Summary: Irradiated food will almost certainly become a larger and larger part of our supermarket food scape, although not all foods are suitable for irradiation.  It is entirely safe with regard to presence of radioactive particles, as the food is effectively being x-rayed-not having uranium sprinkled on it! The high energy particle passing through the food kill bacteria, enhancing food safety and extending the shelf life. Scientific studies are conflicting on whether food chemistry changes are of any great significance. Irradiation diminishes some vitamin levels to variable degrees. So long as irradiated food is labeled, we can chose ourselves whether to buy it. If the government chooses for us by refusing to mandate compulsory labeling, consumers will have to 'shut up and eat it', or turn to de facto standards such as 'organic' produce.

Background

In the end, we have to rely on rat studies, and well peer reviewed science. With the commercialization of science, it is less likely that long term studies will be done to establish long term effects of various compounds. In the end, it is up to the individual consumer to decide how much faith they have in government agencies pronouncements on safety.

These agencies very often rely on reviewing existing scientific studies. None of us have the time, and few of us the expertise, to find these studies, and critically read them ourselves. It is up to the government to find them; decide if the areas of concern have been investigated at all; if good and independent science has been done (read the reported results very critically); and decide if the results are clear and unequivocal enough to say that a chemical or process has no adverse effects on human health. And if there are minor effects, to say clearly what they are. And if it is unknown, say so.

And then it is up to us, the consumers, to make sure food containing such chemicals or so processed, is clearly labeled. Then we have the ability to make informed choice. The accepting risk is a personal decision, not a governmental or industry enforced 'choice'.  

How does it work?

Practically, it means passing food on a conveyor underneath a strong x-ray or gamma ray source . This is equivalent to the use of x-rays in medicine. The source must be a lot more powerful (100,000 to 3 million times the strength of a chest x-ray, for example), which means larger amounts of radioactive material must be used.
 
People talk of 'radioactive food', or 'nuked' food. In the mind of some, the food becomes radioactive by going through this process. This is dead flat wrong. The food is exposed to high energy rays from a radioactive source, but the rays pass right on thru and keep going. The source material is not applied to, sprinkled on, or in any way contaminating, the food. In the same way as you are not contaminated with radio active material when you have an x-ray, the food is also uncontaminated. You don't 'glow in the dark' after an x-ray, and neither does the food! The possibility of 'radioactive food' is an impossibility, a non-issue.
 

It may be safe, but are there any other issues?

Taking the last issue first, the argument is that if irradiation plants proliferate-especially if they become a virtual requirement for meat packing plants, for instance, there will be a problem safely disposing of the semi spent radio nucleotides. Because of the long life of these materials, safe storage will be a burden on society for many generations to come, and therefore responsibility for safe storage falls on the government, and such care is a subsidy to the plant operator (the operator doesn't have to bear the long term cost of securely storing the material until it is safe). In effect, because of the extraordinarily long life of the dangerous material and the relatively short life of most businesses, the business is able to avoid paying the true cost of doing business, but 'socializes' the cost of long term storeage-passes it on to present and future members of society. You can reasonably argue that the 'socialization' of some of the costs of doing business is relatively widespread, depending on the type of business and local environmental laws. The difference here is the long time horizon, stretching into generations.

Bacteria are living cells. How can they be lethally affected-killed-and the cells of the food on which the bacteria may be living remain unaffected? Logically, we must assume all living cells are affected by high energy radiation. But what are those affects? And are any of the affects dangerous to human health?

Here the water gets decidedly murky. There appears to be relatively little substantive body of peer reviewed and tightly scrutinized evidence one way or the other. A lot hinges on following animals (non-human animals) fed diets of foods that have been irradiated. There is never any immediate and obvious bad effect. The question then becomes the effect over time-a long term, slowly developing effect. The numerous studies done on rats and mice have shown, in some cases, lower birth weights, slower growth, chromosomal damage and the like, and in others, no effect at all. And here there appear to have been no long term studies on humans at all. Short term studies on human volunteers did not discover any adverse effect.
 
The most frequently repeated argument is that the high energy gamma rays create 'free radicals' in the cells they penetrate. Free radicals are implicated in heart disease. Antioxidants in fruit, vegetables, whole nuts and seeds protect against free radicals, as do supplements with vitamin E. However, the  'standard western diet' is very deficient in antioxidants compared to even an urban version of a natural gatherer-hunter diet. And the standard western diet increases the requirement for antioxidants. As does the stressful western industrial/urban lifestyle.

The counter argument is that our physiology is so challenged by vitamin and mineral deficient highly processed food, environmental chemicals from a huge number of sources, stress of all kinds, lack of exercise, and lack of whole natural fruit, vegetables, organ meats, sea foods, seeds, and nuts that we need to take protective supplements anyway. Even a few more free radicals can be dealt to by our vitamin E supplementation.

Another argument is that sometimes new compounds are formed, called 'radiolytic products'. Some argue that because these new compounds have not been encountered by the human organism before, we do not know if they could perhaps be toxic to some degree, or possibly even carcinogenic.

The counter argument says that somewhat similar compounds are produced in some other processed foods, and that any form of processing, including cooking, produces compounds not formerly present in the food.
 
The effect of irradiation on the vitamin content of food is also in question. Some of the B group vitamins, and vitamins A, C, E, and K are destroyed, depending on the dose rate and the susceptibility of the particular vitamin. And to that has to be added storage time (vitamins in fruit and vegetables, in particular, decline with time after harvest), and the usual vitamin loss in preparation (shredding, dicing etc.) and cooking.

The counter argument is a bit thin-namely that there is vitamin loss in all processing and cooking, so why worry about a bit more loss from an additional process? Fair enough if the west ate all natural food, in variety. But we don't.
 
The last  argument is that food poisoning bacteria could become resistant to irradiation over time, in the same way that over-prescription of antibiotics have slowly selected for antibiotic resistant strains of bacteria. If this happens, the dose of radiation, or length of exposure could be increased. Besides, food poisoning organisms are not controlled within the human body by irradiating people, so it is not as if we are losing a useful medical purpose. If organisms become immune to radiation, it would simply mean that the irradiation process could not be used any more.

Positive effects

There has been one instance, at least, where food rejected as unfit for human consumption due to high levels of contamination has been put into the human food chain after irradiation sterilized it.

The counter argument is that these are regulatory and control issues. That is, there will always be people who will attempt to 'cheat the system', no matter what it is. It is up to government to fund statistically valid sampling, and cunning, effective, and incorruptible third party or government inspectors to uncover such scams.

Irradiation has many benefits for retailers beyond food safety. Shelf life can be doubled. The shelf life of strawberries can be extended by at least a week, bananas by three weeks, and so on.  This means that meat, fruit, and vegetables that had to be discounted because they were close to the end of their shelf life can be offered at the normal price for longer.
 
For us consumers, it would logically mean that the time over which the vitamin content continues to decrease is longer.
 
Irradiation is an alternative to fumigation of seeds, nuts, fruits and vegetables that cross national boundaries (quite low doses are sufficient to kill insects). The gas methyl bromide has been the fumigant of choice in the past. It is an excellent insect killer, it is odorless, doesn't explode (unlike other possible fumigant gases), is relatively cheap, is heavier than air, and disperses very quickly after the fumigation time. There are no residues other than occasional small amounts of bromine in oily seeds or nuts. Unfortunately, methyl bromide has been implicated in damage to the ozone layer. While there is still argument about the role of naturally generated methyl bromide from the oceans, methyl bromide gas has never-the-less been placed on a 'soon to be phased out' list worldwide.
 
Most supply wholesalers automatically fumigate their sacks of peanuts, almonds, sesame seeds, rice and the like as part of good warehouse bug elimination practice. No-one wants to buy bags of nuts and seeds with weevils or moth larvae in them-no matter how nutritious they may be! Irradiation may be an economic alternative to fumigation.

Can all foods be irradiated?

Which Western countries allow irradiated food?

But even countries with a ban on importing irradiated food items make no requirement that imported food sterilized by irradiation be declared as such. In addition, from time to time, some ingredients, especially spices, in prepared food imported into those countries are quite likely to have been sterilized by irradiation.

So we consumers are likely to be buying more and more food items that have been irradiated.

Once again, it comes down to choice. If you have the money to prefer unirradiated food, then you can vote with your wallet if you have concerns about the nutritional diminishment of irradiated food. Equally, you may chose irradiated food preferentially where there are concerns about bacterial contamination in some classes of food.

Corrections, comments, argument and observations are welcome!

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