Unpredictable and incalculable health risks of food irradiation

I. INTRODUCTION
The irradiation of foods is demanding increasing attention all over the world. It is increasingly advocated and promoted, especially by technology and industry. Considerable financial and personal resources have been invested to develop powerful irradiation plants, and ample experience has been gained in the technology of irradiating various food groups. The respective references include many thousands of single titles.

The accumulation of considerable and ever-increasing quantities of radioactive waste from nuclear plants essentially makes the establishment of cheap irradiation plants possible, and keeps the cost of irradiation low. The producers and distributors of foodstuffs are expecting profitable future developments by this method. In some countries, e.g. the USA and Canada, specific foods intended for the market and consumption have already been released for irradiation.

Technology and industry are getting more emphatic in their demand that the authorities responsible for public health should release foods for irradiation, or that approved releases should be expanded. Because of the substantiation of suspected health risks associated with some irradiated foods, according to the present state of information, such a release was permitted only hesitantly, for good reason, and in varying degrees in the respective communities. An increase in such releases is to be expected in the near future.
A release presupposes an adequate comprehension of the connected health risks. It must however be stated that the scientific information concerning such risks is still very fragmentary, even with respect to some releases already made in certain countries, if the appropriate strict standards were applied. At present, the known facts principally demand caution in this respect. Furthermore it would be wise and appropriate to treat scientifically-undecided problems so that all decisions adopt the precautionary principle in consideration of safety.

Biology and medicine do not basically reject research in the field of food irradiation. But economic considerations and propaganda, as well as the admittedly vague hope that the irradiation method might eliminate the adding of toxic chemicals to foods, must not conceal the risks of food irradiation to human health.
Biologists and physicians observe with increasing anxiety the growing disproportion between the efforts to advance and promote the technical and economical aspects of food irradiation on the one hand, and the efforts to comprehend its biological and medical risks on the other.

The disproportion is already demonstrated dramatically by the respective financial resources invested in the relevant research on both sides. It is also characteristic that technical themes predominate at meetings and symposiums, while too few hygienists, biologists and physicians are called upon to speak critically.
In the light of these developments, the responsibility for the maintenance of public health obliges biologists and physicians to point out more emphatically the complex of possible biological risks which may be associated with the consumption of irradiated foods.

The following detailed discussions present a factual, and equally urgent, scientific outline of the objections of biology and medicine to the irradiation of foods.

II. THE NATURE AND DEVELOPMENT OF FOOD IRRADIATION
1. Responsibilities for the preservation of fresh food

Stored foods are subjected to processes which eventually induce their decay.
These processes include:

1. the physical and chemical reactions in foods
2. the attack and activity of microorganisms or insects in stored material.

Generally, not only untreated, but to a certain degree also treated foods, are subjected to such physical and chemical changes. Enzymatic processes are a primary contributor to these changes. With the conventional methods of treatment and storage, e.g. by refrigerating, an attempt is made to at least retard such enzymatic reactions.In most cases, microorganisms effect a particularly rapid decay of foods. Often this cannot even be prevented by cold storage. Through sterilization or pasteurization - i.e. primarily with heat treatment, by adding salt, sugar, and by smoking - an attempt has been made to kill or considerably reduce the original number of microorganisms in food, and to inhibit their rate of growth.
Attack by insects reduces the storage capacity, especially of wheat, flour, peas, beans and dried fruits.
For the purpose of combating pests and microorganisms, chemical substances - in solid, liquid, or gaseous form - are frequently applied, whereby toxic agents which are harmful to health may in some cases be induced into foods.
Food irradiation, a new branch of applied nuclear technology, is being planned as a new process of food preservation.
For this purpose, ionizing radiation is applied - either released by large apparatus like particle-accelerators and X-ray installations, or, as in most cases, through the nuclear decay of the radioisotopes found in atomic waste and reactors.
Contrary to heat and chemical processes - and this deserves special emphasis - energetic radiation affects the molecule in a very specific and highly interventionary manner. It establishes so-called "excitated conditions" and causes the formation of "radicals" or ionization. The molecules and atoms, changed in this manner, are chemically highly-reactive, and effect specific changes which are only partially effective with respect to the preservation of foods. However, on a large scale, they effect qualitative changes, which are extremely dangerous with respect to health, in foods - also partly dependent on the dosage.
In spite of the specific quality-reducing effects of energetic radiation on treated foods, and many of its actual and/or possible biological risks from consumption, food irradiation is often advocated with alarming indifference by technology and industry.

The following arguments presented in favour of food irradiation, which are partially justified, and partially ignorant of the actual situation, are:

a) The technical aspect of food irradiation is relatively simple.
In fact, various types of installations have been developed, which provide for treatment on a large scale, and subject approximately four tons of food to irradiation per hour.
b) Radiation sources are cheap since they can be obtained from the radioactive waste of nuclear technology. Accordingly, the operating costs of irradiation are kept low. Actually, it is stated that the inhibition of germination in one ton of potatoes by irradiation would cost only 15 pfennig/kg., and for the sterilization of food, approximately 2-8 pfennig/kg.
c) Furthermore it is already possible to irradiate foods in the containers in which they are stored and sold. However in this respect, one too readily ignores the fact that many packing materials suffer structural changes when irradiated, and become permeable to air, thus endangering the durability of the enclosed foods or even delivering toxic substances to the food.
d) In addition, it is pointed out that, in the case of irradiation, there is hardly any rise in temperature, and that consequently, none of the usual heat changes takes place.
It is true that even with high X-ray doses, the resulting rise in temperature generally does not exceed
10°-15°C. However, this asset should not make us overlook the fact that in many cases irradiation induces much more drastic and biologically harmful changes than has ever been the case with heat sterilization.
e) Food irradiation is also of interest from the hygienic perspective.
It helps destroy pathogenic germs in foods, e.g. Salmonellae, and thus, helps to combat infectious diseases and pests. Through the destruction of Clostridium botulinum and its spores, the incidence of poisoning caused by Botulinus toxin in spoiled food was reduced.
However, a logical investigation of the facts reveals that these hopes were premature, because, to name one reason, the different types of microorganisms vary considerably in regard to radiation sensitivity, contrary to heat sterilization. And their respective spores are generally even more resistant to radiation than the living germs. Therefore it is definitely possible that in certain cases particular species of microorganisms survive to a certain degree.
Furthermore it can happen that, within one single species, highly radiation-resistant biotypes are selected out, or newly formed by mutation, and result in the breeding of an entirely new micro-flora. In the case of Clostridium botulinum, it could be especially hazardous if a sufficient number of this particularly radiation-resistant type remained in the food after irradiation, able to reproduce and form toxins, while other germs are destroyed. In this case, which is definitely not hypothetical, the spoilage of the conserve is not externally recognizable, due to the lack of gas development and bombage. The conserve would nevertheless appear flawless in spite of Botulinus toxin, which develops without the formation of gas, thus posing extreme danger to the consumer.
In conclusion, it should always be kept in mind that extremely high radiation doses are required to achieve an adequate destruction of the germs in foods. This results in the concentrated formation of toxic, organoleptic odor-and-flavor-destructive substances in foods when irradiation is used for sterilization, and partially also for pasteurization.
f) With preference it is pointed out, especially in view of the warnings and criticism from the medical and biological fields, that irradiation of foods may eventually forego treatment with chemicals, which are otherwise indispensable for preservation, and that these foods thus remain free of additional poisons. It is only natural that the prospect of eliminating treatment and contamination with insecticides and pesticides, that might otherwise be necessary, in favour of irradiation, is of interest to the community. Unfortunately, the hope of protecting foods from poisons by using irradiation has to be discarded or decidedly reduced, because often it is to be anticipated that the toxic substances induced in foods through irradiation are biologically more questionable than a large number of other chemicals. In addition, it becomes increasingly more apparent that the preservation of foods by irradiation often requires the combination of irradiation with other methods of preservation. For this reason, irradiation is not only combined with heat or cold treatment, but increasingly, also with the addition of different chemicals. Some of these chemicals are entirely inappropriate as far as their biological properties are concerned. With the additions of these chemical substances, an effort is made to intercept radicals, to combine with quality-reducing odor and flavor agents, to increase the radiation-sensitivity of bacteria and tissues, and to reduce the formation of toxic substances. Some of the additives are: nitrates, nitrites, antibiotics, reducing compounds and antioxidants, chloride, hydrosulphides, ascorbates, etc. In order to restrict the autolytical processes, i.e. processes surrounding decay in irradiated meat, it is furthermore proposed to inject the slaughter-animals with adrenalin
g) Finally, with alarming bravery, a picture of a universal food industry, designated by the irradiation of foodstuffs, is presented, without hardly considering the health-political arguments and limitations. Some of these industrial programs remind us more of some science-fiction fantasy, rather than of a logical program pertaining to facts. It could be very dangerous if, under the suggestive influence of such a global, economy-centered, futuristic picture, which promises high profits, the general public were to become increasingly blind to the health hazards connected with the consumption of irradiated foods. Who could resist the prospect of possibly prolonging the storage time of papayas by four days by means of irradiation, and thereby increasing the income, alone for Hawaii, by approximately 70 million DM? And who would not be impressed by the prophecy, although vague and heedless of the hygienic realities, that food irradiation will make a decisive contribution to world nutrition, in view of the daily increase of humanity by 180,000 persons? Due to the general efforts to raise the level of economy and living standards in the developing countries, only a small minority is aware of the health risk connected with using food irradiation in these efforts. The following specific expectations arise from the futuristic visions of materialistic developments, however very often disregarding the problem of biological risks:
With applicable irradiation dosages, the ripening can be inhibited in a good many agricultural and horticultural products, whereby the storage time and the marketing capacity can be prolonged e.g. fruit and vegetables and maritime products.
In certain cases, irradiated eggs and frozen fish are preserved for weeks instead of days, as was the case until now. The radius of distribution for products irradiated in such a manner becomes larger. New or unusual products become available in regions where they had not been marketed before, e.g. fish in the inland, Hawaiian products all over the world. The transport of irradiated and longer-storable products is facilitated and economized, due to the possibility of replacing airplanes with ships and railway as the means of transportation. Qualitative and weight losses are reduced, e.g. in potatoes and onions by inhibiting germination, and in wheat, flour and dried fruits by forestalling attacks by insects. Animal fodder is also preserved by irradiation.

2. On the history of food irradiation
The methodology and apparative stipulations for food irradiation are closely connected with developments in the physics of energetic radiation. The foundation was laid by the discovery of X-rays (by Rontgen 1895), of nuclear radiation (Curie, Rutherford a.o.), and of cathode rays (by Thomson 1897). Decisive new possibilities were opened by developing particle accelerators (1930-1940), e.g. Van de Graaff's apparatus, with which corresponding doses of highly energetic rays can be produced.
The impetuous advance of nuclear technology since 1937, and especially after the war, gave new impulse to the concept of food irradiation. In the reactors, increasingly larger amounts of waste radioactive material are produced, which become available as cheap sources of high activity for irradiation plants. Furthermore, additional radiation sources for such irradiation plants; e.g. cobalt-60, can be produced in the neutron flux reactors.
Basically, it has been known since the turn of the century that energetic rays, like X- or nuclear rays, can destroy living tissue, and consequently also microorganisms. During the past decades, appropriate patents for food irradiation were granted in various countries. However, widespread economic interest in food irradiation was stirred up e.g. in 1943, when sausages were conserved with the help of Van de Graaff's accelerator, or with large size X-ray apparatus, or by applying nuclear radiation from radioactive isotopes.
Soon after the war in 1945, scientific institutes and industrial firms in various countries, particularly the U.S.A., launched an extensive program of food irradiation for preservation purposes. Since 1950, the Atomic Energy Commission took a renewed interest in these efforts and supported them. In 1953 a special program was started on a large scale by the U.S. army.

Plants intended for food irradiation were built in various countries. These plants work partially with accelerators, partially, and recently increasingly more often, with radioactive isotopes. During the past decade, increasingly more attention was paid to these problems, not only in the U.S.A. (centers in Brookhaven, Massachusetts, California), but also in non-European and European countries. We refer to England (Aberdeen, Wantage), Scandinavia (Riso, Roskilde, Stockholm), Austria (Seibersdorf), Holland (Wageningen), France, Belgium, Russia, Poland, etc.
In the Federal Republic of Germany, the Federal Institute for Food Preservation has conducted corresponding tests since 1958. Since 1966, a large special institute exists within the Nuclear Research Centre in Karlsruhe.
A number of organizations and sub-organizations of the United Nations have taken an active interest in food irradiation. Of particular mention are the Food and Agriculture Organization of the UN (FAO), as well as the International Atomic Energy Agency (IAEA). The activities of these organizations concentrate mainly on the technological and industrial aspects. The interest of the World Health Organizations of the UN (WHO) dwindled more and more, in spite of praiseworthy individual efforts. However, in 1961 and 1964, the conference of experts of the FAO, IAEA, and WHO (16 members from I0 countries) presented a joint report on the problems, including the suitability for consumption, and legislation in the field of food irradiation.
The Technical Basis for legislation on Irradiated Food. Report of a joint FAO/IAEA/WHO Expert Committee. Rome,
21-28 Apr. 1964. 54 p.
However, detailed particulars concerning the hazards connected with the consumption of irradiated food were only inadequately presented.
On the other hand, the IAEA, together with the FAO, has recently taken an active role in the problem of applying food irradiation in developing countries, and published a report on the subject.
Application of Food Irradiation in Developing Countries. Joint FAO/IAEA Division of Atomic Energy in Agriculture. Technical Report Series No. 54. 183 p (Vienna 1966).
Furthermore, European industrial communities, e.g. the OECD and Euratom, are taking an interest in the inquiries. In February 1967, Euratom renewed its efforts - upon the urgent recommendation of a larger study group from six countries of the European Atomic Community - to support the industry with all the appropriate initiatives and to develop further and improve the technique of conserving with radiation. A selected group was instituted to work out recommendations on the problem of allowing irradiated foods (potatoes, strawberries, other fruits, etc.), for the six governments of the Atomic Community (which includes the Federal Republic of Germany). In this connection, the information and support measures intended for the industry, as well as the activities of the bureau Eurisotop of Euratom, are considered to be of the utmost importance. It makes us somewhat skeptical that these recommendations and support measures exclude the vitally important risk factors resulting from the intake of irradiated foods.
The anxieties of biologists and physicians are additionally confirmed by the fact that at a large symposium on food irradiation, held in Karlsruhe from May 5-10, 1966 (the FAO and the IAEA were invited, but not the WHO), the participants consisted mainly of representatives of industry and the economy.
3. Review of the experimental development or already applied possibilities of food
irradiation presently discussed.
a) Extending the preservation of foods by sterilization, pasteurization, and by the inhibition of metabolism and germination.
aa) The sterilization of foods requires relatively high radiation doses (for bacteria I-5 Mrad1, for virus 5-10 Mrad), which generally induce considerable qualitative losses in all treated foods, and leads to the formation of explicitly toxic products.
bb) Pasteurization has the solitary aim of reducing the number of germs. Subsequent cold storage prolongs the durability of treated foods. Pasteurization through ionizing radiation require radiation doses varying between 0.1 and 1 Mrad, which have a more or less drastic effect on the quality of the food
cc) Metabolic inhibition and increased durability connected herewith, especially in fruits and vegetables, can generally be attained by a partial inactivation of the enzymes. Since a total inactivation of the enzymes would require doses ranging from 5 to 100 Mrad, i.e. a radiation quantity that destroys quality, it can practically be eliminated. Therefore, only a partial inactivation is attempted with relatively low radiation doses, with only a subsequent insignificant prolonging of the conservation time. The application dose was as follows: for pears 0.2 to 0.4 Mrad, for apples up to 0.5 Mrad, for citrus fruits up to 0.3 Mrad, and for strawberries up to 0.4 Mrad
dd) Inhibition of germination, e.g. in potatoes and onions, can also be achieved primarily by inactivating germination-inducing enzymes. The doses required for this purpose range from 4 to 20 Krad.
b) The control of pests and parasites

By irradiating with the required doses, the aim is to prevent attacks by insects in stored wheat, in peas, beans, flour and dried fruits, as well as to control parasites like Trichinelle and Taenia in meat and meat products. The control of insects is possible, either by killing the mature animals or their eggs, with irradiation. Another possibility is to sterilize mature animals with appropriate low doses to prevent reproduction. For the destruction of insects, 25 - 100 krad would be required for a one-week radiation; 500 krad would be required for a one-day radiation. Insect eggs would require about three times this dose. For the sterilization of mature animals, 10 to 20 krad will generally be sufficient. In the practice of wheat irradiation, doses ranging from 10 to 50 krad are mostly applied.
In the case of Trichinella, a destructive dose be 10-30 krad. For the destruction of the Trichinella larva, 15 krad would already suffice. Worms, worm eggs and worm fins are treated with 20-25 krad.
c) Hygienic measures to control pathogenic germs by irradiation.
In order to reduce Salmonellae by I07, egg powder is treated with about 700 krad, and the frozen egg with approximately 400 krad.

In order to eliminate Clostridium botulinum2 from foods and prevent the formation of Botulinus toxin, one should attempt to reduce the germs together with their particularly radiation-resistant spores by I017.
Depending on the foods being treated and the radiation doses applied, qualitative changes take place; the toxic character has been proven in specific cases, and the biological risk of a good number of these qualitative changes are still unknown. The following pages attempt to discuss such changes in accordance with our present knowledge.

III. EFFECTS OF IRRADIATION ON THE CONTENTS OF FOOD

1. Proteins
The influence of radiation on albumin (proteins and proteids) in food causes the separation of lateral chains and end groups of these molecules. The separated groups include, amongst others, amino acids, which suffer additional disintegration under the influence of irradiation (radiolysis). However, considerable quantities and varieties of hydrocarbons are formed, partly volatile in nature. Methyl and ethyl-mercaptan, dimethyl- and carbonyl-sulphine, hydrogen sulphide, benzol, toluol and methane are found, amongst others. (MERRITT, 1966).

2. Amino Acids
Especially sensitive to radiation are those amino acids which contain fissionable lateral chains or sulphur (HILL etc. 1964).
The individual amino acids in foods are disintegrated in a specific manner when exposed to irradiation, according to the chemical synthesis, e.g. phenylalanine disintegrates to form toluol and benzol, and tyrosine to form phenol and cresol.
From cysteine and methionine, sulphides, methylmercaptan, sulphur dioxide and hydrogen sulphide are particularly formed. Through the disintegration of amino acids caused by radiation (radiolysis), considerable amounts of carbon dioxide are generally released. (MERRITT, 1965 and 1966).

3. Fats and Fatty Acids
Fatty acids are relatively sensitive to irradiation. Therefore the decomposition products of irradiated oils which are used for consumption require special attention. The quality of oil suffers enormous changes at medium irradiation doses, and even more so at high doses. Dependent on the dose, pronounced toxic substances are developed. Soya oil, especially rich in unsaturated fatty acids, showed multiple irradiation-induced changes when irradiated with a relatively high dose, e.g. changed iodine number, rise in the peroxide and acid values, destruction of tocopherol [Vit. E] (LANG et al., 1966).
4. Lipids
The lipids, related to the fats with regard to their chemical synthesis, and essential for the organism, are also extremely sensitive to radiation. The decomposition products of lipids are especially responsible for the changes in irradiated meat, as well as for its repulsive irradiation odours. The lipid molecules are separated by ionizing radiation through dissolution of their molecular bindings. Amongst others, chemically-highly-reactive, so-called radicals are formed, which, when combined with oxygen, can form hydrogen peroxide, amongst others. More than 80 mainly volatile compounds of lipids, disintegrated by irradiation, were analyzed. Particularly numerous are the carbohydrates, which themselves again can be disintegrated into highly toxic substances when subjected to irradiation. In many cases, these substances have not yet been chemically identified. In the decomposition products of lipids, 15 different aloanes, 13 different alcenes3, especially olefine compounds, furthermore methylesters, methylacetates and acetone are found. (MERRITT, 1965, 1966).
5. Carbohydrates
From the biological and medical standpoint, the products of radiation-disintegration of the carbohydrates in foods should be judged with particular caution and reserve. Included in these products are substances which injure the cell division and most probably also the hereditary structures, among others. Only a few of these substances are chemically known. The majority of these compounds produced by radiation, which have not yet been defined, were chromatographically determined. However, they have not yet been chemically analysed (HOLSTEN, 1965).
6. Nucleic Acids
It is an established fact that the nucleic acids (deoxyribonucleic acid, ribonucleic acid) are the carriers of the basic processes of life. They carry genetic information, are the basis for cell divisions, and thereby also for the growth and development of organisms, and they steer the fundamental biological processes in the cell. Nucleic acids are not only extremely sensitive to ionizing radiation, but also to the irradiation-produced chemicals in foods, e.g. irradiated sugars - and consequently suffer very drastic injuries in their synthesis. The ribosomes in the cells, i.e. the sites of transmission of genetic information of nucleic acids to specific protein molecules, are particularly sensitive to such products of radiolysis formed in the cells (HOLSTEN, 1965).
7. Enzymes
In order to destroy enzymes (large size molecular proteins with catalytic qualities) by irradiation outside their biological binding, very high radiation doses are required. However contrary to this, the inhibition of germination (steered mainly by ferments) and of sprouting in potatoes and onions, require relatively low doses. Cytochromoxydase (a respiration enzyme transmitting oxygen) in potatoes is already changed by 10,000 rad. The unchanged, or insignificantly changed, enzymes in irradiated foods often develop a particularly high activity. Thus, for example,. the enzymatic decomposition of meat is considerably increased after irradiation. It is therefore proposed to treat slaughter animals whose meat is intended for irradiation with adrenaline, in order to reduce the action of the ferments which dissolve proteins.
8. Vitamins
Similar to many other methods of food preservation, irradiation also destroys the vitamins in the irradiated foods to a certain degree. The reference that the respective vitamins could be added artificially afterwards does not satisfy in any way, since it has been shown that the biopotency, particularly of the fat-soluble vitamins, is reduced in this case. Furthermore, an essential difference has been determined between the addition of vitamins to irradiated foods, and the addition of vitamins to foods which had not been irradiated (RITCHEY et al., 1960; READ et al., 1961).
9. Formation of so-called radiomimetic substances.
So-called radiomimetic substances can be formed in irradiated food, i.e. compounds which have an effect on living tissue essentially similar to that of direct exposure to ionizing radiation. A group of such substances, so-called epoxides, were determined in irradiated foods.
10. Organoletic qualities (Changes of odour and flavour)
The external factors that are primarily responsible for limiting the trading and consumption of irradiated foods are the changes in odor and flavour caused by irradiation. These are called organoleptic changes. Depending on the kind of food irradiated, radiation - frequently at doses much lower than those required for sterilization (3-5 Mrad) - cause such undesirable changes that the product is rejected by the consumer. Unbearable changes generally already occur in milk and cheese after irradiation doses of less than 0.1 Mrad.. In the case of eggs, the limit is 0.3 Mrad; for bread and haddock, about 0.5 Mrad; for mutton and beef, as well as herring, it is approximately 1 Mrad; for ham, bacon, spices, corned beef, mackerels, about 1.5 Mrad; and for vegetables, pork and fowl, it is about 2 Mrad.
11. Textural (Tissue) Changes
Irradiated foods change their texture to a certain degree. This is caused by changes in the cell membranes due to irradiation, as well as to disturbances in the mineral metabolism, particularly of calcium metabolism, in the vicinity of these membranes. The large size molecules of the cell walls, as well as the permeability of these walls to the different ingredient substances of the cell, are especially sensitive to radiation.
Since the permeability generally increases under the influence of radiation, the internal cell turgot usually decreases simultaneously. At the same time the adhesion of the cells to one another is reduced. Increased respiration within the cell furthermore increases detrimental changes in the texture of irradiated foods.
12. Induced Radioactivity in Irradiated Foods
If foods are irradiated, nuclear reactions result in the formation of artificial atom types, depending on the kind, the energy, the amount, and the efficiency of the radiation dose applied, and on the radiation conditions. Some of these atom types are radioactive. Such radioactivity of initially non-radioactive atoms within treated foods not only develop if neutrons are used as the radiation source, but also if electron accelerators with high energy (10-20 Mcr)4 and high doses (15 Mrad) are applied for irradiation.

By consuming foods irradiated with the effective dosage, these artificially-produced, radioactive atom types enter into the organism and can be incorporated as "internal radiation sources". It can be stated that, where this occurs, insufficient attention has been paid to the biological-medical aspects of such additional radioactive isotopes. Often these artificial radio-isotopes are evaluated separately, and not in combination with the remaining artificial and natural radioactivities, or with the total radiation load to an organism. Too little attention is often paid to the composition of the food, and to the different conditions with respect to the age and sensitivity of the consumers. The evaluation is not taken seriously enough if, following the recommendations of the International Commission for Radiation Protection (ICRP) for the maximum permissibility of radioactivities in water, henceforth also artificial radioactivities in irradiated food in quantities up to 10-7 ici per gram of food are permitted, without the necessary criticism. Barely a note is made of the fact that artificial radioactive atom types can intensify themselves biologically through the food chain and reach the individual with respectively higher concentrations. It is seldom taken into account that, not only artificial radioactive atom types are formed, but that also neutrons are released, which induce secondary reactions whereby previously non-radioactive atoms are activated. Certainly many of the radioactive atom types which are formed in foods by the required irradiation dose have a relatively short life span, and disappear almost entirely from the irradiated foods within a few days as a result of natural radioactive disintegration. However, depending on the character and elementary composition of the foods, radiation treatment may sometimes induce the formation of a large number of long-living, radioactive isotopes, which definitely deserve attention. These include, among others, sodium-22 with a half-time5 of 2.6 years, which is formed during irradiation in accelerators for the sterilization purposes, in quantities ranging from 0.2 to 2 pCi, in one gram of meat. In meat and vegetables, phosphor-32 and phosphor-33 often dominate after irradiation. Further attention should in some cases be paid to calcium-45 (half-time 160 days), as well as rubidium, furthermore manganese-54 (half-time 291 days), iron-55 (half-time 2.6 years), zinc-65 (half-time 245 days) and particularly sodium-24 which, although it only has a half-time of 15 hours, is formed in considerable quantities in irradiated foods in accelerators, particularly in meats of various origin. In addition, the following nuclides are often found: sulphur-35 (half-time 87 days), chromium-51 (half-time 27 days), iron-59 (half-time 45 days) iodine-126 (half-time 13 days). By irradiation with electrons of 24 MeV and a radiation dose of 5 Mrad, as much as 100 pCi sodium-24 and 0.3 pCi6 phosphorus-33 per gram are formed in meat and meat products. (MEYER, 1966; TUCHSCHEERER et al., 1966).
The irradiation-induced molecular changes of the cell components that are discussed in this chapter certainly represent only a very small part of the disturbances that occur on the whole (ROMANI, 1966). It is easy be calculate that, under the influence of 1 Mrad of ionizing radiation, millions of ionizations, as well as chemically extremely-reactive radicals and excited conditions, are induced in each cell. As many as 1 million such ionizations occur in a single mitochondrion - that particularly indispensable particle in the cell, responsible for the energy balance and metabolism of the cell. It is furthermore estimated that after irradiation with 1 Mrad, these ionizations, radicals and excited conditions cause more than 0.5 million chemical reactions to occur in a single cell (SETLOW et al., 1962).
If foods irradiated in this manner are consumed and thus incorporated into the body, at least part of these assimilated, changed substances react in the sense of indirect radiation influence, in a manner similar to when the body is directly affected by ionizing radiation. Generally, the majority of changes thus induced in the body may be regenerated. However, it must be expected that these changes, when highly concentrated, or affecting vitally important steering molecules in the organism, or unstable and sensitive individuals and groups of individuals, may have biological effects on the individual, especially in the form of later effects. It is also possible that part of the toxic substances formed in the food during irradiation are changed, and to a varying degree detoxified, after absorption in the organism. However, satisfactory experimental proof is not yet available. In any case, remnants of questionable toxic substances remain. Certainly there is always the possibility of a detrimental effect of such substances on the extremely sensitive metabolic and cell-division processes in the gastric wall after absorption. It is stressed once again that, according to our present information, utmost care should be taken. In the next chapter, the salient point that relatively few experimental results are presently available is discussed.

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IV. EFFECTS OF IRRADIATED FOOD ON BIOLOGICAL PROCESSES
1. Cell division
If potatoes are first irradiated with only 20 - 40 krad, and then barley seedlings are cultured in the mash of these potatoes, an increase in degenerated cell nuclei occurs in the cells of the barley (SWAMINATHAN et al., 1962).
If barley and onions seeds germinate in orange and apple juice which has been irradiated with 200 krad, a remarkable increase in chromosome breaks is observed in these plants during cell division (CHOPRA et al.,1963).

The effects of extracts of irradiated plants on cell division, cause an increase in mitotic disturbances (KUZIN et al., 1961).
Cultures of human leucocytes to which an irradiated sugar solution was added show a decrease in the rate of cell division, and an increase in chromosome breaks. (SHAW et al., from WHITEHAIR, 1966).
In Tradescantia grown in a medium mixed with irradiated sugar, chromosome abnormalities which are similar to those caused by direct irradiation are found; namely fragmentations, breaks, bridges, mitotic disturbances in the entire chromosome system, including micronuclei.
If Vicia faba is reared in the same medium, the rate of abnormal cell divisions increased by 89% over the controls after 24 hours; after 48 hours, cell division stopped entirely. (HOLSTEN, 1965).
2. Mutations
If Drosophila are given food which has been irradiated with only 150 Krad, the number of sexually-bound recessive mutants, as well as the mortality of the animals, increases. Similar findings have been repeatedly confirmed. (SWAMINATHAN et al., 1963, HOLSTEN, 1965).
3. Fertility
In view of more recent radiobiological results, which reveal that direct radiation has a more drastic effect on fertility than assumed, it is not surprising that the fertility of the animals is reduced when they are fed irradiated food. Thus reproduction in rats, which were additionally fed irradiated oranges, was disturbed in some cases (PHILLIPS et al., 1961).
According to experimental results obtained in 1960, the suspicion remains that, if dogs are fed irradiated meat, this may cause a reduction in the fertility of the animals. (McCAY et al., 1960).

4. Injuries on the embryo
The most alarming gap in our information on the eventual toxic effects of consuming irradiated foods is the insufficient investigation of these effects on embryonic development. According to present information, embryonic damage is almost certain to occur. It would be irresponsible to release irradiated foods for consumption before proving beyond any doubt that they have absolutely no detrimental effect whatsoever on embryonic development.

5. Digestibility
Irradiation generally reduces the digestibility of foods. For example, when dogs were given irradiated lard with their feed, it remained longer in the stomach than non-irradiated lard, and only a minor part was absorbed (SCHREIBER et al., 1959).

6. General metabolic reactions
It is to be expected that the consumption of irradiated foods will affect the metabolic reactions in the organism. However, experimental results are sparsely available at present. Rats fed irradiated pork showed increased enzymatic activity in the liver tissue. (READ et al., 1961, TINSLAY et al., 1965).

7. Growth, vitality, mortality
A considerable number of observations on the effect of irradiated foodstuffs on growth have given rise for serious doubts. For instance, there was a significant reduction in the growth rate of the 3rd generation of rats, additionally fed oranges irradiated with only 140 krad. (PHILLIPS et al., 1961).
Similarly, the growth in rats was inhibited after feeding them freshly irradiated carrots (TINSLAY et al., 1961). A corresponding result was observed even in the fourth generation of rats fed an irradiated mixed diet with nine components. (READ et al., 1961). In addition, irradiated raisins proved to be toxic growth-inhibitors in rats. (RAICA et al., 1966). Model tests with carrot cells cultured on an artificial soil mixed with irradiated coconut milk resulted in the inhibition of cell divisions; the loss in weight of the cultures was 70% after irradiating the coconut milk with 1 Mrad, and 89% after using 2 Mrad. (HOLSTEN, 1965).
Growth inhibition, and a considerable increase in mortality resulted when soy oil was added to the feed of rats after it had been subjected to very high irradiation doses of up to 100 Mrad; 75% of the rats died within 25 weeks after test start, and within 75 weeks, 100% of the animals were dead.
The following observations, among others, were made in the test animals:
- disturbances of the digestion and enzymatic activity,
- decreased oxygen absorption,
- lowered heart frequency and body temperature,
- a 50%, and greater, loss of unsaturated fatty acids in the organism,
- protein deficiency,
- decrease in proteins and cholesterins,
- a reduction in liver activity,
- a reduction in the sensitivity of the nervous system.
If irradiated oil was injected into a fertile egg, the vitality of the hatched chicks was plainly diminished (LANG et al., 1966).
In consideration of the enormous qualitative changes in oil and simultaneous formation of explicitly toxic substances, caused by admittedly high radiation doses, the question arises as to what extent similar biological effects can be expected when applying weaker doses.
8. Hematological and immunological processes
The effects on blood formation and the blood picture after consuming irradiated food, as well as on immunological processes, have been investigated only insufficiently, or not at all. Both problematic fields are of utmost radiobiological significance. Since the after-effects on living tissue of consuming irradiated foods are similar to those of direct radiation, the relevant problems, which include an eventual reduction in resistance against infectious diseases, are of paramount importance and deserve due attention.
9. Changes of the organs
In dogs fed irradiated food, an increase in the weight of the spleen, together with congestion in this organ, was determined. (LARSON et al., 1961).
The results of other experiments, conducted mainly on dogs, lead to the conclusion that nutrition with irradiated feed frequently induces diseases of the thyroid gland. (WATSON et al., 1963 and 1965; REBER et al., 1961).
10 Carcinogenicity
As yet, it has not been possible to give a satisfactory experimental answer to the question as to what extent food irradiation could be responsible for the formation of carcinogenic substances. The relatively short-term animal tests conducted so far hardly suffice for conclusive statements on the corresponding carcinogenic effects on individuals from consuming such foods. Some authors reported a significant increase in malignant lymphomes in mice fed irradiated mixed feed. (REICA et al., 1966).

V. EXPERIENCE IN IRRADIATING VARIOUS FOOD GROUPS
1. Fruits and vegetables
The development program mainly has the following aims:
a) Irradiation-induced inhibition of ripening and sprouting processes and the prolongation of the conservation time during storage
b) Extermination or reduction of the number of microorganisms, e.g. in spices, coconut flesh, fruit juices, vegetable juices, etc., and of insects in fruits.
In many cases, the rotting processes are accelerated by irradiation. In addition to other effects, irradiation increases the porosity of cell walls, more sugar and salt are released, the rotting process of plant tissue is accelerated, whereby the microorganisms have easier access to the plant material. Furthermore, radiation effects are dependent on the degree of ripeness of the fruits and vegetables. Irradiation intensifies most of the physiologically-destructive processes induced through other means, such as heat and frost.

In order to guarantee the successful destruction of microorganisms by ionizing radiation, the application of fungus-destroying chemicals in conjunction with radiation is proposed. Furthermore, an attempt is made to make the microorganisms more sensitive to radiation by adding chemicals to the foods; thus the addition of iodine acetamide is recommended to control the fungal pests Botrytis and Rhizopus.
The destruction of microorganisms requires relatively high radiation doses, i.e. 1.5 Mrad and more. Such doses cause considerable injury to the organoleptic qualities, i.e. flavour, colour, odour and structure.
In fruit, the formation of ethylene is considerably stimulated by irradiation (MASSEY et al., 1964). Already relatively small doses (4-10 krad) will destroy or change the pectins, as well as the pertinent enzyme metabolism.
The quality of table grapes is already considerably damaged after a radiation dose of 200 - 300 krad and a week's storage. (MAXIE et al., 1964).
Prunes, irradiated with 100 - 600 krad and subsequently dried, are deprived of their aroma and flavour and become soft. (MAXIE et al.)
In irradiated peaches and apricots, the oxidation-reduction and fermentation system is sensitively injured, more alcohols and acetaldehyde are formed, the content of sugar, organic acids and propectines declines, anthocyanide increases, and the oxidation of the tannins is fortified.
In strawberries irradiated with 200 krad, manganese radicals (Mn2+) are formed, which have a considerable influence on the compatibility of such fruits. (SHAW et al., 1966).
The pectin substances and their relevant enzymes in citrus fruits (oranges, lemons, grapefruit) are already affected by 4 krad. By 25 krad, the fruits lose their green colour, become blemished and in addition, increasingly form more ethylene and gas pockets in the flesh. By 60 krad, the fruit acquires a bitter taste, and by 400 krad, vitamin C is reduced by 10-15 percent. Irradiation with I00 krad effects changes in the flavour of orange-fruit-salads. Orange juice irradiated with 800 krad suffers changes in colour and a considerable loss of vitamins. Fresh juices are particularly sensitive to radiation. In order to somewhat lessen the detrimental effects of irradiation, the addition of sugar is recommended; however, irradiated sugar itself also develops highly toxic decomposition products.
In mangos (Mangifera indiea), irradiation with 25 krad effects general spoilage. After 100 - 200 krad, the fruits blacken on the inside and outside, and the fruit flesh becomes fibrous. The vitamin C content sinks. As much as 50% of the carotinoids are already destroyed by the radicals that are formed during irradiation with medium doses. With the purpose of reducing such detrimental effects and of normalizing tissue respiration, the addition of chemicals, e.g. acetylized monoglyceride, is recommended.
Concentrated efforts regarding irradiation of fruit juices are intensively practiced in Seibersdorf (Austria).
The relatively high doses required for successful irradiation induce manifold changes in the treated juices. Valuable substances like ascorbic acid, thiamine, riboflavin are destroyed to varying degrees. In many cases, the numerous radiation-induced chemical changes cause a loss of colour and stability of the juices.
Irradiation induced products, formed mainly from the sugars of the juices, can be extremely toxic. From a biological and medical perspective, it is necessary to consider radiation sterilization in the beverage industry with great skepticism as long as these induced products have not been chemically defined, and their effects on the organism are not fully understood. This also applies to radiation treatment of the whole fruit.
Vegetables are usually affected even more drastically by irradiation in regard to their metabolism, their biochemical properties, their f!avour, colour and texture. Toxicological qualities were determined. However, thorough, systematic investigations of the entire toxicological spectrum are still lacking.
After irradiation with only 8 krad, carrots-become relatively susceptible to rotting. (SKOU, 1966).
If rats were fed irradiated carrots, their rate of growth declined and the vitamin A content in the liver was reduced.
Onions irradiated with 50 krad became glassy. When irradiated with 120 krad, their biochemistry and texture changed, and they became susceptible to fungus attacks. (STADEN, 1966).
The flavour and colour of tomatoes irradiated immediately prior to ripening changed at an irradiation dose of about 100 krad; 150 krad effected the slicing firmness; 200 krad caused hardening of the peel (ABDEL-KADER et al., 1966). The blemishes which formed on the peel were rapidly invaded by microorganisms. Biologically, the anaerobic respiration is increased in such tomatoes and more carbon dioxide than usual is released, metabolism is damaged, and the carotene content is reduced by as much as 70% and more. Simultaneously, the oxidative phosphorilation is inhibited and the amount of adenine-nucleotides decreased.

Salads are particularly sensitive to radiation. Medium doses already cause blemishing of the leaves.
Red cabbage discolours after irradiation with 100 krad.
Irradiated curled cabbage shows structural damage, and a more-or-less unappetizing colour.
Sauerkraut discolours after irradiation and develops internal gases, especially due to the hydrogen peroxide formed during radiation. (STADEN, 1966).
Feeding rats cabbage irradiated with 0.28 and 0.56 Mrad led to disturbances in the complex of enzymatic activities in their bodies, in most cases. Thereby, the content of esterases and peptidases was increased, and that of alkaline phosphatases and mono-amino oxidases reduced.
Watermelons irradiated with 50 krad had an increasing number of depressions on their peels afterwards. Cucumbers had lesions from 100 krad upwards.
Red peppers already lost in quality at 10 krad, and as little as 2 krad change the formation of the pigments. (FARKES et al., 1966).
In the USA, wheat and flour have already been released for irradiation, with the purpose of controlling pests in the stored products. Disinfestation generally requires doses ranging from 20 to 50 krad. Already with these doses, and increasingly more with higher doses, the ingredient substances are changed in numerous ways. Furthermore the baking qualities of the flour suffer changes. The increased enzyme activity, especially of the proteinases, partly destroys the proteins.
Starch and maltose are particularly sensitive to radiation. With radiation doses of 25 krad and more, starch is denatured by depolmerization9, depending on the dose and the origin of the grain. Amylopectins are formed. The viscosity is changed. Substances, precipitable by electrodialysis, occur more often. The content of starch-phosphoric acid declines. Starch decomposition products effect a non-enzymatic browning in the starch. Water extracts of flour can be flocculated without difficulty.
With higher doses, the carotinoids decrease and disappear almost entirely. Already medium irradiation doses subject the lipoids to drastic changes. The qualities of irradiated wheat and flour are additionally affected by storage. Thereby the colour of breadcrumbs baked with irradiated flour is also increasingly changed. Bread baked with flour irradiated with medium doses has a repulsive odour when taken out of the oven. (DESCHREIDER, 1966).
Surprisingly little is known about the toxic qualities of these irradiated products. In view of such fragmentary information, it is both surprising and alarming that irradiation has been released for wheat and flour. The doubts are mainly due to the occurrence of decomposition products in carbohydrates, which are very sensitive to radiation, and from other foods known to be extraordinarily toxic. At the symposium of the FAO and IAEA, held in Karlsruhe in 1966, the situation was accurately defined (by GOLUMBIC and DAVIS, 1966) as follows:
"These scattered and incomplete reports on the quality effects of irradiation on different grains reflect the paucity of information on the subject"

2. Meat and meat products, as well as sea food
Depending on the dose, the irradiation of meat effects the formation of an incalculable number of decomposition products. A considerable number of these products are volatile and additionally affect the smell of the irradiated meat. These, as well as other irradiation by-products, can change the taste of the meat to such an extent that it becomes unpalatable. Some of the decomposition products of irradiated meat are suspected to be hazardous to health if consumed. It is significant for the entire situation that hardly any investigations have been conducted in research laboratories on the effects of these decomposition products on human health. In contrast to this, scientific information on processes that impede the marketing of irradiated meat, i.e. processes having a detrimental effect on appearance, aroma, flavour, is abundant. (BATZER, BURKS, et al., 1959, KAUFFMANN 1962, MERRITT 1965, 1966, MOLL 1963, MONTY et al., 1961, MOORE et al., 1963, RHODES 1964, SCRIBNEY et al., 1955, URBAIN 1965, WICK et al., 1961).
Basically, there is no difference between the aroma and appearance of irradiated meat of different origin (pork, veal, beef, lamb). However there are differences in texture.
The ingredient substances of meat, especially the lipoids and fats, steroids, proteins and peptides, as well as lipoproteins and amino acids, were investigated more thoroughly with respect to radiation-induced changes.
The lipoids are particularly sensitive to radiation and are mainly responsible for the typical irradiation smell. Ionizing radiation has a very specific effect on the lipoids. However, this effect is in no way connected with the normal process of becoming rancid, during which carbonyl compounds are formed via the auto-oxidation of the fats. Therefore, it would be a misconception of, and a false criterium for, radiation effect, if it is evaluated according to the degree of rancidity.
The radiation effect on lipoids proceeds via lipoid molecular splitting, through the dissolution of linkages, with the subsequent formation of radicals, which together with oxygen, can form hydrogen peroxide, a major participant in the decomposition of meat. Particularly carbohydrates in homological series are formed. These include 15 different alcanes, 13 alcenes - particularly olefine compounds - and furthermore methyl ester, methyl acetate and acetone. During the radiation decomposition of lipoids, a total of over 80 different compounds have been determined up to now. Of this group, the volatile alcenes are mainly responsible for the typically repulsive irradiation odour of meat
Also typical of the radiation effect on meat is the decomposition of the steroids by the splitting off of the alcyl side chains, e.g. in cholesterin. Homologous sequences of alcanes and isoalcanes result.
The terminal groups are split off from side chains in the irradiated molecules of proteins and peptides, and cause the formation of other aromatic carbohydrates, as well as amino acids, which undergo further decomposition. In volatile compounds, products of proteins in meat were decomposed by radiation, e.g. methyl and ethyl mercaptan, dimethyl sulphide, carbonyi sulphide, benzol, toluol, methane and hydrogen sulphide, were determined (MERRITT, 1966). Under the effect of ionizing radiation, the lipoproteins release carbohydrates and sulphuric compounds like alcanes, alcenes, dimethyl sulphide and acetone. These decomposition products also contribute to the typical odour of irradiated meat.
The radiation effect on amino acid basically occurs via decarboxidation, causing the formation of considerable quantities of carbon dioxide. In the respective instances e.g. toluol and benzol are formed from phenylalanine, phenol and cresol from tyrosine. Sulphides, disulphides and methyl mercaptanes are formed from irradiated cysteine and methionine. The following were determined, amongst others: sulphur dioxide, carbony! sulphide, carbon sulphide, hydrogen sulphide, dimethyl sulphide and especially dimethyl disulphide.
One of the main reasons for the detrimental effects of irradiation on the texture of meat was found to be the increased solubility of the collagen. (BAILEY, RHODES).
The palatability of irradiated meat diminished considerably with-increased storage and is additionally affected by the storage temperature. (MOLL, 19963)
Doses of as little as 0.5 Mrad or even less, which are insufficient for the destruction of microorganisms in meat, induce such explicit decomposition symptoms in meat as to make it unacceptable on account of its odour and flavour in most cases. In order to reduce the foreign odour in irradiated meat, detrimental for marketing purposes, and to increase the effectiveness of irradiation, it was proposed to add radical interceptors to the meat, for instance ascorbates, odour absorbents (e.g. charcoal), as well as chemicals which increase the sensitivity of bacteria to radiation (e.g. sulphydyl compounds or antibiotics).
The relatively few experimental results concerning health damages after continuous consumption of irradiated meat reveal the need for utmost caution, and oblige all responsible branches of science to investigate this vital problem most thoroughly.
When, for example, rats were fed irradiated chicken for a longer period, considerable displacements in the enzymatic activities and of amino acid concentrations and haemorrhagical diathesis were determined. In addition, the damage to the normal functioning of the vitally important nucleotide-metabolism in the microsomes, following the consumption of irradiated meat, indicates a pronounced toxicity of such irradiate foods. (HILL et al., 1966).
Amongst the animal products, milk and dairy products are especially sensitive to radiation. In part, volatile compounds are formed, which change the colour and flavour of these foods after being irradiated with less than 0.1 Mrad.
Eggs also respond to irradiation with a detrimental change in the flavour, even at relatively low doses.
The sterilization of sea foods - especially fish - for which a considerable amount of Mrad is required, cannot be realized on account of the organoleptic changes in the irradiated products. The subsequent detrimental effect on the flavour and taste, depending also on the species irradiated, is so drastic that it discourages any prospect of sterilizing sea foods by irradiation. In addition, the changes in the products are dependent on the duration of storage before irradiation.
A simple pasteurization of sea foods has been attempted using irradiation with 0.3 to 0.5 Mrad, with the purpose of preventing too drastic organoleptic changes during subsequent cold storage. However, no convincing results have been presented until now. Many fish, e.g. salmon, suffer a drastic qualitative loss after irradiation with less than 0.1 Mrad. Filet of herring is impaired by irradiation with as little as 70 krad. Generally the irradiation of fish accelerates their destruction by enzymes, and humidity loss is caused by structural changes. Flavour and taste of such products, particularly the hemin pigmentation of many fish, are affected and soluble proteins denatured. Hydrolytic decomposition, as well as free
SH-groups, occur frequently. Relatively low doses intensify the oxidation of fats during subsequent storage. Proteins, lipids, carotoids, pigments, and colloids are changed. Through irradiation, Clostridium Botulinum increases its toxin formation.
In order to be more successful, the proposal is increasingly made to irradiate sea foods, especially fish, before or after treatment with chemical additives. In this respect, the following chemical compounds have been mentioned for addition to irradiated products: sodium benzoate, potassium sorbate, para-hydroxibenzoic acids, and their esters, carotenoids, sorbitol, tenox, trihydroxi-butyrophenon, thiodipropionic acid.
The addition of appropriate spices or corrective flavoring agents is intended to conceal the unfavourable taste of irradiated products.

VI. Summary on risks involved with the release and consumption of irradiated food
The irradiation of food has been increasingly advocated, particularly by technology and the economy. The technical possibilities and economic perspectives of the development of food irradiation on a large scale are promoted and thoroughly discussed. As long as the pertinent discussions and papers serve the scientific clarification of the situation, they represent part of man's efforts to expand present knowledge. However, restrictive steps to confront this development have to be taken by responsible authorities and the public, if the problem of the release of food irradiation for trading and consumption purposes is to be solved in a satisfactory way. In this case, all the aspects of this problem have to be carefully considered and should not be handled only by technology and industry, but also by biology and medicine. Man has to be the focal point in the progressing development of food irradiation. Therefore only such developments are acceptable, which are in no way harmful to man as an individual and a social and generative being.
However, our present knowledge of the effects on health after the consumption of irradiated foods is alarmingly fragmentary and entirely insufficient for a decision regarding a release of irradiation processes. Furthermore the disproportion between our present knowledge and the progress of irradiation technology is increasing.
In spite of the paucity of relevant biological and medical information, some countries have released several foods to be irradiated for trading and consumption purposes.
In the Federal Republic of Germany, the food law, in its revised version of 1964, requires a corresponding approval for the permission of food irradiation. In other European countries, similar legislation exists. In the near future, the responsible authorities of other countries will be confronted with the decisions on applications for approval of designated irradiation processes.
The Regulation of Food Irradiation of 1959, valid in the Federal Republic of Germany, permits the treatment of food with ionizing radiation not exceeding 10 rad for controlling and measuring purposes. According to this law and considering the relatively low doses permitted, this release is not included in the problem under discussion here, namely the radiation of food for the purpose of processing and preserving it for commercial use. In this, as in similar cases, the demand for conscientious investigation of the pertinent biological-medical problems remains the same. In the problems discussed, the question regarding the possible biological effects from the continuous consumption of food irradiated with low doses on particularly sensitive groups of individuals - which is similar to the problem of the effect of smaller, chronically administered direct radiation doses - would require special attention. Problems regarding the reduction of fertility or disturbance of cell processes in the intestinal epithelia should be our foremost concern.
The decisive basic demands to resolutely and systematically support research on the health hazards that accompany the consumption of irradiated food, and to bring it into an adequate relationship to the support of radiation technology, remain. This would require a more profound knowledge of changes induced in food by radiation on the one hand, and the biological, physiological and biological effects on the individual following consumption of such food on the other. Release should be withheld until the basic biological and medical problems arising from it have been satisfactorily and conclusively answered in all respects.
Consequently all considerations regarding the possible release of irradiated foods containing carbohydrates is not open to discussion at the moment because, in spite of the fact that the toxicity of irradiated products of carbohydrates has been established beyond doubt, neither its extension nor the chemism of the toxic substances is known. Above all, it is necessary to be informed of the toxic qualities of the numerous radiation decomposition products of the ingredient substances of the various foods (in meat, there are more than 100). Finally it should be explained in detail which important components are primarily destroyed by food irradiation.
In the discussion on the biological value of foods, it is necessary to discard the opinion that all treatment methods of food induce changes in its biological qualities and that irradiation is only one of other equivalent causes of qualitative changes. This assumption is not justified in light of the facts and may serve to essentially mislead the general public. On the contrary, it should be emphasized that the qualitative changes caused by irradiation are in every aspect of a specific nature and can not be compared in any way with the usual chemical changes caused by other methods of treatment, e.g. effect of heat. The effective mechanism of ionizing radiation leads to the formation of chemically particularly-reactive radicals and excited molecules through ionization, to a characteristic type and number of chemical reactions, which are not unconditionally comparable to the usual changes in stored food, but require a separate investigation. It is known that toxic substances formed in food by irradiation can have an equal or similar biological effect as a corresponding direct irradiation of the organism. Thereby it is not impossible that the simultaneous effects of both noxae are combined in the organism in a manner still unknown.
All investigations on the biological values or toxicological qualities should not only be concerned with the acute damages, but also with late injuries.

** These late injuries include damages to hereditary factors and fertility, injury to embryonic growth, including deformities, different types of cancer and leukemia, effects on the immune-mechanism and vitality, premature aging, as well as combined damages in which the detrimental effects of other noxae may be increased by the consumption of irradiated food.
Anxiety is caused by the fact that, in investigations of the biological value of food, the question of late injuries is being neglected. In the investigation of late damages, it is too often overlooked that the results of animal tests cannot necessarily be applied to human beings. (editor's added comment: most animals possess an intrinsic detoxification factor that is absent in man and primates.)
Furthermore, it is seldom taken into consideration that health hazards due to the consumption of irradiated food could be vastly different in various population groups, i.e., infants, children, adults, old people, as well as ill people or expectant mothers. When irradiate foods are evaluated, hardly any attention is paid to their contribution to the entire diet, the duration of absorption, the promotion of the detrimental effects by storage conditions, the processing of foods, the irradiation of the container, and finally to the combined effects of irradiated products with other noxae, e.g. chemical additives. In order to decrease the qualitative losses caused by various tastes and flavours formed during irradiation, to intercept the radicals, which have a high chemical reactivity, and to induce greater radiosensitivity in the microorganisms in conserves, the recommendation to apply nitrates, nitrites, antibiotics and adrenaline in the case of slaughter-animals is made with more and more emphasis. Thereby the argument presented by the promoters of food irradiation, namely that food irradiation will make the addition of chemicals, otherwise indispensable for conserving purposes, superfluous, and thus improve the purity of our nutrition, no longer has any validity.
It should be kept in mind that it is extremely difficult, if not impossible, to detect applied radiation treatment in imported foods with common laboratory means. Therefore it should be an international goal to specify the radiation dose on the labels of irradiated foods.
Furthermore the evaluation of radiation-induced artificial radioactive isotopes, which are formed in the case of irradiation with specific radiation types and energies, should be explicitly radiobiological. Since in this case, the danger to health is represented by the incorporation of radioactive materials, the biological evaluation should primarily be based on their relevancy to the elements, which is mainly responsible for their biochemical behaviour and danger. Therefore, if only the total radioactivity is specified without consideration of the element types, it is as little concerned with actual risks as a simple comparison with natural radioactive potassium-40 in food. In addition it should be remembered that through irradiated fodder, a considerable increase in the concentrations may occur, primarily by way of the food chains, , and thus also a greater burdening of the individual.
Discussions and evaluations concerning the biological risks connected with the consumption of irradiated food and with irradiation itself cannot be conducted carefully and thoroughly enough. For example, the possibility that uncertain new mutants develop during pasteurization or sterilization using energetic radiation exists. It might be expected that hereditary types of microorganisms, which are more resistant to radiation, are isolated and thus create new problems. If, for instance, Clostridium'Botilinum survives while simultaneously other types of germs are destroyed, the general rotting and gas development, normally an easily identifiable symptom for the formation of botulinus toxins, may in some cases not occur in these conserves.

Above all, the present recommendations in no way suffice for an investigation of the biological risks caused by the consumption of irradiated food. They do not, or insufficiently, consider more recent information and especially the most important later injuries in man.
Before the radiobiological and toxicological problems have been clarified convincingly, the release of food irradiation for trading and consumption purposes must not be permitted.
The final decision on this problem should not be made by those concerned with the economy and technology, but rather by those experts thoroughly familiar with the biological and medical aspects of food irradiation.

References to superscripts

1 rad: A rad is a physical unit for absorbed radiation dose, or, it is the measure for the energy absorbed by 1 gram of material irradiated with energetic rays (physically corresponding with 100 erg per gram).
1 Kilo-rad (symbol: krad) = 1000 rad
1 Mega-rad (symbol: Mrad) = 1 million rad
alcanes: saturated hydrocarbons
aleenes: unsaturated hydrocarbons (olefines)
Electron volt: The electron volt (symbol ev) is a unit used in nuclear physics denoting the energy or velocity of a particle. Physically it corresponds with the velocity gained by an electron when accelerated by an potential difference of 1 volt.
I kilo-electron volt (symbol: keV) : I000 ev
1 mega-electron volt (symbol: 1MeV) 1 million electron volt
Half-time: (half-life) The half-time of a radioactive substance is the time in which, through radio-active nuclear disintegration half of the original amount of the radioactive atoms of this substance (50%) has disintegrated. After a second half-time, only 25%, and after a third half-time only 12.5% of the original amount of radioactive atoms remain. The half-time is a characteristic quality of a radioactive type of atom, which is independent of the quantity of the substances and other factors.
Curie: The curie (symbol: ci) is a unit of radioactivity. It corresponds with 35 milliard nuclear disintegrations per second or about the radioactivity of I gram of radium.
1 milli curie (symbol: mCi) = one-thousandth curie
1 micro curie (symbol: yCi) : one-millionth curie (: 37,000 nuclear disintegrations per second)
1 pico curie (symbol: pCi) : one-thousand milliarth curie
Hematology: The branch of medicine which has to do with blood and blood diseases
Immunology: The science which has to do with immunity and the processes which lead to immunity i.e. resistance against infections
Depolymerization: A process in which large size molecules are divided into smaller ones.