Scientific Answers to Irradiation Bugaboos Fall 1999

by Marjorie Mazel Hecht

The anti-food irradiation litany repeats the same objections to food irradiation, no matter how many times each of the points has been answered in full by scientific researchers. Here, we summarize for readers the objections and the answers, giving sources for further documentation.

Objection: Food irradiation creates unique radiolytic products.

Response: The July 1986 report of the Council for Agricultural Science and Technology (CAST), which reviewed all the research work on food irradiation, defined unique radiolytic products “as compounds that are formed by treating foods with ionizing energy, but are not found normally in any untreated foods and are not formed by other accepted methods of food processing.”

The report states that “on the basis of this definition no unique radiolytic compounds have been found in 30 years of research. Compounds produced in specific foods by ionizing energy have always been found in the same foods when processed by other accepted methods or in other foods” (Vol. 1, p. 15).

Objection: Food irradiation causes vitamin loss.

Response. There is an extensive scientific literature dealing with food irradiation and vitamins over the past 45 years. In general, vitamins sensitive to heat are also sensitive to irradiation. It was found that vitamin retention is best when irradiation is carried out at low temperatures and in a vacuum (with the absence of oxygen) or when foods are dry. In general, scientists have concluded that “no significant adverse effects on the nutritional quality have been found in foods processed with ionizing energy relative to foods processed by conventional means” (CAST report, Vol. 1, p. 5).

One frequently cited comment by the opponents of food irradiation concerns the loss of vitamin C in irradiated potatoes. However, the specific finding is that the ascorbic acid in the potato shifts to dehydroascorbic acid. This change is “irrelevant from a nutritional point of view because dehydroascorbic acid has practically the same vitamin C activity as ascorbic acid,” as reported in the CAST report (Vol. 1, p. 29).

Objection: The Food and Drug Administration ignored any adverse studies in their 1988 ruling on food irradiation.

Response: The FDA has stated that there was no substance to allegations that it did not include adverse studies in making its rulings on food irradiation. The FDA answered each specific point of criticism in a 33-page document published in the Federal Register, Vol. 53, No. 251, Dec. 30, 1988. In this document, the FDA denies a request for a hearing on objections to its 1988 rule authorizing the use of food irradiation for pork and other foods, stating that “none of the objections has provided the information necessary to justify a hearing.”

Taking up the objections from food irradiation critics one by one, the FDA notes in each case that “a hearing will not be granted on the basis of mere allegations or general descriptions of positions and contentions.”

The FDA states that its Task Group did examine “in detail those studies [noted by the critics] that appeared on their face to show adverse effects. The Task Group found that because of problems associated with diet or inadequate experimental design, any adverse toxicological effects reported in these studies could not be attributed to irradiation of the food.”

Objection: Food irradiation caused polyploidy in India.

Response: Perhaps the most frequently cited objection to food irradiation by its opponents is based on a study by the National Institute of Nutrition in Hyderabad, India, in the mid-1970s that found polyploidy (chromosomal changes) in a small sample of malnourished children fed irradiated wheat.

Both an Indian government committee and an international committee determined that the conclusions of this study could not be supported by the data, that the study was faulty, and that the results were not reproducible. The Indian government committee found that “the frequency of 1.8 polyploid cells found in children eating freshly irradiated wheat was well within the normal range of healthy human beings” (as reported in the FDA statement in the Federal Register, Dec. 30, 1988, p. 53183).

Objection: Animals fed irradiated food developed abnormalities.

Response: In the Dec. 30, 1988 Federal Record, the FDA discusses the so-called adverse studies one by one, concluding that “studies with irradiated foods do not show adverse toxicological effects.” Specifically, the FDA evaluated 1984 studies conducted with mice to test the safety of radiation-sterilized chicken, noting that the signs of kidney damage “were the result of the high protein content of the chicken diets rather than of the irradiation of some diets”
(p. 53186).

As for studies with fruit flies fed radiation-sterilized chicken that had fewer progeny than a control group, the FDA noted that fruit flies are an “unreliable indicator of adverse reproductive effects” in human beings and that “mammalian data, which are more relevant to humans” do not show a pattern or trend indicative of adverse reproductive effects.”

In a study of hamsters fed irradiated fish, which critics said showed chromosome damage, the FDA noted that “the proportion of cells with the normal number of chromosomes was greater in the hamsters fed irradiated fish than in those fed the control diet” (p. 53190).

Objection: Irradiation will allow an increase in aflatoxin production.

Response: The studies cited about aflatoxin production involve the addition of aflatoxin-producing organisms to wheat after irradiation. The FDA stated that “it had no evidence that would lead it to conclude that food irradiated and stored under normal handling practices would show increased aflatoxin production” and that “infection with aflatoxin producing organisms would ordinarily occur before harvest” (as reported in the FDA statement in the Federal Register, Dec. 30, 1988, p. 53194).

As for concerns that malpractice in the storage of dry grains could lead to the growth of aflatoxin, the CAST report notes from the review of the research that “the available evidence [on the subject] indicates that treating grain with ionizing energy to control insects does not add to that hazard.”

Objection: Botulism could grow undetected after irradiation.

Response: The research on this topic indicates that with medium doses of irradiation “there are no microbiological safety problems with moist foods, such as fresh meats, poultry, and fish . . . as long as these foods are stored and distributed near the temperatures of ice (36 to 41 degrees F) (2 to 5 degrees C) according to good manufacturing practice.” The CAST report notes further that “As long as foods are refrigerated below 50 degrees F (10 degrees C), there is no microbiological safety problem for Clostridium botulinum types A and B” (Vol. 1, p. 32).

For Clostridium botulinum type E, however, which may be a concern with fresh fish, the CAST report notes that at doses of less than 2.2 kilograys, and particularly below 1.5 kilograys, “a diverse and active spoilage population remains to avoid toxin production by Clostridium botulinum type E” (CAST report, Vol. 1, p. 32). In other words, irradiation at lower doses reduces the microbial population but does not eliminate it, so that if irradiated fish is improperly refrigerated, it will begin to spoil and smell before the Clostridium botulinum type E could produce toxin.

Objection: Irradiation facilities will be a safety problem.

Response: Nuclear safety is one of the chief concerns mentioned by the groups opposing food irradiation. In particular, critics are concerned with nuclear waste disposal. This is a political problem, not a technical one. The technology of reprocessing nuclear waste, which eliminates 99 percent of it, is well known and used by other nuclear nations—but not by the United States. The technology also exists for long-term burial of waste in a vitrified form.

However, it seems certain that the food irradiation plants of the future will not use radionuclides for irradiation. They will use electron beam accelerators or X-ray sources to provide irradiation. This should eliminate opposition to food irradiation based on concerns with nuclear safety because no radioactive materials will be used.

Marjorie Mazel Hecht is the managing editor of 21st Century Science & Technology magazine.

Food irradiation eliminates 99.5 percent of all Salmonella, Listeria, and Campylobacter pathogens in chicken—without affecting freshness, taste, smell, texture, or wholesomeness.
(Photo: Philip Ulanowsky)
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