Since the 1950s, a growing volume of radioactive waste from nuclear reactors has burdened present and future humankind with a monstrous millstone. The nuclear industry, in seeking community acceptance of its waste products, developed food irradiation (FI) technology as a means of using spent fuel rods. This technique, say nuclear proponents, can provide more food security for the world by eradicating storage pests in grain, by killing fruit fly in fruit, by preventing mould growth, by delaying ripening, by preventing sprouting of potatoes, onions and garlic, by extending the shelf life of meat, fish and shellfish … It's all safe and wholesome and it's only the built-in conservatism of consumers, we are told, that stops widespread benefits from this wonderful scientific advance in food technology.

However a comprehensive survey of FI research by Heimen Julius (Wellbeing Magazine No. 65) might inspire less confidence in this "techno-fix" approach to the problems of adequate food security for the world's people.

FI requires food to be exposed to high-energy wave particles (similar to having an X-ray but much stronger.) It uses ionising radiation, and its plants should have similar safety provisions to a nuclear reactor. Doses are measured in kilograys (kGy). 1 kGy equals 100 kilorads (krad).

FI and grain foods
Many different insect pests can infect grains, and a 0.75 kGy dose of irradiation is supposed to kill them all. However, some insects require much higher levels of irradiation.

An example is Rust-red Flour Beetle (Trilobium castaneum) which is sterilised after bombardment with 0.8 kGy, but with a mortality rate of only 15%. The eggs, larvae and pupae are radiation sensitive, but the adults are radiation resistant.

If 0.75 kGy dose is insufficient to deal with some grain pests, why not simply increase the dose? The answer comes from ANSTO, the Australian Nuclear Science and Technology Organisation. Evidently the viability of cereals is seriously adversely affected at such proposed radiation doses. More irradiation would probably kill the grain. Hence FI advocates only refer to pests that are radiation sensitive - and keep quiet about the rest.

What if irradiated grain is subsequently exposed to un-irradiated pests in the course of transport or storage? French research indicates that these pests can thrive! Grain Weevil (Sitophilus granarius) found in irradiated wheat produced significantly more offspring than weevils reared in un-irradiated wheat.

Julius quotes other examples of this phenomenon, which indicates that irradiation of grain is only effective with radiation-sensitive pests, leaving radiation-resistant varieties free to prosper.

What about food moulds? These thrive when moisture is present, and can produce toxins and aflatoxins. Indian research has shown that toxin production on irradiated commodities was much higher than on un-irradiated commodities. French research indicates that irradiation causes a breakdown of fats into free fatty acids which stimulate aflatoxin production. FI actually changes the chemical composition of food which, if subsequently affected by moisture and mould, can develop much higher toxin levels. Another problem may occur when irradiated moulds grow on un-irradiated commodities, increasing their toxicity.

It seems that grain irradiation produces more problems than it solves.

Irradiating Fruit
Do irradiated fruits fare better? In the case of citrus and stone fruit, the doses required to inactivate moulds are higher than the fruits can tolerate. A dose of 2 kGy+ is necessary to control Grey Mould (Botrytis cinerea), the major decay mould of strawberries, and a 3 kGy+ dose to control "Leak Disease" (Rhizopus stolonifer). Irradiated strawberries can deteriorate with an off-flavour, bleaching, and watery centres developing. There is a similar story with some varieties of grapes which require a 10kGy dose to deal with Grey Mould, much in excess of what the fruit can tolerate.

The biggest berries, tomatoes can suffer rot from Alternaria, requiring a dose of 3 kGy+ to control. However many tomato varieties can only tolerate 1 to 1.5 kGy doses. Higher than this, and tissue softening results just as the tomatoes are to be transported.

Can food irradiation help control insect pests in fruit, many of which are firmly established in Australia? Doses in excess of 1 to 2 kGy are needed to kill most eggs, larvae and pupae of these pests, although 0.8 kGy is sufficient in the case of Queensland Fruit Fly. Quarantine regulations require all living stages of pest species be killed. It is difficult to assess whether all living specimens have been effectively irradiated in fruit. Different dosages apply to different fruits, and even low doses damage many fruits unacceptably.

Delayed ripening is another supposed benefit of FI. Consignments of bananas need 0.3 to 0.65 kGy dosages, but many banana varieties would be damaged at this level. Pears can tolerate about 1 kGy, but require about 2.5 kGy to inhibit ripening. To beat skin scald and brown cores with ripening, apples need 1.5 kGy, which would harm many varieties.

Each fruit variety is a separate case as far as FI goes - although proponents of the technology try to generalise the supposed benefits to fruit production and consumption.

Can FI prevent sprouting of potatoes, onions and garlic? Some varieties of irradiated potatoes and onions are more inclined to rot. However garlic can tolerate FI quite well.

Other foods
Should we rely on FI to extend shelf life of meat, fish and shellfish? Radiation-sensitive, food spoiling bacteria (from the Pseudomonas group) assist in rotting and produce bad smells, but the bacteria themselves are harmless. The putrid smell indicates good conditions for bacterial growth, meaning odourless food poisoning bacteria, usually Salmonella, could multiply. If the "pseudomonas" have been irradiated, there will be no smell to warn consumers that food poisoning may have occurred. Some Salmonella bacteria are recovered after FI with 9 kGy - so why not zap these foods with that dosage or even more? At much lower dosages (2-3 kGy), unacceptable changes to smell and taste of steak, chicken and unpeeled shrimps occur. Another problem - the near-to-anaerobic bacteria from the Clostridium botulinum group, produce the botulinum toxin, deadly in the smallest quantities. It is extremely radiation resistant. Think of all that vacuum-packed fish…

Implications for your Health
Are there long term health implications from eating irradiated foods? Many adverse effects show up in mammals fed irradiated food for a prolonged time: lowered immune resistance, decreased fertility, damage to kidneys, depressed growth rates, Vitamin A,B, C, E and K deficiencies, as well as a surge in polyploid lymph cells. These findings are backed up by other research in which human lymph cells were brought into contact with irradiated sucrose solutions. Extreme toxicity followed, cell divisions were inhibited, chromosomes appeared shattered, and four times the normal level of polyploids were evident.

The FI lobby emphasise that irradiated food cannot be radioactive itself, but what of radiomimicry? Several researchers have noticed similarities in the effects of eating irradiated food for prolonged periods, and the usual after effects of exposure to radiation. The symptoms look like damage from free radicals, which may result from severe chronic Vitamin E deficiency. The good results of feeding trials achieved by FI advocates could well have had much to do with the generous amounts of anti-oxidants added to the diets of their experimental animals. Anti-oxidants are free radical scavengers.

Conclusion
As the nuclear industry is the main proponent of FI, are we cynics if we ask if its stance might have more to do with nuclear waste disposal than health, food safety and security? As food irradiation appears to be counterproductive in producing the latter, one would have to assume that the former is the real objective of the nuclear barons.

• Compiled by Judy Blyth