Radiation has a very bad reputation. There is something about it that scares the daylights out of people. This is understandable since the devastation of Hiroshima and Nagasaki produced graphic images of the devastation that radiation could cause. The Cold War generated additional fears of radiation silently killing off large numbers of people. Even today, one sees the fears generated by the phrase ‘dirty bombs’ that kill by nuclear radiation.
The latest issue of Physics Today (February 2012, p. 66) has an article by James W. Dixon, professor of animal science at Iowa State University, that looks at a question that troubles a lot of people: Should we be concerned that the food we purchase and eat nowadays may have been irradiated?
Dixon says:
Not surprisingly, the effect of radiation on food is related to the amount of ionizing energy absorbed. That quantity is measured in grays (Gy), named after physicist Louis Harold Gray, with 1 Gy being an absorbed dose of 1 joule per kilogram of material. Doses of less than 1 kGy prevent sprouting in potatoes and delay ripening of fruits. Such doses also serve to disinfect foods by killing insects in grains and fruits and inactivating parasites in meat—in particular, they can knock out the worm responsible for trichinosis.
Slightly higher doses of 1–5 kGy serve to pasteurize foods—that is, to kill many of the microorganisms that reside therein. Radiation pasteurization, or radurization, significantly reduces or eliminates bacteria of public health significance in the food. Salmonella, the most often reported bacterial agent of foodborne illness, Listeria monocytogenesi, and the harmful bacterial strain Escherichia coli O157:H7 are all very sensitive to irradiation.
What are the usual concerns that people have?
Perhaps the more prevalent concerns relate to the quality of the food after irradiation. Some consumers worry that irradiation will be used to “salvage” spoiled food, others are concerned that irradiated food is poor in nutrients, and still others express anxiety about compounds generated in food during the irradiation process.
Since irradiation reduces the amount of bacteria in the food, it increases shelf life. As noted earlier, though, the organisms responsible for food spoilage are not as sensitive to radiation as are more lethal bacteria such as Salmonella. In any event, spoilage results from bacterial byproducts, not simply bacterial presence; radurization, like conventional pasteurization, does not get rid of those byproducts. If irradiation were used in an attempt to salvage spoiled milk, for example, the process would not fool the consumer; the milk would still smell and taste bad.
He concludes:
For 30 years now, food scientists have been trying to determine whether irradiation creates any byproducts that are not caused by other common (and, by the way, rarely tested) processes. After three decades, we haven’t found any, though we can’t say with certainty that they don’t exist.
…
The scientific evidence to date indicates that irradiation does not produce any toxicity in foods. Still, consumers have the right to make their own informed choices. For the foreseeable future, consumers will retain the option to select nonirradiated foods; indeed, at present it’s the irradiated meat, poultry, or produce that is hard to find. In any case, shoppers can readily distinguish between the irradiated and nonirradiated varieties in the supermarket: Those foods that have been irradiated must, by US law, display the internationally recognized Radura symbol shown in the figure, accompanied by the words “treated by irradiation” or “treated by ionizing radiation.”
Although such food is required by law to display the ‘Radura’ symbol, I must admit that I personally have never seen it on any food I have purchased. Either irradiation of food that I happen to buy is rare or I am remarkably unobservant and incurious about the packaging of the things I buy and eat.
It is an interesting and informative article, though, that clearly lays out the issues.
A lot of supermarkets are reluctant to carry it because of (IMO irrational) consumer fears. The big supermarket around here, Wegmans, started carrying it and launched it with a bit promotion in their magazine, Menu, basically saying how you can now do all this stuff with like rare burgers and such and it’s totally safe because of the irradiation. Sorta neat, but since I usually try to buy locally produced meat anyway, I haven’t bought it myself.
I haven’t followed this question lately, but when the controversy erupted in the ’90s opponents of food irradiation made a big deal about “Unique Radiolytic Products”. URPs, they claimed, were distinctive molecular compounds seen only in irradiated food, which the FDA had declared itself uninterested in studying.
Dixon’s article says nothing about these (which, if they exist, may well lie beyond the competence of an “animal science” professor in the first place).
Nor does he address the prospects of contamination of food by leakage of whatever radioisotope it was exposed to during irradiation. His only consideration of accidents involves transport of said materials, in an exact echo of nuclear power/weapons industry propaganda that pushes my suspicion buttons.
Personally, I like the advice of a food guru whose name I’ve forgotten: “Eat nothing which has spoiled, and nothing which can’t.”
Actually, the article specifically refers to what you call URPs:
Many food scientists are chemists and are well trained in how to isolate and characterize chemicals, so your categorical dismissal of their expertise is really off base.
I don’t see how any radioisotopes could get into the food. There usually is some sort of barrier that blocks the source from the target. Anyway, I thought radioisotopic radiation was only for medical applications, and that they usually use electron or x-ray radiation, which would makes the whole point moot.
And finally, irradiated food can spoil. Haven’t you ever seen pasteurized milk spoil? It’s the same thing.
Hmm, I checked wikipedia and it says that “most” processors prefer Co-60 and not x-ray irradiation. Regardless, based on how the sources are kept, the possibility of the metal somehow getting into the food seems like the least concern.
Jared A -- Thanks for fact-based replies.
I was passing along what seemed to be potentially legitimate concerns from the early stages of this debate, not necessarily taking an unqualified advocacy position.
And while animals become food all the time, an “animal science” professor does not automatically qualify as a “food science” authority.
Some claims have been made about the spoilage-resistance of irradiated food going well beyond the benefits of pasteurization. Likewise, the anti-irradiation activists I knew described specific incidents of radio-isotopic leakage contaminating food, though I see no such claims on one such web page now.
Some of the other concerns raised (again, I don’t claim the technical knowledge to evaluate these):
Again, I don’t categorically assert these accusations are true. However, I have no problem in claiming that the claims of agribusiness corporations and the nuclear-anything industry should be viewed with reflexive distrust.
“An important 2001 study linked colon tumor promotion in lab rats to 2-alkylcyclobutanones (2-ACB’s), a new chemical compound found only in irradiated foods.”
So this would be a case of a URP! Sounds scary, but I too don’t have the expertise to evaluate this one, either. From my rusty organic chemistry I recall that cyclobutane based compounds are pretty unstable, so I find it believable that ionizing radiation might form it 2-ACB, but, again, don’t have the background to really judge that.
I strongly agree with your point about taking claims from agribusiness with a grain of salt. I would be inclined to also extend it to nuclear (anything) as you do, but from my perspective right now the nuclear power proponents tend to be more grounded in reality than the opponents (not that there aren’t selfish biases/lies on both sides.). But that’s off-topic.