated during the reprocessing of nuclear reactor fuels, but as Wolke explains in What Einstein Told His Cook, “a food irradiator...is as different from a nuclear reactor as a flashlight battery is from an electric generating plant. Radioactive materials are indeed being used, but there is no waste build-up from their use.”