LURKING DANGER?: Irradiation is commonly used to preserve certain foods and destroy insects and germs in others, but it may not work well in all products--or on all pathogens.
© ISTOCKPHOTO/ROEL SMART

The four-month-long, nationwide salmonella outbreak from peanut butter—coming on the heels of other, widespread food-borne illnesses—raises the question: Why not just zap all of our food with radiation to destroy contaminants?

The U.S. Food and Drug Administration (FDA) last summer okayed irradiation to destroy pathogens in fresh iceberg lettuce and spinach in the wake of an Escherichia coli (E. coli) outbreak traced to the latter in 2006. Since the early 1980s, irradiation has also been approved for that same purpose in meats as well as to both extend the shelf life of and kill insects in fruits, veggies and spices.

But radiation isn't commonly used to treat most foodstuffs in the U.S. because of cost, consumer wariness and the worries of some about its long-term safety. Food & Water Watch (FWW), a Washington, D.C.–based advocacy group, frowns on the process, which it says degrades the nutritional value of foods and has the potential to mask but not remedy unsanitary conditions at plants that led to it in the first place.

We asked Sam Beattie, a food safety extension specialist at Iowa State University in Ames, to fill us in on the controversial process and why it hasn't been used more often, especially in light of the recent deadly outbreaks. There is an irradiation facility at the university, but it's used only for studies and Beattie, a microbiologist, has no affiliation with companies that make irradiation devices or zap their food.

[An edited transcript of the interview follows.]

What is food irradiation, and how does it work?
Irradiation is done by exposing food or bacterium to a dose of ionizing radiation, which disrupts the DNA or protein of pathogenic bacteria that make people ill.

When we talk about the sources for irradiation, we're looking at two major ones: radioactive elements—like cobalt 60—and the electron beam, or e-beam. Cobalt 60 is an isotope, or a traceable radioactive version of the element, that emits the type of radiation called gamma rays, whereas the e-beam is an electron-based radiation source. We also are experimenting now with x-rays, which are generated from an electron beam hitting a piece of metal, as a potentially new technology for irradiating food
 
The potential problems of the irradiation processes are fairly limited. As cobalt decays, it becomes less effective, so you have to monitor that. E-beams don't penetrate as deeply as cobalt, so you have to irradiate less of a food at a time. And generating x-rays takes an extra step, so it may not be as efficient as e-beam.

Cobalt 60 has historical precedence with food. It's been used for a long time with meats, fruits and vegetables. It is a safe source: When it decays, it becomes a stable, less radioactive element — in this case nickel, so disposing of it is less of a problem than with isotopes used at, say, nuclear plants. And there is no direct contact between the cobalt and the food or its packaging.

How long does it take to zap bugs in food?
It depends on the kind of radiation you're using. Cobalt 60 is a lower dose rate, so it takes longer—a minutes type of exposure. E-beam is a more intense, higher dose rate and we're looking at seconds.

Which foods is irradiation most used on?
Among fresh produce, the FDA has only approved irradiation to reduce food-borne illness in leaf spinach and iceberg lettuce. We're not exactly sure why only those two, because there's very little difference between cut greens when it comes to whether or not they turn to mush under an e-beam at the approved levels.