]]]]]]]]]]]]]]]] FOOD IRRADIATION [[[[[[[[[[[[[[[ (7/20/1989) Information Letter No. 746 Health and Welfare Canada, Health Protection Branch 4 June 1988 [Kindly uploaded by Freeman 10602PANC] [The present paper excerpts those substantial portions of Information Letter No. 746 which deal with the health aspects of food irradiation. Material dealing with statutory, regulatory, definitional and other considerations has been omitted. The material presented is consistent with the proposition that ... irradiation of any food commodity up to an overall average dose of 10 kGy presents no toxicological hazard; hence toxicological testing of foods so treated is no longer required. World Health Organization, Wholesomeness of Irradiated Foods (1981) though the Canadian regulatory authorities prefer to ``examine each submission [for permission to irradiate a foodstuff] on a case-by-case basis to determine if additional or new toxicity testing is required''. I am most grateful to Mr Jaroslav Franta of the Committee for Accuracy in Nuclear Issues in the Media, 2252 Kaufman, Montreal, Quebec, Canada H4K 2G3, for providing me with a copy of the original document. -- Oleg Panczenko] [Pages 1-18 omitted.] [Page 19] Toxicology and Safety of Irradiated Foods [Apology for the technical level of this section omitted.] (18) ... [A] respondent expressed concern that some of the studies on irradiation [of food] had been conducted by Industrial Bio-Test Laboratories (IBT), an American firm implicated in improperly conducting many of the safety studies performed under contract to its clients. Finally, a respondent contended that only 1% (5) of the 413 studies available to the United States Food and Drug Administration (U.S.F.D.A.) appeared to support safety. [Paragraph omitted.] [Page 20] With regard to a limited number of studies on irradiated foods conducted by IBT, these have been discounted in connection with the recent review on the safety of irradiated foods undertaken by Branch toxicologists, insofar as there were available numerous replacement short and long-term studies performed by other reputable institutions investigating the toxicity of these particular foods and others. With regard to the numbers of studies that support safety, the U.S.F.D.A. (1986) indicted in its recent Federal Register document that: "Only 5 of the 441 studies reviewed ... were considered by agency reviewers to be properly conducted, fully adequate by 1980 toxicological standards, and able to stand alone in the support of safety." The operative phrase is the last one. The Federal Register article goes on to say: "Although most of the studies were generally inadequate by present day standards and could not stand alone to support safety, many contained individual components which, when examined either in isolation or collectively, allowed the conclusion that consumption of foods treated with low levels of irradiation did not appear to cause adverse toxicological effects." It is important to recognize that these studies were conducted for a myriad of reasons via many different protocols designed for many different purposes. A substantial percentage of these studies were conducted in an era prior to the "standardization" of several types of toxicity testing protocols. Although some of these studies may well be classified as inadequate in light of present standards, the fact remains that the essential findings and interpretations are valid and useful. [Page 21] It should be noted that other agencies, such as the U.S.F.D.A., and expert scientific and toxicological panels around the world such as the Joint Food and Agricultural Organization/ International Atomic Energy Agency/World Health Organization (FAO/IAEA/WHO) Expert Committee on Food Irradiation (1981), the United Kingdom Advisory Committee on Irradiated and Novel Foods (1986), and the United States Council for Agricultural Science and Technology (CAST; 1986) have reviewed the extensive toxicological data base and have attested to the overall safety of irradiated foods at doses of practical commercial importance. [Paragraph omitted.] (19) One respondent indicated that two relatively recent Russian studies demonstrated damage to the kidneys and testes of rats fed irradiated food. In the first paper by Levina and Ivanov (1978), the authors reported an increase of membranous-proliferative glomerulonephritis in kidneys of rats fed an irradiated laboratory diet for 20 months. The study (original scientific paper translated into English) has been evaluated by Health Protection Branch toxicologists. No quantitative data [page 22] were presented to asses the potential toxic effects of irradiated diet on kidneys. Neither were individual animal or summary data presented. The results did not define the frequency of kidney lesions for any of the experimental groups. Historical control data were not provided and the strain of rats employed in this work was not defined. It was concluded that the toxicological significance of these findings cannot be evaluated from the available data. In the second paper by Ivanov and Levina (1981), the authors reported an increase of degenerative changes (enlarged testes; differences in size and weight of right and left testes; degeneration of seminiferous tubules; proliferation of Leydig cells; signs of aspermatogenesis; coagulation necrosis) in the testes of 21-month-old rats fed gamma-irradiated (0.25-56 kGy) laboratory diet for a period of 20 months. An English translation of the report was evaluated by Branch toxicologists. The report did not specify the strain of rats used, the composition of the diet, animal housing conditions and the exact radiation doses used (only range given). The histological findings were not adequately defined or documented. Individual lesions observed were not defined quantitatively. It was thus concluded that the results were inadequate to determine the toxicological significance of the reported findings. It should be noted, however, that degenerative and atropic testicular lesions are relatively common in older rats (Goodman et al., 1979; Cotchin and Roe, 1967). (20) The same respondent cited a study (Bhaskaram and Sadasivan, 1975) in which malnourished children in India fed freshly-irradiated wheat (fed within 2 to 3 weeks of irradiation at a dose of 0.75 kGy) showed an increase in abnormal white blood cells (polyploidy). Also [page 23] cited was a study (Vijayalaxmi, 1978) in which polyploidy was observed in monkeys fed wheat irradiated at 0.75 kGy within 20 days of feeding. Branch toxicologists have assessed the significance of the studies undertaken at the National Institute of Nutrition, Hyderabad, India and consider that the following points are relevant in connection with evaluation of the study involving undeI/{;]rished Indian children: (a) Malnourished children are not considered to be the best test subjects available, since malnutrition alone is known to induce chromosomal aberrations. Furthermore, the background incidence of chromosomal aberrations among malnourished children may vary because it may be affected by the type and degree of malnutrition. No data on the background incidence of chromosomal aberrations in malnourished Indian children were provided. (b) The fact the study reported increased polyploidy (1.8%) in the lymphocytes of malnourished children fed freshly-irradiated (0.75 kGy) wheat, but none (0.0%) in children fed unirradiated wheat is unusual. Armendares et al., (1971) reported that malnourished Mexican children (age 1-60 months) exhibited a high incidence of chromosomal aberrations (12-21%) in lymphocytes relative to the background incidence of chromosomal aberrations in lymphocytes of well-fed children (2-4%). Health Protection Branch toxicologists have noted other work which is of relevance in addressing the polyploidy issue. In particular, Brynjolfsson (1986) has summarized the results of eight experiments conducted in China in which foods irradiated from 0.1 - 8.0 kGy were fed to a total of 439 human volunteers for a 7 to 15 week period. These experiments, which have also been cited in a recent [page 24] report of the Council for Agricultural Science and Technology (1986), were reported to reveal no increase in the incidence of polypoidy. In a study by Renner et al. (1982) no chromosomal aberrations, including polypolidy, were observed in the bone marrow of male and female Chinese hamsters fed irradiated cooked chicken (7.0 kGy, stored 5-8 days), dried dates (1.0 kGy) or cooked fish (2.5 kGy, stored 7-10 days) for a period of 6 days. Although an earlier study by Renner (1977) showed that a commercial diet, freshly irradiated at 30-45 kGy and fed to Chinese hamsters for a period of 1 day or 6 weeks, did increase the incidence of polyploidy cells in bone marrow 3-5 times that of controls (controls 0.06 - 0.08% vs treated 0.20 - 0.32%) the same diet irradiated at dose levels below 20 kGy caused no increase in polyploidy of other chromosomal aberrations. Based on all of the above considerations, the Branch has concluded that consumption of wheat irradiated up to the maximum absorbed dose permitted in Canada for this commodity (0.75 kGy) would not pose a hazard to the consumer. (21) The results of 12 United States Department of Agriculture (U.S.D.A.) sponsored studies were cited by one respondent in which chicken was exposed "to the same levels of radiation (56 kGy) being considered for future approval of meat and poultry". The respondent indicated that there were several findings indicating the toxicity of irradiated chicken fed to mice, in particular, the following noted in one of the studies: 1. A "statistically significant" increase in testicular tumors in mice fed Cobalt-60 (gamma) irradiated chicken meat (Group G). [Page 23] 2. Survival of both sexes in this group (Group G) was significantly reduced, at least in certain sub-groups, compared to the controls. 3. Many lesions (including cancer) which occurred infrequently and for which statistical analyses could not be performed, were often found most frequently in this group (Group G). 4. Thus, while there is no evidence of a highly toxic effect from diet G, the preponderance of evidence suggests some degree of toxicity was present. The respondent also expressed concern about "the significant adverse effect in Group G mice involving immune kidney disease ("glomerulonephropathy")". Finally, the respondent mentioned "a statistically significant dose-related increased rate of death in the offspring of flies fed gamma-irradiated chicken", this effect cited as being "consistent with chromosomal damage". It should be indicated that the branch has not considered nor is presently considering submissions for the irradiation of meat and poultry at 56 kGy. This is a sterilizing dose and the particular studies cited by this respondent were undertaken primarily to asses the feasibility and safety of preserving military rations in which the radiation treatment was applied to a canned, frozen product containing added salt. Most commercial interest in irradiating chicken has been and is likely to be in irradiating fresh or frozen whole birds or comminuted [ground, pulverized] chicken meat at doses sufficient to reduce Salmonella contamination. The doses are below 10 kGy, usually ranging from 3-7 kGy. Concerning the first finding mentioned above, Health Protection Branch toxicologists have reviewed this study thoroughly [page 26] and Branch statisticians have subjected the testicular interstitial cell tumour incidence data to statistical analysis. As a result, it was found that there was no statistically significant difference in the incidence of interstitial cell tumors in the male mice of gamma- or electron-irradiated meat groups when compared to the control (frozen meat) group. A committee of Health Protection Branch Pathologists examined microslides of testicular tissue from the animals considered to exhibit possible tumorigenicity. Branch pathologists agreed with the conclusions reached by other review groups, namely, that the observed benign testicular tumors were not treatment-related. The Health Protection Branch concludes that the available evidence does not support the view that benign testicular interstitial cell tumours, observed in male CD-1 mice in the evaluated study are related to consumption of gamma- or electron-irradiated chicken meat. Note: To assist the reader in the following discussion, the following designations for the various diets employed in the mouse irradiated chicken study were used: Group N (laboratory chow) Group F (35% frozen chicken meat; 65% laboratory chow) Group T (35% thermally-processed chicken meat; 65% laboratory chow) Group G (35% gamma-irradiated chicken meat; 65% laboratory chow) [Page 27] Group E (35% electron-irradiated chicken meat; 65% laboratory chow) The second issue related to decreased survival of mice. While survival was similar in all experimental groups at 15 months treatment, it decreased considerably after 15 months on test. At the end of the test period (24 months) the survival among all groups of mice fed laboratory chow/chicken meat was lower than those fed only laboratory chow (Group N). But in this experiment, it is really appropriate to consider Group F as the control group, because this diet unlike Groupe [sic] N contained (35%) chicken meat. While the females in the "non breeder" (i.e. those animals used only in the chronic/carcinogenicity study) Group G had a lower percentage survival than the other comparable groups (F, T and E), the various parameters measured for assessing toxicity (i.e. body weights, hematology, blood chemistry, gross pathology) did not support a treatment-related effect. It must also be noted that the percentage survival of females in the "breeder" (i.e. those animals used to produce F1 progenies for the multi-generational study and then used in the chronic/carcinogenicity study) Group G was the highest among the other comparable groups (F, T and E). One must consider that the "breeder" Group G mice may have consumed more diet (to maintain pregnancy) that the "non-breeder" Group G, and if irradiated chicken was responsible for decreased survival, one would have also expected higher mortality in the "breeders". Furthermore in similar studies with rats and dogs, survival was not adversely affected by consuming diets containing irradiated chicken meat. Thus, there is scientific justification to consider the percentage survival in the female "non-breeder" Group G as a spurious result. Such an [page 28] occasional spurious result can reasonably be expected when biological data from 20 experimental groups are collated. Concerning the third issue on frequency of occurrence of lesions, it should be indicated that spontaneous neoplastic lesions (including cancer) were observed among mice of all experimental groups of either "breeders" or "non-breeders" subgroups. The incidence of lesions was not associated with ingestion of irradiated chicken meat. As a matter of fact, the highest incidence of total neoplastic lesions was observed among control animals fed frozen chicken meat (Group F). The frequency of lesions observed was within the range of normal biological incidence for this strain of mice. The fourth point raised by this respondent was that while there is no evidence of highly toxic effect from diet G, the preponderance of evidence suggests some degree of toxicity was present. Based on an extensive toxicological review, it has been concluded that the experimental data do not demonstrate a treatment-related toxicological effect. Concerning immune kidney disease (glomerulonephropathy), the incidence of non-neoplastic lesions of kidney was high among animals of all experimental groups. [Page 29] The data showed that the incidence of the lesion was not associated with ingestion of irradiated chicken meat. Again, the highest incidence of the lesions was observed among animals fed frozen chicken meat (see below). Incidence (%) of kidney glomerulonephropathy for combined data ("breeders" and "non-breeders") Males Females Group N (laboratory chow) 8.2 22.4 Group F (Frozen chicken meat) 19.5 37.9 Group T (thermally processed meat) 9.0 29.2 Group G (gamma-irradiated meat) 15.0 35.8 Group E (electron-irradiated meat) 15.7 33.9 Finally, in regard to this respondent's concern about an increased rate of death in the offspring of flies reared on gamma-irradiated chicken meat, the study of the sex-linked recessive lethal test in Drosophila melanogaster produced non-mutagenic effects. However, a significant reduction in production of offspring (reproductive effect) in cultures of D. Melanogaster, reared on gamma-irradiated chicken meat was observed. A similar but much lower response occurred in cultures reared on the frozen chicken meat. The toxicological significance of this finding is doubtful as far as man is concerned. Extrapolation of the findings from the D. Melanogaster fly study to the human being is very difficult. Furthermore, the number of reproduction studies with experimental animals (mouse, rat, dog) reviewed by the Branch clearly demonstrated that ingestion of different [page 30] irradiated foods did not adversely affect reproductive parameters investigated. ... [Page 32] .. (25) ... In assessing the human health implications of dietary exposure to irradiated foods, all available information has been reviewed. Many countries, for example, Belgium, Japan, and the Netherlands (International Atomic Energy Agency; November, 1986) have had experience in irradiating individual food items, without reports of adverse effects on the human population. ... [Sections `Record-Keeping Requirement' and `Table of Positive Listings' omitted. `Introduction to `Comments Not Specifically Related to I.L. No. 651' omitted.] [Page 35] .. (1) The comment has been made that foods subjected to the irradiation process become radioactive. Using electronic or machine sources to produce X-rays or electron beams, it is possible to induce radioactivity in foods if such sources are operated at high energy levels. For this reason, constraints have been proposed for the energy levels of these types of radiation (5 MeVs for X-rays; 10 MeVs for electron beams). At these controlled energy levels, the experimentally-measured and possible theoretically induced activity is several thousand times less than the natural background level of radioactivity in food. The inherent energy levels of gamma-rays emitted by Cobalt-60 and Cesium-137 are too low to cause induced radioactivity. For the reasons outlined above, irradiated foods do not become radioactive as a result of this treatment. .. [Page 36] .. (3) The argument has been made that the Chernobyl nuclear disaster [26 April 1986] experience illustrated the dangers that can result from irradiating food. [Omitted paragraph states that radionuclides may be harmful to human tissues when inhaled or ingested.] In the case of irradiated food, the radionuclide source does not come in contact with food. Rather, the food is exposed to gamma-rays emitted by the source material. Thus, in the context of contamination of food by radionuclides, comparisons between the Chernobyl nuclear disaster and food irradiation are inappropriate and misleading. [Page 37] (4) Concern has been voiced about the production and persistence of free radicals. The formation of free radicals is not unique to food irradiation. Indeed, free radicals are formed by other types of physical processing of food such as cooking and canning. Free radicals are generally very short-lived in the presence of moisture and do not persist in foods. Even so-called dry foods such as wheat contain significant amounts of water (15%) and free radicals would not be expected to persist for any appreciable time in such a medium. In fact, in a study by Diehl (1972) whereby starch (the major constituent of wheat) containing 15% moisture was irradiated at a dose of 10 kGy, no free radical activity could be detected within one day of irradiation. Thus, in relation to the existing provisions the likelihood of there being any free radicals present in food as consumed is extremely remote. ... (5) It has been suggested that altered microbiological populations can cause radiation-resistant microorganisms of public health concern to multiply due to lack of competition from those destroyed. The oft-cited example used to support this contention is the assumption that relatively radiation-resistant Clostridium botulism spores will grow unabated in food irradiated at 10 kGy due to competitor spoilage organisms being destroyed. Like other conventional non-sterilizing processing techniques (e.g. pasteurization), irradiation up to 10 kGy will not destroy C. botulism spores. As is the case following application of these other techniques, proper storage and refrigeration conditions must be employed to [page 37] ensure against outgrowth of C. botulism spores, if present. The Board of the International Committee on Food Microbiology and Hygiene of the International Union of Microbiological Societies at their meeting in Copenhagen, 1982, also concluded that the alteration of microbial populations after irradiation is similar to that which occurs after other conventional processes such as pasteurization. The Board viewed food irradiation as an important additional process to control foodborne pathogens and did not present any additional health hazards. ... (6) It has been alleged that the process can lead to enhanced aflatoxin production by microorganisms. This allegation may be based on a laboratory experiment (Schindler et al., 1980) which showed apparently higher aflatoxin production of irradiated spores. This experiment is not considered to be relevant to food irradiation because it was carried out under conditions not encountered in commercial practice. Also, some studies have shown that the irradiation process itself can actually destroy aflatoxin and other toxins in food (Temcharoen and Thilly, 1982; Jaddou et al., 1983). REFERENCES [Selected references only.] 1. Advisory Committee on Irradiated and Novel Foods. Report on the Safety and Wholesomeness of Irradiated Foods. London, 1986. Her Majesty's Stationery Office, P.O. Box 276, London SW8 5DT. 2. Armendares, S., Salamanca, F. and Frenk, S. 1971. Chromosome abnormalities in severe protein calorie malnutrition. Nature 232: 271-273. 5. Bhaskarem, C. and Sadasivan, G. 1975. Effects of feeding irradiated wheat to malnourished children. Am. J. Clin. Nutr., 28: 130-135. 7. Brynjolfosson, A. 1987. Results of feeding trials of irradiated diets in human volunteers: Summary of the Chinese studies reported at FAO/IAEA seminar for Asia and the Pacific on the practical application for food irradiation. Food Irradiation Newsletter, 11(1): 33-41. 8. Cotchin, E. and Roe, F.G.C. 1967. Pathology of Laboratory Rat and Mice. p. 781. 9. Council for Agricultural Science and Technology. Ionizing Energy in Food Processing and Pest Control: I. Wholesomeness of Food Treated With Ionizing Energy. Ames, Iowa, 1986. Report No. 109. Available from Council for Agricultural Science and Technology, 137 Lynn Avenue, Ames, Iowa 50010-7120. 10. Diehl, J.F. 1972. Elektronenspinresonanz-Untersuchungen an strahlenkonservierten Lebensmitteln. 11. Einfuss des Wassergehaltes auf die Spinkonzentration. Lebensm.-Wiss. Technol., 5: 51. 11. Goodman, D.G., Ward, J.M., Squire, R.A., Chu, K.C. and Linhart, M.S. 1979. Neoplastic and non-neoplastic lesions in aging F344 rats. Toxicol. Appl. Pharmacol. 48: 237-248. 13. International Atomic Energy Agency. November 1986. "Commercialization of Food Irradiation". Article from: Food Irradiation Newsletter 2(10): 48-52. 14. Ivanov, A.E. and Levina, A.I. 1981. Pathomorphological changes in the testes of rats fed on products irradiated with gamma-rays. Byull. Eksp. Biol. Med. 91(2): 233-236. 15. Jaddou, H., Al-Hakim, M., Al-Adamy, L.Z. and Mhaisen, M.T. 1983. Effect of gamma-radiation on gossypol in cottonseed meal. J. Fd. Sci., 48: 988-989. 16. Levina, A.I. and Ivanov, A.E. 1978. Pathomorphology of the kidneys in rats after prolonged ingestion of irradiated foods. Byull. Eksp. Biol. Med. 85(2): 230-232. 17. Renner, H.W. 1977. Chromosome studies on bone marrow cells of Chinese hamsters fed a radiosterilized diet. Toxicology 8: 213-222. 18. Renner, H.W., Graff, U., Wurgler, F.E., Altmann, H., Asquith, J.C. and Elias, P.S. 1982. An investigating of the genetic toxicology of irradiated foodstuffs using short-term test systems. III-In vivo tests in small rodents and in Drosophila Melanogaster. Fd. Chem. Toxicol. 20: 867-878. 19. Schindler, A.F., Abadie, A.N. and Simpson, R.E. 1980. Enhanced aflatoxin production by Aspergillus flavus and Aspergillus parasiticus after gamma irradiation of the spore inoculum. J. Fd. Prot., 43: 7-9. 20. Temcharoen, P. and Thilly, Wm. G. 1982. Removal of Aflatoxin B1 toxcicity but not mutagenicity by 1 megarad gamma irradiation of peanut meal. J. Food Safety, 4: 199-205. 22. U.S. Food and Drug Administration. 1986. 21 CFR Part 179. Irradiation in the Production, Processing, and Handling of Food; Final Rule. Federal Register, 51(75): 13376-13399. 23. Vijayalaxmi, C. 1978. Cytogenetic studies in monkeys fed irradiated wheat. Toxicology, 9: 181-184. 24. World Health Organization. Wholesomeness of Irradiated Food. Geneva, 1981. World Health Organization Technical Report Series No. 659. * * *
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