In the wake of Europe’s recent E. coli outbreak, in which sprouts contaminated with a particularly vicious strain killed 36 people and sickened thousands, food safety officials are asking once again what more can be done to curb the spread of food-borne illnesses.
Food-borne infections in the U.S. have declined 20% over the last 10 years, thanks to tighter regulations and steps taken by the food and agricultural industries, according to the Centers for Disease Control and Prevention. But they still cause more than 48 million cases of illness and about 3,000 deaths each year.
Some experts say part of the solution lies with food irradiation — an effective, underused method of prevention that’s been around for more than 100 years.
Food irradiation involves treating items with low-dose X-rays, electron beams or gamma rays. The high-energy particles in the rays and beams kill disease-causing pathogens such as E. coli and salmonella by damaging their genetic material. The particles also break up water molecules in the food, releasing free radicals that can kill bacteria and parasites.
No radioactive materials end up in the food itself, even though in the case of gamma rays the source is radioactive cobalt, said food irradiation expert Christine Bruhn, director of the Center for Consumer Research at UC Davis. Electron-beam and X-ray irradiation involve no radioactive elements, Bruhn added.
But widespread fears about nuclear radiation in the 1950s led Congress to require the Food and Drug Administration to regulate irradiation as a food additive instead of a treatment process. As a result, all irradiated food has to bear a label. (The exceptions are irradiated food sold in restaurants, and cases when the whole food item hasn’t been irradiated but ingredients like spices have been.)
In the 1960s, the FDA approved irradiation to prevent mold growth in wheat flour and sprouting in potatoes; in the 1980s, the agency added pork and produce to the list to kill the food-borne pathogen trichinosis (in pork) and insects (on produce). Irradiation is also approved to kill pathogens in raw oysters, red meat, poultry, shell eggs, sprouts, spinach and iceberg lettuce. (Food consumed by astronauts on long trips to space is also often irradiated to extend shelf life.)
But because manufacturers have been reluctant to proclaim the treatment to consumers, irradiation hasn’t been widely used.
The top use of irradiation in the U.S. is to treat spices used by the food industry; 175 million pounds of spices — a third of the spices used in commercial production — are irradiated, said Ronald Eustice, national director of the Minnesota Beef Council and a consultant to the Food Irradiation Processors Alliance.
A smaller fraction of the meat supply is irradiated: about 18 million pounds of meat and poultry, or less than half of 1% of the total. Among produce, irradiation is used mostly to kill insects on imported tropical fruits, such as mangoes, guavas and papayas. Each year, 35 million pounds of tropical produce are irradiated.
Because irradiation penetrates food, the process can kill pathogens that have been taken up into seeds or plants. That makes it useful for eliminating germs that can’t be addressed by washing produce in the kitchen sink, said food irradiation researcher Rosana Moreira, a professor in the department of biological and agricultural engineering at Texas A&M University in College Station.
Not all foods can be irradiated, Moreira added. Some high-fat foods, such as milk and cheese, can acquire off-flavors after the treatment.
And even though meats and produce can be irradiated, the dose must be calibrated just right so that the rays penetrate the entire food. With irregularly shaped foods, such as a mango or a head of broccoli, that can be a challenge. If the dose is too low, pathogens may remain in the food. If the dose is too high, it can cause pitting, bruise-like marks, damage to a fruit’s skin, off flavors and reduced shelf life.
Despite these technical challenges, food irradiation has great potential to prevent food-borne illnesses, experts said. If used on fresh produce, spices and grains, it could cut down significantly on pathogens such as E. coli, salmonella and shigella, Moreira said. On ready-to-eat meats, such as frozen hamburgers, hot dogs and deli meats, it can virtually eliminate any contaminating bacteria, Bruhn added. (Because of their regular shapes, such products are easy to irradiate evenly and thoroughly.)
Few formal estimates exist of how many food-borne illnesses would be prevented with more widespread use of food irradiation. However, a 2001 analysis in the journal Emerging Infectious Diseases calculated that irradiating half of the meat and poultry consumed in the U.S. would prevent more than 880,000 cases of illness, 8,500 hospitalizations and 352 deaths a year. Similar estimates on produce have not been done. The CDC says that irradiation may be able to eliminate pathogens from sprouts (although treating sprout seeds with a high enough dose to kill internal germs could destroy the seeds’ ability to germinate).
“If those sprouts in Germany had been irradiated, this situation in Europe could have been prevented,” Eustice said.
Worldwide, 40 countries have either approved or currently use irradiation for more than 50 food products, including spices, teas, onions, potatoes, fruit, chicken and shrimp. An international symbol known as the radura — a flower inside a dashed circle — is used to identify irradiated foods around the world. In Europe and the U.S., irradiation is prohibited under guidelines for producing organic foods, such as the sprouts implicated in the current outbreak.
The reason irradiation isn’t more widely used in the U.S. and abroad comes down to just one thing: consumer fear, said Patrick Wall, professor of public health and a food safety expert at University College Dublin in Ireland. “People hear irradiation and they think of Chernobyl,” Wall said.
But the tide of opinion may be turning, at least in the U.S., said Tony Flood, director of food safety at the International Food Information Council Foundation, a Washington-based nonprofit funded by food, beverage and agricultural companies. In a recent foundation survey, 60% of consumers said they were very or somewhat favorable toward the idea of food irradiation. And 54% said they’d be more likely to consume or purchase irradiated food if they knew it was safer than nonirradiated food.
The Organic Consumers Assn., meanwhile, says that the growing popularity of organic foods is proof that consumers don’t want irradiated foods.
Critics of food irradiation argue that the practice reduces levels of nutrients (such as vitamin C, folate and thiamine) and generates chemical compounds with unknown health consequences.
But these fears may be unfounded: A 1998 joint report by the World Health Organization, the Food and Agriculture Organization of the United Nations and the International Atomic Energy Agency reviewed more than four decades of study on irradiated foods and concluded that the foods were safe and nutritionally equivalent to other sterilized foods, such as items that have been canned or pasteurized.
(The report focused on foods irradiated with a dose of more than 10 kilograys, a unit that measures the amount of radiation absorbed by a kilogram of food. In the U.S., regulations limit the dose to between 1 and 8 kilograys for most of the approved foods.)
Critics also argue that irradiation does nothing to prevent the contamination of foods in the first place. The 2006 E. coli outbreak involved spinach that was contaminated by cattle feces from a nearby farm. The 2009 salmonella outbreak was traced to contaminated vats at a peanut-processing plant in Georgia.
Furthermore, irradiation is less effective against viruses, which are responsible for far more cases of food-borne infections than bacteria, according to an analysis by CDC researchers published in Emerging Infectious Diseases earlier this year. Nor is irradiation a foolproof way of eliminating all bacteria from treated foods, said Sarah Klein, an attorney with the food safety project at the Center for Science in the Public Interest, an education and advocacy group on Washington, D.C.
Klein acknowledged that irradiation would be a valuable tool to prevent food-borne illnesses. But, she added, “consumers don’t want food that’s been produced in unhygienic conditions and then nuked at the end. It’s not a silver bullet.”