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Wholesomeness of irradiated food
Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Wholesomeness of irradiated food Dieter A.E. Ehlermann 1 Brüsseler Ring 63, 76344 Eggenstein-Leopoldshafen, Germany
H I G H L I G H T S
Processing of food by ionizing radiation is safe and wholesome. Conclusion adopted by WHO and by many international and national bodies. Review of pertinent publications confirms this observation again. Several consumer groups and even a few governments fundamentally oppose food irradiation for various reasons.
art ic l e i nf o
a b s t r a c t
Article history: Received 18 April 2016 Received in revised form 7 August 2016 Accepted 16 August 2016
Just with the emergence of the idea to treat food by ionizing radiation, the concerns were voiced whether it would be safe to consume such food. Now, we look back on more than hundred years of research into the 'wholesomeness', a terminology developed during those efforts. This review will cover the many questions which had been raised, explaining the most relevant ones in some detail; it will also give place to the concerns and elucidate their scientific relevance and background. There has never been any other method of food processing studied in such depth and in such detail as food irradiation. The conclusion based on science is: Consumption of any food treated at any high dose is safe, as long as the food remains palatable. This conclusion has been adopted by WHO, also by international and national bodies. Finally, this finding has also been adopted by Codex Alimentarius in 2003, the international standard for food. However, this conclusion has not been adopted and included at its full extent in most national regulations. As the literature about wholesomeness of irradiated food is abundant, this review will use only a few, most relevant references, which will guide the reader to further reading. & 2016 Elsevier Ltd. All rights reserved.
Keywords: Food irradiation Radiation processing Ionizing radiation Wholesomeness Induced radioactivity Free radicals Toxicological safety Nutritional adequacy Feeding tests Hygienic safety Resistant microorganisms Mutation Consumer concerns
1. Introduction When ionizing radiation was first discovered, the nature of this effect remained quite strange, un-understandable, being particles as well as photons. Quite remarkable, as early as this new kind of radiation had been discovered, first proposals have been made for its exploitation.2 It turned out it was not a property of the rays,
E-mail address: [email protected] Formerly with: Federal Research Centre for Nutrition, Karlsruhe, Germany. 2 Minck, F. (1896) Zur Frage über die Einwirkung der Röntgen'schen Strahlen auf Bacterien und ihre eventuelle therapeutische Verwendbarkeit. [About the effect of X-rays (Röntgen-rays) on bacteria and their possible therapeutic exploitation]. Münchener Medicinische Wochenschrift 43 (5), 101–102. It should be noted this first ever publication contained a range of experimental errors and was superseded by a corrected version later on. 1
particles or photons, but the effect of energy transferred by their interactions. The new effect was ‘ionization’, i.e. creating charges on molecules by expelling electrons and by breaking molecular bonds; later on it was detected that also ‘free radicals’ are formed, i.e. shifting the position of electrons on molecules without creating any charge. Both kinds of effects were likewise effective in creating significant chemical changes, finally resulting also in the useful effects to be exploited. However, the nature of those effects was understood only after decades of intense research. Some research revealed quite useful applications becoming available; however, several concerns about possible negative effects could not be answered initially. This was true for treating food by ionizing radiation as well as in industrial as in therapeutic applications. The concern with food was induced radioactivity, the creation of new toxic substances and compounds, and the formation of genetic changes and more.
http://dx.doi.org/10.1016/j.radphyschem.2016.08.014 0969-806X/& 2016 Elsevier Ltd. All rights reserved.
Please cite this article as: Ehlermann, D.A.E., Wholesomeness of irradiated food. Radiat. Phys. Chem. (2016), http://dx.doi.org/10.1016/j. radphyschem.2016.08.014i
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Fig. 1. The course by time of the number of publications on the wholesomeness of food.
Note: The terminology of ‘wholesomeness’ must be recognized and understood at its full extent (from the Shorter Oxford English Dictionary): ‘whole’¼“in good condition, sound”; ‘wholesome’¼“tending to do good; beneficial, salutary”. This meaning implies not only that any deleterious or noxious effect is absent. The publications in the field of food irradiation are abundant, and the number on wholesomeness is still increasing (cf. Fig. 1); consequently, this report is more a survey, and not at all a typical academic review. For this reason, a quite different approach is chosen here, including the structure of the references. Full details for all the many effects and concerns are found elsewhere, being discussed only in the few central references given here. The reader should be guided by the two groups of references: Group A: the standard references to conclusions by international experts, as well as a very few fundamental publications; Group B: a list of a few out-standing references for positive and negative findings and aspects; examples for further reading. Footnotes are used to link specific references directly to the discussed topic. It is quite remarkable how the international scientific community joined their efforts (despite being hampered by the Iron Curtain): national research laboratories co-operated; governments created a forum IFIP (International Food Irradiation Project at Karlsruhe, Germany) to co-ordinate the research, to discuss and evaluate results obtained, to publish joint research, develop new tasks from the results obtained. These and other results were the fundament on which JECFI (FAO/IAEA/WHO Joint Expert Committee on Food Irradiation) was created to parallel the JECFA (Joint Expert Committee on Food Additives) and to determine whether irradiated food is ‘wholesome’ to consume.
2. The judgement by the international scientific community Rather late, an international co-ordination of the manifold and spread activities into research about the wholesomeness of irradiated food commenced; before this, even national co-ordination was rare. A Joint FAO/IAEA/WHO Expert Committee on Food Irradiation (JECFI) was already convened in 1963, first time. The International Project in the Field of Food Irradiation (IFIP) was founded by a number of countries in 1970, with an administrative seat at the (then) Federal Research Centre of Food Preservation, Karlsruhe Germany. A wide range of research projects was started and co-ordinated, more and more countries joined this project. The several reports by JECFI and by IFIP make evident the initial uncertainty about a possible outcome (positive or negative), the intention to avoid a diffuse approach, but the aim to achieve the goal stepwise. In 1983 the IFIP ended its activities (finally closed in 1984) for the reason that its purpose had been achieved with the final conclusion by JECFI in 1983 that any food
irradiated upto10 kGy (grand average) is save to consume. This included the conclusion that in a long term consumption of irradiated food receiving at the average 10 kGy, and receiving at up to 95% a dose up to 15 kGy, as long as the grand average of 10 kGy is observed, would be save to consume; with the consequence that the 5% remaining might receive even any dose above the 15 kGy. This makes evident that the experts did not see any particular health significance even at higher doses. This implies also that no health problems arise when some minor part of the food is irradiated even at extremely high doses. Only in 1999 a Joint FAO/IAEA/WHO Study Group on High-Dose Irradiation (JSGHDI) was convened, which concluded that even any upper dose limit was dispensable. Finally, Codex Alimentarius also adopted this position in 2003. It might also be noted that the amount of publications on wholesomeness continued to increase even drastically after the findings of the JSGHDI in 1999 (see Fig. 1). Many fundamentals and details of such research can be found in a textbook by Diehl (1995) and in two publications by WHO (1994 and, 1991). The several specific studies and publications after this textbook, and after JECFI and JSGHDI just confirm the earlier general findings and add same details, but do not put in question the fundamental conclusions. It should be noted that with the end of IFIP in 1983 the International Consultative Group on Food Irradiation (ICGFI) had been founded in 1984; it served the information exchange between its member states, in particular about further work and results about wholesomeness, but also about the world-wide regulations in radiation processing of food and about respective international trade; ICGFI was ended in 2004. The many reports from ICGFI are accessible through the Food and Environment Protection Section (FEPS) of the Joint FAO/ IAEA Division of Nuclear Techniques in Food and Agriculture, Vienna.
3. Radiation processing by irradiation in general It must be kept in mind what the purposes of processing food by ionizing radiation are and in which relation the objectives achieved must be seen with regard to possible and hypothetical risks: Low dose (up to 1 kGy) Inhibition of sprouting potato, onion, garlic, ginger root, chestnut Insect disinfestations cereals, pulses, fresh and dried fruits, Parasite disinfection fresh pork and fish Delay of ripening tropical fruits Medium dose (1– 10 kGy) Extension of shelf-life fish and seafood, strawberries, asparagus Inactivation of raw and frozen seafood, meat and spoilage poultry, and pathogenic chicken feet, raw milk cheese, life bacteria oysters Improving increased juice yield (grapes), technological reduced cooking time (dehydrated properties vegetables) High dose (above 10 kGy) Industrial sterilization meat, poultry, seafood, sausages, space food, (combination with prepared meals, hospital diets mild heat) Decontamination of spices, enzyme preparations, natural additives/ingredients gum, gel
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It must also be realized that there is - by the principle - not at all any treatment or activity which does not have at the same time some risk or unexpected side-effect. However, for food irradiation the international consensus is that the benefits by far outweigh any such theoretical risk. And for comparison: radiation processing is since long standard in our life, for example: – – – – – – – –
car tires tubes for floor-heating pipes for gas transport wires and cables (insulation) packaging materials (eg. heat-shrink foils) human implants units of stored blood medical products
Of course, we do not eat tires, but packaging materials already come quite close to our food. And in certain circumstances the irradiation of units of stored blood is the only way to suppress certain repulsive reactions in blood transfusion. And the irradiation treatment of medical products is a standard to ensure the high hygienic quality. However, this is all not seen normally by the consumer, ie. the patient; and does not create any concern.
4. Amount of publications covering wholesomeness Today, with the several literature services, it is easy to screen the several data collections; however, the unerring retrieval is hampered by the inconsistent use of keywords and of terminology. For example Fig. 1 shows the result of a specific search in SCOPUS restricted to the query term “’food irradiation’ AND (wholesomeness OR ‘nutritional value’)”: omitting ‘nutritional value’ renders a rather small number of hits. With the given query, the first publication is in 1963 with a tendency to increase until today, totally 140 entries. This is not the full truth as many papers about analytical methods to detect irradiated food on the market place also convey information about the health significance of the particular radiation specific chemical changes used, including the side-view to wholesomeness. Expanding the search term to a longer list of keywords relevant to wholesomeness results in 580 hits, renders a first hit even in 1958 and reveals a tremendous increase in recent times! For this reason it is impossible to give a full picture of relevant publications; and the reader is direct to try his skills and fortune to find the most appropriate hits for his concern and interest. It should be noted that neither after the decision by the JSGHDI in 1999 (marked in the figure by a vertical line) nor after decisions by adoption in Codex Alimentarius in 2003, the academic excitement about this topic calmed down, measured in amount of relevant publications. Instead, a significant increase of publications is observed; despite the fact that the issue appears to be finally resolved. Most of those newer publications only confirm the earlier findings, add a few details or aspects. In consequence, all those contributions need not to be discussed here in full detail. However, there have been a few out-standing observations which will be covered in some detail.
5. Aspects to judge safety of irradiated food Effects: chemical, biological, physical, ecological. Safety: radiological, toxicological, microbiological, nutritional. Paracelsus (1493–1541): “Dosis sola facit venenum” or ‘only the dose makes the poison’. In modern words: there is by the principle no ‘good’ or healthy food; it is the quantity. And it is the composition and the
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treatment which determine the final positive or negative effect. This implies in judging the safety of irradiated food to observe the balance between positive and negative effects. Irradiation as a treatment causes inevitably also negative effects. A drastic example: irradiating fruit for insect disinfection and quarantine purpose inevitably causes (very) limited vitamin losses, which are of no relevance for the health of the consumer, but the treatment protects the environment in certain areas of fruit production. Or: the immuno-compromised and the astronauts would prefer a diet radiation-sterilized for their safety, and at the same time making available food which without this treatment would not be available for them. These inherently contradictory aspects make the decision by authorities so difficult, mostly under dispute; and frequently this dilemma is outside the understanding of consumers, consumer protectors and of activists against food irradiation. The following considerations are devoted to discussing such arguments and conflicts.
6. Several specific topics It must be recognized that a range of studies and publications generated fundamental questions into the wholesomeness of irradiated food. The most significant observations will be discussed below in some detail. It has also become evident that all those concerns have finally been proven not to be relevant. 6.1. Very early studies Initially, the methodology for such studies was not well developed and many reports revealed significant deficiencies in the experimental design; also the accuracy of the analytical methods used developed only over the years. However, many of the effects observed in early studies could be attributed to other factors (‘confounders’). And from the more thorough studies it was concluded and confirmed that toxic compounds are formed, but in minute quantities of no concern for consuming irradiated food. And a majority of those compounds was already contained also in un-irradiated food, however in quite different relative amounts. There was an academic chase and competition to find ‘unique radiolytic products’; but it failed. For any ‘new’ compound finally some classical way of formation could always be confirmed. (see discussion and footnote 7 below) However, it turned out that ionizing radiation may form some of such compounds in relatively larger proportions compared to the traditional treatments, what is also used for the detection of irradiated food on the market place by the food control laboratories. 6.2. Nuclear concerns Because of the consequences of nuclear bombing of Fukushima and Nagasaki the general public became alerted about the hazards of radiation and radioactive contamination. In this context, food irradiation was understood and termed as a nuclear technology (denounced as ‘atomic food’). The science had to answer those concerns, proving that irradiated food does not become radioactive. Once the process is conducted correctly and strictly controlled there will be no induced radioactivity. USA has even lifted the upper limit for the utilization of X-rays from 5 MeV to 7.5 MeV with the reasoning that in this energy range no induced radioactivity can be observed under conditions practical for food processing. Just for comparison: in early studies in the US even electrons up to 24 MeV have been used for some experiments. The conclusion was the food indeed had accumulated considerable induced radioactivity; however because of the nature of this
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radioactivity all would have decayed within half an hour, resulting in no hazard to the employees of the facility. But and of course, such approach is not acceptable today and for commercial applications. Other concerns were that irradiation facilities would pose a risk to the environment. It was difficult to clarify to the general public that processing by ionizing radiation is not a nuclear technology, even when using radioactive cobalt-60 bread in a nuclear reactor. Of course, facilities for radiation processing in general using traditionally Co-60 would need the transport of the radioactive sources; also again about every 12 years for replenishment. Those transports have been proven to be ultimately safe; and also the operation of facilities using Co-60 has never posed any risk to the environment or the population around such facility. It must be noted that in early operations food packaging had been contaminated by Cs-137 or Co-60 from the water pool in which those sources had been stored; when the source was raised from the safe position in the pool to the irradiation position still some water dropped from the pencils and sprinkled to the goods to be irradiated. (This is no longer practice in isotope facilities! ) Furthermore, many facilities have now been established, using machinegenerated radiation as electrons and X-rays which are switched off when not used. 6.3. Free radicals Several obvious effects of ionizing radiation to the chemistry of irradiated food were quite ‘strange’ until some of it was explained by ‘free radicals’ created. These are chemical entities which have not become radioactive by irradiation, but being converted into a chemically excited and aggressive state. This implies that particular and unexpected reactions may occur once this stored energy is released. One concern was that ‘free radials’ ingested with the ordinary food would cause unhealthy effects. The life of free radicals in a humid environment is very short-lived; hence, at ingestion those free radicals just decay. (see also Renner & Reichelt in references Group B) In a dry environment free radicals are very long lived, what is used for analytical identification by the food control authorities. However, the substrates are bones and shells which are not a compound of human nutrition. In a typical human food, free radicals are contained only in an essentially negligible quantity. 6.4. Impairment of sensory and nutritional quality The JSGHDI states that any food treated at any high dose is acceptable and healthy as long as it is palatable. This statement includes and acknowledges that any food destroyed by inappropriate irradiation treatment may have lost its essential properties; but not necessarily becoming hazardous for consumption. For example, lettuce irradiated at high doses looses sensory properties, in particular its texture; consequently there is no necessity to evaluate whether it would still be innocuous to consume. Impairment of sensory quality is not at all of any relevant concern! Such food is just not consumed; the damage is exclusively with the producers. Nutritional quality is much more difficult to be judged; however, there are abundant scientific studies which have been evaluated by international and national expert bodies and authorities. It must not be neglected that from time to time observations from scientific studies are published which relate the effects observed to an impairment of nutritional quality and not to the formation of toxic compounds. The most irritating observation is the ataxy caused exclusively in Australian cats by a feed irradiated at extremely high doses (see discussion below) and not jet finally resolved.
6.5. Resistant microorganisms Whether radiation processing of food would contribute to the emergence of mutated microorganisms quite resistant to any treatment had been a highly disputed issue. Treatment of microorganisms by ionizing radiation causes mutations, no dispute! But the evidence is that those mutated microorganisms are more sensitive to the environment and less competitive to the normal micro-flora in our environment; they do not survive. The general experience had been that chemical treatments always caused an ‘escape’ (cf. MRSA). And particularly for our hospitals those ‘multiresistant’ germs became and still are of major concern. However, all reports confirm that treatment by ionizing radiation does not create such mutations or resistance. Irradiated microorganisms remain to be sensitive to the standard measures as cold or heat treatment, to treatment by classical antimicrobial food components and additives, and to repeated irradiation. 6.6. Formation of new, toxic compounds From the beginning, there was the suspicion that hitherto unknown chemicals might be built, in particular such compounds never contained ‘naturally’ in food. It was in the seventies when Kuzin introduced the terminology of ‘radiotoxins’, in order to explain effects which could not easily be explained by chemical changes in some compound.3 However, this terminology was already used-up to name radioactive substances causing toxic effects by their radioactivity, most prominent plutonium. Despite this conflict in terminology this denotation continued to be used in some publications. (SCOPUS reveals 22 publications related to ‘radiotoxin’, 12 have an author Kuzin, from 1970 to 1996, the others are not related to food). It turned out that this spectacular species of toxic compounds (in the definition by Kuzin) is just not existing. However, the search for such exotic chemical species continued and an exciting topic became URPs (Unique Radiolytic Products), i.e. chemical entities which are exclusively formed by the action of ionizing radiation. Such compounds were also of great interest for the analytical identification of (unlabelled) irradiated food on the market place. However, the final conclusion was that such compounds are not existing, but their relative contribution in a food can serve as a reliable index for irradiation. Among those compounds studied were 2-ACBs. These compounds are also present in unirradiated food, but in very low concentration4; for this reason they were initially not detected and, hence, considered URPs. The Scientific Committee on Food (SCF, today EFSA) of the EU had already concluded that the occurrence of 2-ACBs is of no concern.5 WHO has adopted the same position in 2003.6 Also furans in fruit juice caused some concerns; but also this finally turned out to be of no practical significance. 3 Kuzin, A.M., Yurov, S.S., Vasiloi, S.E., Radiotoxins of E. coli B (in Russian), Radiobiologiya, Volume 13, Issue 5, 1973, Pages 691–694 Kopylov, V.A., Osipova, I.N., Kuzin, A.M., Biologically active substances formed in γ irradiated potato tubers and their action on sex cells of mammals (in Russian), Radiobiologiya Volume 14, Issue 4, 1974, Pages 559–563. 4 Prasad S. Variyar, Suchandra Chatterjee, M. G. Sajilata and Arun Sharma, (2008), Natural Existence of 2-Alkylcyclobutanones, J. Agric. Food Chem., 2008, 56 (24), pp 11,817–11823. 5 Statement of the Scientific Committee on Food on a report on 2-alkylcyclobutanones (expressed on 3 July 2002); European Commission; http://ec.europa.eu/ food/fs/sc/scf/out135_en.pdf (last visited ..). 6 WHO Statement on 2-Dodecylcyclobutanone and Related Compounds, March 2003 WHO DCB Position UpdateFinal Rev2.doc No URL available, copy available on demand from this author.
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6.7. Polyploidy in malnourished children A rather strange experiment from India caused much irritation for the scientific community: malnourished children in a hospital for rehabilitation were given a diet containing irradiated wheat.7 How could any responsible scientist repeat this experiment in order to confirm the results? How to get enough malnourished (volunteer? ) children for such experiment? The Indian study had only 20 children in four groups, one of which received the irradiated wheat. The composition of the diet was never reported. The slides for counting polyploidy were never available for independent counting. And because of the small number of children any statistical evaluation was impossible. There were also m ore deficiencies in the experimental set-up. (See a detailed discussion by Diehl, 1995, p,198 ff.) But the huge scientific and political excitation began about 20 years later when the historic publications were used by ideological opponents aggressively to condemn food irradiation in general.8 Polyploidy is quite natural and frequent in nature; instead of the standard set of duplicate chromosomes a larger number is observed; there are even species which have regularly more than duplicate sets. Consequently, the significance of this effect in humans is unknown; still, this sporadic occurrence is not considered a negative sign for health. It might be noted that polyploidy in plant breading may result in increased yield. 6.8. Ataxy in Australian cats In 2008 a cat food incident occurred in Australia9: cats receiving a certain brand of cat food were paralysed; this caused considerable concern in the public. The incident was isolated to only one importer of cat food which had been irradiated. There have been no past or later incidents with irradiated pet food in Australia. The importation of some products to Australia is, by law, subject to certain quarantine provisions. From the options given to the importer, gamma irradiation was chosen as their preferred process. The importer chose not to run trial product prior to importing commercial volumes. The requirement for the Orijen cat food was set at a minimum dose of 50 kGy. When incidents of cats becoming ill were highlighted, an investigation into the cause was conducted. No conclusive evidence has been attributed to gamma irradiation as being the root cause, nor indeed has evidence been 100% attributed to the effects of gamma irradiation on the food. As 7 Bhaskaram, C., Sadasivan, G. (1975), Effects of feeding irradiated wheat to malnourished children, American Journal of Clinical Nutrition Volume 28, Issue 2, Pages 130–135. 8 Vijayalaxmi, (1999), Comparison of studies on the wholesomeness of irradiated wheat: A review, Nutrition Research 19, Issue 7, 1113–1120. Vijayalaxmi and Srikantia, S.G., (1989), A review of the studies on the wholesomeness of irradiated wheat, conducted at the national institute of nutrition, India, International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry, Volume 34, Issue 6, Pages 941–952. 9 Orijen Cat Food | Australia, updated Nov.26, 2008. http://www.championpetfoods.com/wpcontent/uploads/2015/01/Australia_Consumer_Release.pdf. Cassidy, J.P., Caulfield, C.D., Jones, B.R., Worral, S., Condon, L., Palmer, A.C., Kelly, J., (2007), Leukoencephalomyelopathy in Specific Pathogen-free cats, Vet. Pathol. 44, pp.912–916. Caulfield, C.D., Cassidy, J.P., Kelly, J.P. (2008), Effects of gamma irradiation and pasteurization on the nutritive composition of commercially available animal diets, J. Am. Assoc. Lab. Animal Sci. 47(6), pp.61–66 G Child, DJ Foster, BJ Fougere, JM Milan and M Rozmanec, (2009), Ataxia and paralysis in cats in Australia associated with exposure to an imported gamma-irradiated commercial dry pet food, Australian Veterinary Journal Volume 87, No 9, September 2009. pp 349–351. http://foodlabellingreview.gov.au/internet/foodlabelling/submissions.nsf/lookupSubmissionAttachments/1WCME-85CSN920100512070110ABQI/$FILE/205a. pdf.
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a result of this incident, the use of gamma irradiation as an approved treatment on cat food was suspended. The importers were instructed to label all imported pet food (dog food) that underwent gamma irradiation processing with “must not be fed to cats”. To date, it has not been revealed what the toxic factor in the cat issue might have been. Not vitamin or nutrient depletion; not 'activation' of some strange minor component. The publication by Caulfield et al., 2008, holds 10 citations; none clearly revealing the issue. 6.9. Consumer concerns From the beginning several consumer organizations voiced concerns whether it would be ‘safe’ to consume irradiated food, at all. And a number of observations (see discussions above) were strong indications of unresolved issues. However, in now more than 100 years of research the questions raised are resolved and the consumers accept irradiated food where it has become available together with an understandable explanation of the new technology. This situation is not recognized by most consumer activists. Some consumer organizations have decided to continue their protests: namely the International Organisation of Consumer Unions (IOCU, today Consumer International), as well as Public Citizen and others; more details to be found on their WEBsites. The activities by IOCU in 1988 are most representative for this issue and discussed here to some extent.10 As participant to this international conference at Geneva, 1988, IOCU had failed to submit a manuscript; consequently, no presentation on their consumer issues and concerns was on the programme. In the contrary, a scientific presentation had been accepted, but IOCU complained this would not be their position and did not report to the meeting. Instead and against all rules of conduct, IOCU distributed their ‘Open Questions’ to the participants. The organizers even tolerated this and provided in the evening, outside the conference programme, for a presentation by IOCU with a response by recognized experts. These ‘answers’ refuted point by point the allegations raised by IOCU: But again, IOCU proved to be not open to factual and scientific discussion, instead they distributed another pamphlet. This situation is narrated here to a limited extend; it reveals the difficulty for scientists to make their results understandable also to opponents of their intentions.
7. Conclusions Any food processed by ionizing radiation up to any high dose is safe to consume, as long as it is palatable. In this aspect, irradiation is not different to other techniques; compare: the barbecue burned to coal! From time to time some unexpected effects are discovered which appear to shed light on hitherto undetected risks of food irradiation. But a thorough scientific evaluation reveals regularly that the observed effect is extremely small or just not relevant under practical circumstances. For example, 2-ACBs are potentially carcinogenic, but this is irrelevant under practical circumstances; on the other hand it serves for the reliable detection of unlabelled 10 Outstanding questions on the safety of irradiated food, IOCU (undated, 1988). Comments on IOCU's paper “Outstanding questions on the safety of irradiated food“, prepared by Professors Cliver, Diehl, Hawthorne and Kampelmacher, Temporary Advisors to the FAO/WHO/IAEA/ITC International Conference on Acceptance, Control of, and Trade in Irradiated Food, Geneva, Switzerland, 12 – 16 December 1988. IOCU press release (undated, 1988)Unfortunately, there are no publications available on this issue; however, this author (being a participant of this conference) holds a range of copies which are available upon request.
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irradiated food (fat containing). Ionizing radiation is difficult to understand by the ordinary consumer; and some consumer activists use this to manipulate the public perception. In the contrary, the scientific community is firmly convinced that irradiated food is safe to consume. The safety and wholesomeness of irradiated food has been re-confirmed again and again; national and international authorities have underlined this. Despite this the practical exploitation of radiation processing of food is still scarce; many governments are very reluctant to permit irradiated food on the market place; and also the food industry is not at all bringing the irradiated food to the market with confidence in consumer acceptance.
References References group A Codex, Alimentarius, 2003. General Standard for Irradiated Foods. Diehl, J.F., 1995. Safety of Irradiated Foods. Marcel Dekker, New York, 2nd edition. JECFI, 1963. Wholesomeness of irradiated food. FAO, Rome. WHO, 1994. Safety and Nutritional Adequacy of Irradiated Food. WHO, Geneva. WHO, 1991. Food Irradiation, A Technique for Preserving and Improving the Safety of Food. WHO, Geneva (revised edition of 1988).
References group B Renner, H.W., Reichelt, D., 1973. On the wholesomeness of high concentrations of free radicals in irradiated foods. V20. Zentralblatt fur Veterinarmedizin - Reihe B, pp. 648–660.
Further reading JCGHDI, 1999. High-dose irradiation: wholesomeness of food irradiated with doses above 10 kGy. Technical Reports Series 890. WHO, Geneva. JECFI, 1977. Wholesomeness of irradiated food. Technical Report Series no. 604. WHO, Geneva. JECFI, 1981. Wholesomeness of irradiated food. Technical Report Series 659. WHO, Geneva. JECFI, 1970. Wholesomeness of irradiated food with special reference to wheat, potatoes and onions. Technical Report Series no. 451. WHO, Geneva. JECFI, 1966. The technical basis for legislation on irradiated food. Technical Report Series no. 316. WHO, Geneva. Diehl, J.F., 1979. Food irradiation. Radiation Physics and Chemistry. Vol. 14(1–2), pp. 117–125. Diehl, J.F., Scherz, H., 1975. Estimation of radiolytic products as a basis for evaluating the wholesomeness of irradiated foods. Int. J. Appl. Radiat. Isot. 26 (9), 499–507. Ehlermann, D.A.E., 2014. Safety of food and beverages: safety of irradiated foods. In: Motarjemi, J. (Ed.), Encyclopedia of Food Safety, Vol. 3. Foods, Materials, Technologies and Risks 3. Academic Press, Elsevier, New York, pp. 447–452. Elias, P.S., 1980. The wholesomeness of irradiated food. Ecotoxicol. Environ. Saf. 4 (2), 172–183. Farkas, J., Mohácsi-Farkas, Csilla, 2011. History and future of food irradiation. Trends Food Sci. Technol. 22 (2–3), 121–126. Farkas, J., Ehlermann, D.A.E., Mohácsi-Farkas, Cs, 2014. Food technologies: food irradiation. In: Motarjemi, Y. (Ed.), Encyclopedia of Food Safety, Vol. 3. Foods, Materials, Technologies and Risks 3. Academic Press, Elsevier, New York, pp. 178–186. Hickman, J.R., 1959. Some notes on wholesomeness trials at Wantage. Int. J. Appl. Radiat. Isot. 6 (C), 258–260. Käferstein, F.K., Moy, G.G., 1993. Public health aspects of food irradiation. J. Public Health Policy 14 (2), 149–163. Reber, E.F., Raheja, K., Davis, D., 1966. Wholesomeness of irradiated foods. An annotated bibliography. Fed. Proc. 25 (5), 1529–1579. Swallow, A.J., 1991. Wholesomeness and safety of irradiated foods. Advances in Experimental Medicine and Biology. Vol. 289, pp. 11–31.
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Wholesomeness of irradiated food Dieter A.E. Ehlermann 1 Brüsseler Ring 63, 76344 Eggenstein-Leopoldshafen, Germany
H I G H L I G H T S
Processing of food by ionizing radiation is safe and wholesome. Conclusion adopted by WHO and by many international and national bodies. Review of pertinent publications confirms this observation again. Several consumer groups and even a few governments fundamentally oppose food irradiation for various reasons.
art ic l e i nf o
a b s t r a c t
Article history: Received 18 April 2016 Received in revised form 7 August 2016 Accepted 16 August 2016
Just with the emergence of the idea to treat food by ionizing radiation, the concerns were voiced whether it would be safe to consume such food. Now, we look back on more than hundred years of research into the 'wholesomeness', a terminology developed during those efforts. This review will cover the many questions which had been raised, explaining the most relevant ones in some detail; it will also give place to the concerns and elucidate their scientific relevance and background. There has never been any other method of food processing studied in such depth and in such detail as food irradiation. The conclusion based on science is: Consumption of any food treated at any high dose is safe, as long as the food remains palatable. This conclusion has been adopted by WHO, also by international and national bodies. Finally, this finding has also been adopted by Codex Alimentarius in 2003, the international standard for food. However, this conclusion has not been adopted and included at its full extent in most national regulations. As the literature about wholesomeness of irradiated food is abundant, this review will use only a few, most relevant references, which will guide the reader to further reading. & 2016 Elsevier Ltd. All rights reserved.
Keywords: Food irradiation Radiation processing Ionizing radiation Wholesomeness Induced radioactivity Free radicals Toxicological safety Nutritional adequacy Feeding tests Hygienic safety Resistant microorganisms Mutation Consumer concerns
1. Introduction When ionizing radiation was first discovered, the nature of this effect remained quite strange, un-understandable, being particles as well as photons. Quite remarkable, as early as this new kind of radiation had been discovered, first proposals have been made for its exploitation.2 It turned out it was not a property of the rays,
E-mail address: [email protected] Formerly with: Federal Research Centre for Nutrition, Karlsruhe, Germany. 2 Minck, F. (1896) Zur Frage über die Einwirkung der Röntgen'schen Strahlen auf Bacterien und ihre eventuelle therapeutische Verwendbarkeit. [About the effect of X-rays (Röntgen-rays) on bacteria and their possible therapeutic exploitation]. Münchener Medicinische Wochenschrift 43 (5), 101–102. It should be noted this first ever publication contained a range of experimental errors and was superseded by a corrected version later on. 1
particles or photons, but the effect of energy transferred by their interactions. The new effect was ‘ionization’, i.e. creating charges on molecules by expelling electrons and by breaking molecular bonds; later on it was detected that also ‘free radicals’ are formed, i.e. shifting the position of electrons on molecules without creating any charge. Both kinds of effects were likewise effective in creating significant chemical changes, finally resulting also in the useful effects to be exploited. However, the nature of those effects was understood only after decades of intense research. Some research revealed quite useful applications becoming available; however, several concerns about possible negative effects could not be answered initially. This was true for treating food by ionizing radiation as well as in industrial as in therapeutic applications. The concern with food was induced radioactivity, the creation of new toxic substances and compounds, and the formation of genetic changes and more.
http://dx.doi.org/10.1016/j.radphyschem.2016.08.014 0969-806X/& 2016 Elsevier Ltd. All rights reserved.
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Fig. 1. The course by time of the number of publications on the wholesomeness of food.
Note: The terminology of ‘wholesomeness’ must be recognized and understood at its full extent (from the Shorter Oxford English Dictionary): ‘whole’¼“in good condition, sound”; ‘wholesome’¼“tending to do good; beneficial, salutary”. This meaning implies not only that any deleterious or noxious effect is absent. The publications in the field of food irradiation are abundant, and the number on wholesomeness is still increasing (cf. Fig. 1); consequently, this report is more a survey, and not at all a typical academic review. For this reason, a quite different approach is chosen here, including the structure of the references. Full details for all the many effects and concerns are found elsewhere, being discussed only in the few central references given here. The reader should be guided by the two groups of references: Group A: the standard references to conclusions by international experts, as well as a very few fundamental publications; Group B: a list of a few out-standing references for positive and negative findings and aspects; examples for further reading. Footnotes are used to link specific references directly to the discussed topic. It is quite remarkable how the international scientific community joined their efforts (despite being hampered by the Iron Curtain): national research laboratories co-operated; governments created a forum IFIP (International Food Irradiation Project at Karlsruhe, Germany) to co-ordinate the research, to discuss and evaluate results obtained, to publish joint research, develop new tasks from the results obtained. These and other results were the fundament on which JECFI (FAO/IAEA/WHO Joint Expert Committee on Food Irradiation) was created to parallel the JECFA (Joint Expert Committee on Food Additives) and to determine whether irradiated food is ‘wholesome’ to consume.
2. The judgement by the international scientific community Rather late, an international co-ordination of the manifold and spread activities into research about the wholesomeness of irradiated food commenced; before this, even national co-ordination was rare. A Joint FAO/IAEA/WHO Expert Committee on Food Irradiation (JECFI) was already convened in 1963, first time. The International Project in the Field of Food Irradiation (IFIP) was founded by a number of countries in 1970, with an administrative seat at the (then) Federal Research Centre of Food Preservation, Karlsruhe Germany. A wide range of research projects was started and co-ordinated, more and more countries joined this project. The several reports by JECFI and by IFIP make evident the initial uncertainty about a possible outcome (positive or negative), the intention to avoid a diffuse approach, but the aim to achieve the goal stepwise. In 1983 the IFIP ended its activities (finally closed in 1984) for the reason that its purpose had been achieved with the final conclusion by JECFI in 1983 that any food
irradiated upto10 kGy (grand average) is save to consume. This included the conclusion that in a long term consumption of irradiated food receiving at the average 10 kGy, and receiving at up to 95% a dose up to 15 kGy, as long as the grand average of 10 kGy is observed, would be save to consume; with the consequence that the 5% remaining might receive even any dose above the 15 kGy. This makes evident that the experts did not see any particular health significance even at higher doses. This implies also that no health problems arise when some minor part of the food is irradiated even at extremely high doses. Only in 1999 a Joint FAO/IAEA/WHO Study Group on High-Dose Irradiation (JSGHDI) was convened, which concluded that even any upper dose limit was dispensable. Finally, Codex Alimentarius also adopted this position in 2003. It might also be noted that the amount of publications on wholesomeness continued to increase even drastically after the findings of the JSGHDI in 1999 (see Fig. 1). Many fundamentals and details of such research can be found in a textbook by Diehl (1995) and in two publications by WHO (1994 and, 1991). The several specific studies and publications after this textbook, and after JECFI and JSGHDI just confirm the earlier general findings and add same details, but do not put in question the fundamental conclusions. It should be noted that with the end of IFIP in 1983 the International Consultative Group on Food Irradiation (ICGFI) had been founded in 1984; it served the information exchange between its member states, in particular about further work and results about wholesomeness, but also about the world-wide regulations in radiation processing of food and about respective international trade; ICGFI was ended in 2004. The many reports from ICGFI are accessible through the Food and Environment Protection Section (FEPS) of the Joint FAO/ IAEA Division of Nuclear Techniques in Food and Agriculture, Vienna.
3. Radiation processing by irradiation in general It must be kept in mind what the purposes of processing food by ionizing radiation are and in which relation the objectives achieved must be seen with regard to possible and hypothetical risks: Low dose (up to 1 kGy) Inhibition of sprouting potato, onion, garlic, ginger root, chestnut Insect disinfestations cereals, pulses, fresh and dried fruits, Parasite disinfection fresh pork and fish Delay of ripening tropical fruits Medium dose (1– 10 kGy) Extension of shelf-life fish and seafood, strawberries, asparagus Inactivation of raw and frozen seafood, meat and spoilage poultry, and pathogenic chicken feet, raw milk cheese, life bacteria oysters Improving increased juice yield (grapes), technological reduced cooking time (dehydrated properties vegetables) High dose (above 10 kGy) Industrial sterilization meat, poultry, seafood, sausages, space food, (combination with prepared meals, hospital diets mild heat) Decontamination of spices, enzyme preparations, natural additives/ingredients gum, gel
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It must also be realized that there is - by the principle - not at all any treatment or activity which does not have at the same time some risk or unexpected side-effect. However, for food irradiation the international consensus is that the benefits by far outweigh any such theoretical risk. And for comparison: radiation processing is since long standard in our life, for example: – – – – – – – –
car tires tubes for floor-heating pipes for gas transport wires and cables (insulation) packaging materials (eg. heat-shrink foils) human implants units of stored blood medical products
Of course, we do not eat tires, but packaging materials already come quite close to our food. And in certain circumstances the irradiation of units of stored blood is the only way to suppress certain repulsive reactions in blood transfusion. And the irradiation treatment of medical products is a standard to ensure the high hygienic quality. However, this is all not seen normally by the consumer, ie. the patient; and does not create any concern.
4. Amount of publications covering wholesomeness Today, with the several literature services, it is easy to screen the several data collections; however, the unerring retrieval is hampered by the inconsistent use of keywords and of terminology. For example Fig. 1 shows the result of a specific search in SCOPUS restricted to the query term “’food irradiation’ AND (wholesomeness OR ‘nutritional value’)”: omitting ‘nutritional value’ renders a rather small number of hits. With the given query, the first publication is in 1963 with a tendency to increase until today, totally 140 entries. This is not the full truth as many papers about analytical methods to detect irradiated food on the market place also convey information about the health significance of the particular radiation specific chemical changes used, including the side-view to wholesomeness. Expanding the search term to a longer list of keywords relevant to wholesomeness results in 580 hits, renders a first hit even in 1958 and reveals a tremendous increase in recent times! For this reason it is impossible to give a full picture of relevant publications; and the reader is direct to try his skills and fortune to find the most appropriate hits for his concern and interest. It should be noted that neither after the decision by the JSGHDI in 1999 (marked in the figure by a vertical line) nor after decisions by adoption in Codex Alimentarius in 2003, the academic excitement about this topic calmed down, measured in amount of relevant publications. Instead, a significant increase of publications is observed; despite the fact that the issue appears to be finally resolved. Most of those newer publications only confirm the earlier findings, add a few details or aspects. In consequence, all those contributions need not to be discussed here in full detail. However, there have been a few out-standing observations which will be covered in some detail.
5. Aspects to judge safety of irradiated food Effects: chemical, biological, physical, ecological. Safety: radiological, toxicological, microbiological, nutritional. Paracelsus (1493–1541): “Dosis sola facit venenum” or ‘only the dose makes the poison’. In modern words: there is by the principle no ‘good’ or healthy food; it is the quantity. And it is the composition and the
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treatment which determine the final positive or negative effect. This implies in judging the safety of irradiated food to observe the balance between positive and negative effects. Irradiation as a treatment causes inevitably also negative effects. A drastic example: irradiating fruit for insect disinfection and quarantine purpose inevitably causes (very) limited vitamin losses, which are of no relevance for the health of the consumer, but the treatment protects the environment in certain areas of fruit production. Or: the immuno-compromised and the astronauts would prefer a diet radiation-sterilized for their safety, and at the same time making available food which without this treatment would not be available for them. These inherently contradictory aspects make the decision by authorities so difficult, mostly under dispute; and frequently this dilemma is outside the understanding of consumers, consumer protectors and of activists against food irradiation. The following considerations are devoted to discussing such arguments and conflicts.
6. Several specific topics It must be recognized that a range of studies and publications generated fundamental questions into the wholesomeness of irradiated food. The most significant observations will be discussed below in some detail. It has also become evident that all those concerns have finally been proven not to be relevant. 6.1. Very early studies Initially, the methodology for such studies was not well developed and many reports revealed significant deficiencies in the experimental design; also the accuracy of the analytical methods used developed only over the years. However, many of the effects observed in early studies could be attributed to other factors (‘confounders’). And from the more thorough studies it was concluded and confirmed that toxic compounds are formed, but in minute quantities of no concern for consuming irradiated food. And a majority of those compounds was already contained also in un-irradiated food, however in quite different relative amounts. There was an academic chase and competition to find ‘unique radiolytic products’; but it failed. For any ‘new’ compound finally some classical way of formation could always be confirmed. (see discussion and footnote 7 below) However, it turned out that ionizing radiation may form some of such compounds in relatively larger proportions compared to the traditional treatments, what is also used for the detection of irradiated food on the market place by the food control laboratories. 6.2. Nuclear concerns Because of the consequences of nuclear bombing of Fukushima and Nagasaki the general public became alerted about the hazards of radiation and radioactive contamination. In this context, food irradiation was understood and termed as a nuclear technology (denounced as ‘atomic food’). The science had to answer those concerns, proving that irradiated food does not become radioactive. Once the process is conducted correctly and strictly controlled there will be no induced radioactivity. USA has even lifted the upper limit for the utilization of X-rays from 5 MeV to 7.5 MeV with the reasoning that in this energy range no induced radioactivity can be observed under conditions practical for food processing. Just for comparison: in early studies in the US even electrons up to 24 MeV have been used for some experiments. The conclusion was the food indeed had accumulated considerable induced radioactivity; however because of the nature of this
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radioactivity all would have decayed within half an hour, resulting in no hazard to the employees of the facility. But and of course, such approach is not acceptable today and for commercial applications. Other concerns were that irradiation facilities would pose a risk to the environment. It was difficult to clarify to the general public that processing by ionizing radiation is not a nuclear technology, even when using radioactive cobalt-60 bread in a nuclear reactor. Of course, facilities for radiation processing in general using traditionally Co-60 would need the transport of the radioactive sources; also again about every 12 years for replenishment. Those transports have been proven to be ultimately safe; and also the operation of facilities using Co-60 has never posed any risk to the environment or the population around such facility. It must be noted that in early operations food packaging had been contaminated by Cs-137 or Co-60 from the water pool in which those sources had been stored; when the source was raised from the safe position in the pool to the irradiation position still some water dropped from the pencils and sprinkled to the goods to be irradiated. (This is no longer practice in isotope facilities! ) Furthermore, many facilities have now been established, using machinegenerated radiation as electrons and X-rays which are switched off when not used. 6.3. Free radicals Several obvious effects of ionizing radiation to the chemistry of irradiated food were quite ‘strange’ until some of it was explained by ‘free radicals’ created. These are chemical entities which have not become radioactive by irradiation, but being converted into a chemically excited and aggressive state. This implies that particular and unexpected reactions may occur once this stored energy is released. One concern was that ‘free radials’ ingested with the ordinary food would cause unhealthy effects. The life of free radicals in a humid environment is very short-lived; hence, at ingestion those free radicals just decay. (see also Renner & Reichelt in references Group B) In a dry environment free radicals are very long lived, what is used for analytical identification by the food control authorities. However, the substrates are bones and shells which are not a compound of human nutrition. In a typical human food, free radicals are contained only in an essentially negligible quantity. 6.4. Impairment of sensory and nutritional quality The JSGHDI states that any food treated at any high dose is acceptable and healthy as long as it is palatable. This statement includes and acknowledges that any food destroyed by inappropriate irradiation treatment may have lost its essential properties; but not necessarily becoming hazardous for consumption. For example, lettuce irradiated at high doses looses sensory properties, in particular its texture; consequently there is no necessity to evaluate whether it would still be innocuous to consume. Impairment of sensory quality is not at all of any relevant concern! Such food is just not consumed; the damage is exclusively with the producers. Nutritional quality is much more difficult to be judged; however, there are abundant scientific studies which have been evaluated by international and national expert bodies and authorities. It must not be neglected that from time to time observations from scientific studies are published which relate the effects observed to an impairment of nutritional quality and not to the formation of toxic compounds. The most irritating observation is the ataxy caused exclusively in Australian cats by a feed irradiated at extremely high doses (see discussion below) and not jet finally resolved.
6.5. Resistant microorganisms Whether radiation processing of food would contribute to the emergence of mutated microorganisms quite resistant to any treatment had been a highly disputed issue. Treatment of microorganisms by ionizing radiation causes mutations, no dispute! But the evidence is that those mutated microorganisms are more sensitive to the environment and less competitive to the normal micro-flora in our environment; they do not survive. The general experience had been that chemical treatments always caused an ‘escape’ (cf. MRSA). And particularly for our hospitals those ‘multiresistant’ germs became and still are of major concern. However, all reports confirm that treatment by ionizing radiation does not create such mutations or resistance. Irradiated microorganisms remain to be sensitive to the standard measures as cold or heat treatment, to treatment by classical antimicrobial food components and additives, and to repeated irradiation. 6.6. Formation of new, toxic compounds From the beginning, there was the suspicion that hitherto unknown chemicals might be built, in particular such compounds never contained ‘naturally’ in food. It was in the seventies when Kuzin introduced the terminology of ‘radiotoxins’, in order to explain effects which could not easily be explained by chemical changes in some compound.3 However, this terminology was already used-up to name radioactive substances causing toxic effects by their radioactivity, most prominent plutonium. Despite this conflict in terminology this denotation continued to be used in some publications. (SCOPUS reveals 22 publications related to ‘radiotoxin’, 12 have an author Kuzin, from 1970 to 1996, the others are not related to food). It turned out that this spectacular species of toxic compounds (in the definition by Kuzin) is just not existing. However, the search for such exotic chemical species continued and an exciting topic became URPs (Unique Radiolytic Products), i.e. chemical entities which are exclusively formed by the action of ionizing radiation. Such compounds were also of great interest for the analytical identification of (unlabelled) irradiated food on the market place. However, the final conclusion was that such compounds are not existing, but their relative contribution in a food can serve as a reliable index for irradiation. Among those compounds studied were 2-ACBs. These compounds are also present in unirradiated food, but in very low concentration4; for this reason they were initially not detected and, hence, considered URPs. The Scientific Committee on Food (SCF, today EFSA) of the EU had already concluded that the occurrence of 2-ACBs is of no concern.5 WHO has adopted the same position in 2003.6 Also furans in fruit juice caused some concerns; but also this finally turned out to be of no practical significance. 3 Kuzin, A.M., Yurov, S.S., Vasiloi, S.E., Radiotoxins of E. coli B (in Russian), Radiobiologiya, Volume 13, Issue 5, 1973, Pages 691–694 Kopylov, V.A., Osipova, I.N., Kuzin, A.M., Biologically active substances formed in γ irradiated potato tubers and their action on sex cells of mammals (in Russian), Radiobiologiya Volume 14, Issue 4, 1974, Pages 559–563. 4 Prasad S. Variyar, Suchandra Chatterjee, M. G. Sajilata and Arun Sharma, (2008), Natural Existence of 2-Alkylcyclobutanones, J. Agric. Food Chem., 2008, 56 (24), pp 11,817–11823. 5 Statement of the Scientific Committee on Food on a report on 2-alkylcyclobutanones (expressed on 3 July 2002); European Commission; http://ec.europa.eu/ food/fs/sc/scf/out135_en.pdf (last visited ..). 6 WHO Statement on 2-Dodecylcyclobutanone and Related Compounds, March 2003 WHO DCB Position UpdateFinal Rev2.doc No URL available, copy available on demand from this author.
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6.7. Polyploidy in malnourished children A rather strange experiment from India caused much irritation for the scientific community: malnourished children in a hospital for rehabilitation were given a diet containing irradiated wheat.7 How could any responsible scientist repeat this experiment in order to confirm the results? How to get enough malnourished (volunteer? ) children for such experiment? The Indian study had only 20 children in four groups, one of which received the irradiated wheat. The composition of the diet was never reported. The slides for counting polyploidy were never available for independent counting. And because of the small number of children any statistical evaluation was impossible. There were also m ore deficiencies in the experimental set-up. (See a detailed discussion by Diehl, 1995, p,198 ff.) But the huge scientific and political excitation began about 20 years later when the historic publications were used by ideological opponents aggressively to condemn food irradiation in general.8 Polyploidy is quite natural and frequent in nature; instead of the standard set of duplicate chromosomes a larger number is observed; there are even species which have regularly more than duplicate sets. Consequently, the significance of this effect in humans is unknown; still, this sporadic occurrence is not considered a negative sign for health. It might be noted that polyploidy in plant breading may result in increased yield. 6.8. Ataxy in Australian cats In 2008 a cat food incident occurred in Australia9: cats receiving a certain brand of cat food were paralysed; this caused considerable concern in the public. The incident was isolated to only one importer of cat food which had been irradiated. There have been no past or later incidents with irradiated pet food in Australia. The importation of some products to Australia is, by law, subject to certain quarantine provisions. From the options given to the importer, gamma irradiation was chosen as their preferred process. The importer chose not to run trial product prior to importing commercial volumes. The requirement for the Orijen cat food was set at a minimum dose of 50 kGy. When incidents of cats becoming ill were highlighted, an investigation into the cause was conducted. No conclusive evidence has been attributed to gamma irradiation as being the root cause, nor indeed has evidence been 100% attributed to the effects of gamma irradiation on the food. As 7 Bhaskaram, C., Sadasivan, G. (1975), Effects of feeding irradiated wheat to malnourished children, American Journal of Clinical Nutrition Volume 28, Issue 2, Pages 130–135. 8 Vijayalaxmi, (1999), Comparison of studies on the wholesomeness of irradiated wheat: A review, Nutrition Research 19, Issue 7, 1113–1120. Vijayalaxmi and Srikantia, S.G., (1989), A review of the studies on the wholesomeness of irradiated wheat, conducted at the national institute of nutrition, India, International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry, Volume 34, Issue 6, Pages 941–952. 9 Orijen Cat Food | Australia, updated Nov.26, 2008. http://www.championpetfoods.com/wpcontent/uploads/2015/01/Australia_Consumer_Release.pdf. Cassidy, J.P., Caulfield, C.D., Jones, B.R., Worral, S., Condon, L., Palmer, A.C., Kelly, J., (2007), Leukoencephalomyelopathy in Specific Pathogen-free cats, Vet. Pathol. 44, pp.912–916. Caulfield, C.D., Cassidy, J.P., Kelly, J.P. (2008), Effects of gamma irradiation and pasteurization on the nutritive composition of commercially available animal diets, J. Am. Assoc. Lab. Animal Sci. 47(6), pp.61–66 G Child, DJ Foster, BJ Fougere, JM Milan and M Rozmanec, (2009), Ataxia and paralysis in cats in Australia associated with exposure to an imported gamma-irradiated commercial dry pet food, Australian Veterinary Journal Volume 87, No 9, September 2009. pp 349–351. http://foodlabellingreview.gov.au/internet/foodlabelling/submissions.nsf/lookupSubmissionAttachments/1WCME-85CSN920100512070110ABQI/$FILE/205a. pdf.
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a result of this incident, the use of gamma irradiation as an approved treatment on cat food was suspended. The importers were instructed to label all imported pet food (dog food) that underwent gamma irradiation processing with “must not be fed to cats”. To date, it has not been revealed what the toxic factor in the cat issue might have been. Not vitamin or nutrient depletion; not 'activation' of some strange minor component. The publication by Caulfield et al., 2008, holds 10 citations; none clearly revealing the issue. 6.9. Consumer concerns From the beginning several consumer organizations voiced concerns whether it would be ‘safe’ to consume irradiated food, at all. And a number of observations (see discussions above) were strong indications of unresolved issues. However, in now more than 100 years of research the questions raised are resolved and the consumers accept irradiated food where it has become available together with an understandable explanation of the new technology. This situation is not recognized by most consumer activists. Some consumer organizations have decided to continue their protests: namely the International Organisation of Consumer Unions (IOCU, today Consumer International), as well as Public Citizen and others; more details to be found on their WEBsites. The activities by IOCU in 1988 are most representative for this issue and discussed here to some extent.10 As participant to this international conference at Geneva, 1988, IOCU had failed to submit a manuscript; consequently, no presentation on their consumer issues and concerns was on the programme. In the contrary, a scientific presentation had been accepted, but IOCU complained this would not be their position and did not report to the meeting. Instead and against all rules of conduct, IOCU distributed their ‘Open Questions’ to the participants. The organizers even tolerated this and provided in the evening, outside the conference programme, for a presentation by IOCU with a response by recognized experts. These ‘answers’ refuted point by point the allegations raised by IOCU: But again, IOCU proved to be not open to factual and scientific discussion, instead they distributed another pamphlet. This situation is narrated here to a limited extend; it reveals the difficulty for scientists to make their results understandable also to opponents of their intentions.
7. Conclusions Any food processed by ionizing radiation up to any high dose is safe to consume, as long as it is palatable. In this aspect, irradiation is not different to other techniques; compare: the barbecue burned to coal! From time to time some unexpected effects are discovered which appear to shed light on hitherto undetected risks of food irradiation. But a thorough scientific evaluation reveals regularly that the observed effect is extremely small or just not relevant under practical circumstances. For example, 2-ACBs are potentially carcinogenic, but this is irrelevant under practical circumstances; on the other hand it serves for the reliable detection of unlabelled 10 Outstanding questions on the safety of irradiated food, IOCU (undated, 1988). Comments on IOCU's paper “Outstanding questions on the safety of irradiated food“, prepared by Professors Cliver, Diehl, Hawthorne and Kampelmacher, Temporary Advisors to the FAO/WHO/IAEA/ITC International Conference on Acceptance, Control of, and Trade in Irradiated Food, Geneva, Switzerland, 12 – 16 December 1988. IOCU press release (undated, 1988)Unfortunately, there are no publications available on this issue; however, this author (being a participant of this conference) holds a range of copies which are available upon request.
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D.A.E. Ehlermann / Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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irradiated food (fat containing). Ionizing radiation is difficult to understand by the ordinary consumer; and some consumer activists use this to manipulate the public perception. In the contrary, the scientific community is firmly convinced that irradiated food is safe to consume. The safety and wholesomeness of irradiated food has been re-confirmed again and again; national and international authorities have underlined this. Despite this the practical exploitation of radiation processing of food is still scarce; many governments are very reluctant to permit irradiated food on the market place; and also the food industry is not at all bringing the irradiated food to the market with confidence in consumer acceptance.
References References group A Codex, Alimentarius, 2003. General Standard for Irradiated Foods. Diehl, J.F., 1995. Safety of Irradiated Foods. Marcel Dekker, New York, 2nd edition. JECFI, 1963. Wholesomeness of irradiated food. FAO, Rome. WHO, 1994. Safety and Nutritional Adequacy of Irradiated Food. WHO, Geneva. WHO, 1991. Food Irradiation, A Technique for Preserving and Improving the Safety of Food. WHO, Geneva (revised edition of 1988).
References group B Renner, H.W., Reichelt, D., 1973. On the wholesomeness of high concentrations of free radicals in irradiated foods. V20. Zentralblatt fur Veterinarmedizin - Reihe B, pp. 648–660.
Further reading JCGHDI, 1999. High-dose irradiation: wholesomeness of food irradiated with doses above 10 kGy. Technical Reports Series 890. WHO, Geneva. JECFI, 1977. Wholesomeness of irradiated food. Technical Report Series no. 604. WHO, Geneva. JECFI, 1981. Wholesomeness of irradiated food. Technical Report Series 659. WHO, Geneva. JECFI, 1970. Wholesomeness of irradiated food with special reference to wheat, potatoes and onions. Technical Report Series no. 451. WHO, Geneva. JECFI, 1966. The technical basis for legislation on irradiated food. Technical Report Series no. 316. WHO, Geneva. Diehl, J.F., 1979. Food irradiation. Radiation Physics and Chemistry. Vol. 14(1–2), pp. 117–125. Diehl, J.F., Scherz, H., 1975. Estimation of radiolytic products as a basis for evaluating the wholesomeness of irradiated foods. Int. J. Appl. Radiat. Isot. 26 (9), 499–507. Ehlermann, D.A.E., 2014. Safety of food and beverages: safety of irradiated foods. In: Motarjemi, J. (Ed.), Encyclopedia of Food Safety, Vol. 3. Foods, Materials, Technologies and Risks 3. Academic Press, Elsevier, New York, pp. 447–452. Elias, P.S., 1980. The wholesomeness of irradiated food. Ecotoxicol. Environ. Saf. 4 (2), 172–183. Farkas, J., Mohácsi-Farkas, Csilla, 2011. History and future of food irradiation. Trends Food Sci. Technol. 22 (2–3), 121–126. Farkas, J., Ehlermann, D.A.E., Mohácsi-Farkas, Cs, 2014. Food technologies: food irradiation. In: Motarjemi, Y. (Ed.), Encyclopedia of Food Safety, Vol. 3. Foods, Materials, Technologies and Risks 3. Academic Press, Elsevier, New York, pp. 178–186. Hickman, J.R., 1959. Some notes on wholesomeness trials at Wantage. Int. J. Appl. Radiat. Isot. 6 (C), 258–260. Käferstein, F.K., Moy, G.G., 1993. Public health aspects of food irradiation. J. Public Health Policy 14 (2), 149–163. Reber, E.F., Raheja, K., Davis, D., 1966. Wholesomeness of irradiated foods. An annotated bibliography. Fed. Proc. 25 (5), 1529–1579. Swallow, A.J., 1991. Wholesomeness and safety of irradiated foods. Advances in Experimental Medicine and Biology. Vol. 289, pp. 11–31.
Please cite this article as: Ehlermann, D.A.E., Wholesomeness of irradiated food. Radiat. Phys. Chem. (2016), http://dx.doi.org/10.1016/j. radphyschem.2016.08.014i