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]]]]]]]]]]]]]]]] 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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