The Role of Irradiation in Food Safety
http://www.100md.com
《新英格兰医药杂志》
An estimated 76 million cases of foodborne disease, resulting in more than 325,000 hospitalizations and 5000 deaths, occur in the United States annually.1 Important sources of foodborne pathogens include contaminated produce and improperly cooked, handled, or stored meat and poultry products. The meat and poultry industry's efforts at surveillance and intervention have reduced, but not eliminated, microbial contamination of meat and poultry carcasses.2,3 Despite these efforts, consumers continue to have preventable illnesses and even to die as a result of microbial contamination of foods. The irradiation of food has the potential to decrease the incidence of foodborne disease dramatically. It is widely supported by international and national medical, scientific, and public health organizations, as well as groups involved with food processing and food services (Table 1). Currently, the technology for irradiating food is underused. In the United States, only 10 percent of herbs and spices and less than 0.002 percent of fruits, vegetables, meats, and poultry are irradiated.4
Table 1. Selected Organizations That Support the Safety of Irradiated Food.
Slow acceptance of irradiation may be due to several factors. First, the term "irradiation" is sometimes confusing or alarming to consumers because of its apparent, but nonexistent, association with radioactivity. Second, the causes and prevention of foodborne disease are poorly understood by the public. Third, health professionals and the media are largely unaware of the benefits of irradiating food. Finally, an anti-irradiation campaign has been conducted by certain groups because of their beliefs about food, nuclear power, and agricultural economics.
Technology of Food Irradiation
Radiation is energy transmitted through space in the form of electromagnetic waves, which may be considered rays or particles. Food irradiation involves the use of high-energy radiation in any of three approved forms: gamma rays, x-rays, or electron beams. Gamma rays can be generated by either of two approved radionuclide sources, cobalt-60 or cesium-137, whereas x-rays and electron beams are generated electrically.
Doses of radiation used in food processing are measured in units of grays (Gy) or kilograys (kGy), with 1 Gy equal to 100 rad. Convention divides doses into three categories by application: less than 1 kGy (low dose) for disinfestation and the extension of shelf life; 1 to 10 kGy (pasteurizing dose) for pasteurization of meats, poultry, and other foods; and more than 10 kGy (high dose) for sterilization or for the reduction of the number of microbes in spices.5
Commercial irradiation of meats and poultry is conceptually similar to the pasteurization of milk. Pasteurization is defined as the critical reduction of pathogens in a substance, especially a liquid (e.g., milk), at a temperature and for a period of time that destroy objectionable organisms without major chemical alteration of the substance, or the critical reduction of pathogens in perishable food products (e.g., fruit or fish) with radiation (e.g., gamma rays).6 Heat pasteurization kills or inhibits the growth of pathogens in raw milk, but the surviving nonpathogenic bacteria can eventually cause the milk to spoil if it is stored for extended periods of time or mishandled. Similarly, pasteurization by irradiation is not intended to eliminate all bacteria in meat and poultry but, rather, to eliminate all pathogenic microorganisms.7
Thus, pasteurization by irradiation does not eliminate the need for safe food handling and cooking but, rather, helps reduce the dangers of primary contamination and cross-contamination. Sterilization by irradiation requires a radiation dose that is approximately 10 to 30 times the dose required for pasteurization and is defined by its ability to achieve a reduction in Clostridium botulinum spores of at least 12 log, which is the standard level of microbial reduction in commercial canning.8
The Status of Food Irradiation
A comprehensive historical review of food irradiation has been published by Josephson.9 In 1958, Congress revisited the federal Food, Drug, and Cosmetic Act of 1938 and added to it the Food Additives Amendment, which classifies food irradiation as a food additive. This is incorrect, since no substance is physically added to the food. The defense of this classification has been that irradiation induces a chemical change in the food. However, baking, broiling, frying, grilling, canning, microwaving, and freeze-drying all induce such changes but are classified as processes.
In the United States, irradiation of food is approved for eliminating or sterilizing insects, extending shelf life, controlling pathogens and parasites, and inhibiting the sprouting of vegetables.4 Foods approved for irradiation include red meat, poultry, pork, fruits and vegetables, aromatic spices, seeds, herbs and seasonings, enzyme preparations, eggs, and wheat.4 Shellfish and processed meats are under review for approval for irradiation.
Food Irradiation and Public Health
The World Health Organization and the European Commission's Scientific Committee on Food have assessed the safety and benefits of food irradiation.10,11 In addition, the science of food irradiation has been extensively reviewed.12,13,14,15,16,17 The food industry's standard approach to ensuring the safety of food involves analyzing production processes and anticipating safety hazards at critical control points. Irradiation is an effective critical control point for most bacterial pathogens, including Escherichia coli O157:H7, salmonella, campylobacter, and listeria, as well as for parasites such as toxoplasma and trichinella.16,18 The Centers for Disease Control and Prevention estimates that if food irradiation were used for 50 percent of the meat and poultry consumed in the United States, there would be 900,000 fewer cases of foodborne illnesses annually and 352 fewer deaths due to foodborne illnesses.16 Since many cases of foodborne illness are likely to be unreported and undetected, the actual reduction would probably be even greater.
Hospitals and long-term care facilities have used sterilization by irradiation on a limited basis to provide immunocompromised patients with microbiologically safe meals that are more varied and higher in quality than meals prepared with the use of thermal sterilization alone.8,12 The National Aeronautics and Space Administration has used irradiation to sterilize astronauts' meals, and this method of sterilization has also been used to provide foods with an extended shelf life to the military and outdoor enthusiasts.19
Irradiation makes possible the replacement of toxic and environmentally harmful chemical fumigants such as ethylene oxide, propylene oxide, and methyl bromide.20 Irradiation also can increase the shelf life of certain foods and decrease losses from spoilage and pests. Reducing losses is particularly important in the context of the global distribution and storage of food.21,22 The cost to the consumer of irradiating food in large volumes is estimated to be less than five cents a pound for meat or poultry.23
Limitations of Irradiation
The irradiation of food is not a panacea. Bacterial spores are more resistant to irradiation than are vegetative cells and require doses substantially higher than those used in pasteurization.12 In general, inactivation of viruses also requires higher doses of radiation than those used in phytosanitary treatment (i.e., treatment to eliminate or sterilize pests in plant products) or pasteurization.8,12 This is relevant for foods that will not be cooked or otherwise processed before consumption (e.g., fresh produce). Preventing fecal contamination of such food items is the primary method of preventing foodborne viral diseases. Toxins and prions are not eliminated by irradiation at standard commercial doses.12 Irradiation of food does not prevent subsequent contamination by food-service workers or consumers.
The effect of irradiation on the color, odor, and texture of foods is variable and depends on dose, temperature, oxygen level, and packaging. Some sensory assessments of irradiated foods have revealed taste, color, or odor degradation, whereas others have shown minor or no differences in sensory characteristics between irradiated and nonirradiated foods.24,25,26 Recent improvements in food-irradiation techniques are expected to reduce or eliminate the effect of the process on sensory quality.13 Some fruits, vegetables, and dairy products undergo degradation in shelf life and quality after irradiation and thus are not good candidates for the process.
Arguments by Opponents
There are at least three prominent arguments against the irradiation of food. The first argument is that 2-alkylcyclobutanones (2-ACBs), which are unique to irradiated foods, are oncogenic and mutagenic in animals and are harmful to people who consume irradiated food. This claim refers to European research findings from 2002.27,28 The authors of the studies did not investigate the safety of irradiated foods but did report that formulations of chemically synthesized 2-ACBs, in concentrations about 1000 times those found in irradiated foods, had genotoxic and cytotoxic properties in vitro27 and that in rats treated with a known carcinogen, exposure to those concentrations of 2-ACBs may promote the development of tumors.28 The authors specifically cautioned against using their data to indict food irradiation.27 The European Commission's Scientific Committee on Food reviewed the research and, affirming its support of the World Health Organization's assessment of irradiation safety, concluded that evidence of genotoxicity had not been established by standard methods and that the findings could not be considered relevant to the question of the safety of irradiated food products.29
Numerous studies involving the feeding of irradiated foods to animals and humans have been de facto tests of the safety of 2-ACBs but have not shown them to be toxic or oncogenic.19,30 In addition, Ames assays (in vitro reverse mutation assays performed with histidine-dependent Salmonella enterica serovar typhimurium) and E. coli reverse mutation assays of 2-ACBs have shown no genotoxicity.24,31 Given the available evidence, any claim that the current studies of 2-ACBs are relevant to the safety of irradiated foods is lacking in scientific credibility.
The second argument is that irradiation destroys the nutritional quality of food. The addition of any energy to food can break down its nutrients and molecules. In general, macromolecules such as carbohydrates, proteins, and fats are not appreciably affected by irradiation.32 Thiamine (vitamin B1) is among the vitamins most sensitive to radiation, but food irradiation is not considered to threaten thiamine in the diet. A review by the Food and Drug Administration32 and an independent Argentinean study33 have concluded that irradiation poses no important risk to any nutrient in the diet, a conclusion supported by the American Dietetic Association.34
The third argument is that irradiation is a quick fix and a technological solution to a policy problem. Food irradiation has been portrayed as an easy way for industry and government to cover up or ignore the state of sanitation in processing facilities for meat and poultry. Traditional safety measures have the primary role in ensuring the safety of our meat supply, but they will not eliminate all contamination, particularly in a slaughterhouse environment. For example, testing for E. coli O157:H7 in ground beef by the Department of Agriculture's Food Safety and Inspection Service in 2003 showed that only 0.32 percent is contaminated.35 Because the United States produces about 3.6 billion kg (8 billion lb) of ground beef annually, even this exceedingly low level of contamination means annual production of an estimated 11.6 million kg (25.6 million lb) of ground beef that is contaminated with E. coli O157:H7.35 Irradiation cannot prevent primary contamination, but it can help ensure that contaminated ground beef does not reach the marketplace.
Future Opportunities
Food irradiation is at a crossroads in the United States. Good opportunities for large-scale implementation of food irradiation are emerging. For example, as of January 2004, the Department of Agriculture has begun to offer irradiated ground beef as part of the National School Lunch Program, which provides daily meals to approximately 27 million children nationwide. Furthermore, it is anticipated that the Food and Drug Administration will soon approve a request to authorize irradiation of cold cuts and processed meats; this will provide an important opportunity to reduce the risk of diseases such as listeriosis.
As irradiated foods become widely available, public demand and public health advocacy groups will determine whether the irradiation of food will extend beyond its current niche to have a measurable effect on food safety. In the 1930s and 1940s, physicians and allied health professionals had an important role in consumers' acceptance of the pasteurization of milk. As health advocates, they need to fill that role again in the adoption of food irradiation. It is important for physicians and other health professionals to be able to answer patients' questions accurately regarding the irradiation of food; to recommend irradiated foods, particularly for immunocompromised people, pregnant women, children, and the elderly; to encourage local and state medical professional organizations to endorse the use of irradiated products; to encourage grocers to stock irradiated foods; and to support the use of irradiated beef in school lunch programs.
Dr. Osterholm reports that in his role as director of the Center for Infectious Disease Research and Policy he has received unrestricted grant support from Robins, Kaplan, Miller & Ciresi; the Foundation for Education, Public Health, and Social Justice; the United Health Foundation; the 3M Foundation; SureBeam; Ecolab; and Ion Beam Applications.
Source Information
From the Center for Infectious Disease Research and Policy (M.T.O., A.P.N.) and the School of Public Health, University of Minnesota (M.T.O.) — both in Minneapolis.
References
Mead PS, Slutsker L, Dietz V, et al. Food-related illness and death in the United States. Emerg Infect Dis 1999;5:607-625.
Foodborne Outbreak Response and Surveillance Unit. 2000 Foodborne diseases outbreaks due to bacterial etiologies. (Accessed April 8, 2004, at http://www.cdc.gov/foodborneoutbreaks/us_outb/fbo2000/bacterial00.htm.)
Food Safety and Inspection Service. 2003 Recall cases. (Accessed April 8, 2004, at http://www.fsis.usda.gov/OA/recalls/rec_actv.htm#2003.)
Food irradiation: available research indicates that benefits outweigh risks. Washington, D.C.: General Accounting Office, August 2000. (GAO/RCED-00-217.)
Loaharanu P. Irradiated foods. 5th ed. rev. New York: American Council on Science and Health, May 2003.
Merriam-Webster online. (Accessed April 8, 2004, at http://www.merriam-webster.com.)
Dickson JS. Radiation inactivation of microorganisms. In: Molins RA, ed. Food irradiation: principles and applications. New York: John Wiley, 2001:23-36.
Molins RA. Irradiation of meats and poultry. In: Molins RA, ed. Food irradiation: principles and applications. New York: John Wiley, 2001:131-92.
Josephson ES. An historical review of food irradiation. J Food Saf 1983;5:161-89.
Revision of the opinion of the Scientific Committee on Food on the irradiation of food. Brussels: European Commission, April 4, 2003. (Accessed April 8, 2004, at http://europa.eu.int/comm/food/fs/sc/scf/out193_en.pdf.)
Wholesomeness of irradiated food: report of a joint FAO/IAEA/WHO Expert Committee. World Health Organ Tech Rep Ser 1981;659:1-34.
Diehl JF. Safety of irradiated foods. 2nd ed. New York: Marcel Dekker, 1995.
Satin M. Food irradiation: a guidebook. 2nd ed. Boca Raton, Fla.: CRC Press, 1996.
Farkas J. Irradiation as a method for decontaminating food: a review. Int J Food Microbiol 1998;44:189-204.
Diehl JF. Food irradiation — past, present and future. Radiat Phys Chem 2002;63:211-5.
Tauxe RV. Food safety and irradiation: protecting the public from foodborne infections. Emerg Infect Dis 2001;7:Suppl:516-521.
Thayer DW, Christopher JP, Campbell LA, et al. Toxicology studies of irradiation-sterilized chicken. J Food Prot 1987;50:278-288.
Molins RA, Motarjemi Y, K?sferstein FK. Irradiation: a critical control point in ensuring the microbiological safety of raw foods. Food Contr 2001;12:347-56.
de Bruyn IN. The application of high dose food irradiation in South Africa. Radiat Phys Chem 2000;57:223-5.
Giddings G. Commercial food irradiation in the United States. Radiat Phys Chem 1996;48:364-5.
Crawford LM. Challenges and opportunities for food irradiation in the 21st century. In: Loaharanu P, Thomas P, eds. Irradiation for food safety and quality. Lancaster, Pa.: Technomic Publishing, 2001:9-16.
Food loss prevention in perishable crops. Agricultural services bulletin no. 43. Rome: Food and Agriculture Organization of the United Nations, 1981. (Accessed April 8, 2004, at http://www.fao.org/docrep/s8620e/s8620e00.htm.)
Frenzen PD, Majchowicz A, Buzby JC, Imhoff B. Consumer acceptance of irradiated meat and poultry products. In: Issues in food safety economics. USDA/ERS agriculture information bulletin no. 757. Washington, D.C.: Department of Agriculture, August 2000.
The truth about irradiated meat. Consumer Reports. August 2003:34-7. (Also available at http://www.consumerreports.org/main/content/display_report.jsp?FOLDER%3C%3Efolder_id=341223&ASSORTMENT%3C%3East_id=333139&bmUID=1080132339051.)
Andrews LS, Ahmedna M, Grodner RM, et al. Food preservation using ionizing radiation. Rev Environ Contam Toxicol 1998;154:1-53.
Wheeler TL, Shackelford SD, Koohmaraie M. Trained sensory panel and consumer evaluation of the effects of gamma irradiation on palatability of vacuum-packaged frozen ground beef patties. J Anim Sci 1999;77:3219-3224.
Burnouf D, Delincée H, Hartwig A, et al. Toxicological study to assess the risk associated with the consumption of irradiated fat-containing food. Final report INTERREG II Project no. 3.171. Karlsruhe, Germany: Bundesforschungsanstalt für Ern?hrung, 2002:1-198. (BFE-R–02-02.) (In French and German.) (Accessed April 8, 2004, at http://www.bfa-ernaehrung.de/Bfe-Deutsch/Information/e-docs/bfer0202.pdf.)
Raul F, Gossé F, Delincée H, et al. Food-borne radiolytic compounds (2-alkylcyclobutanones) may promote experimental colon carcinogenesis. Nutr Cancer 2002;44:189-191.
Statement of the Scientific Committee on Food on a report on 2-alkylcyclobutanones. Brussels: European Commission, July 3, 2002. (Accessed April 8, 2004, at http://www.iaea.or.at/icgfi/documents/out135_en.pdf.)
Barna J. Compilation of bioassay data on the wholesomeness of irradiated food items. Acta Aliment 1979;8:205-315.
Sommers CH. 2-Dodecylcyclobutanone does not induce mutations in the Escherichia coli tryptophan reverse mutation assay. J Agric Food Chem 2003;51:6367-6370.
Food and Drug Administration. Irradiation in the production and handling of food: 21 CFR part 179. Fed Regist 1997;62:64107-64107.
Narvaiz P, Ladomery L. Estimation of the effect of food irradiation on total dietary intake of vitamins as compared with dietary allowances: study for Argentina. Radiat Phys Chem 1996;48:360-1.
Wood OB, Bruhn CM. Position of the American Dietetic Association: food irradiation. J Am Diet Assoc 2000;100:246-253.
Roybal J. Beef industry logs successful week in E. coli O157:H7 battle. BEEF Magazine's Cow-Calf Weekly. September 26, 2003. (Accessed April 8, 2004, at http://www.beef-mag.com/Microsites/Index.asp?pageid=8044&srid=11116&magazineid=13&siteid=5#a030926_4.)(Michael T. Osterholm, Ph.)
Table 1. Selected Organizations That Support the Safety of Irradiated Food.
Slow acceptance of irradiation may be due to several factors. First, the term "irradiation" is sometimes confusing or alarming to consumers because of its apparent, but nonexistent, association with radioactivity. Second, the causes and prevention of foodborne disease are poorly understood by the public. Third, health professionals and the media are largely unaware of the benefits of irradiating food. Finally, an anti-irradiation campaign has been conducted by certain groups because of their beliefs about food, nuclear power, and agricultural economics.
Technology of Food Irradiation
Radiation is energy transmitted through space in the form of electromagnetic waves, which may be considered rays or particles. Food irradiation involves the use of high-energy radiation in any of three approved forms: gamma rays, x-rays, or electron beams. Gamma rays can be generated by either of two approved radionuclide sources, cobalt-60 or cesium-137, whereas x-rays and electron beams are generated electrically.
Doses of radiation used in food processing are measured in units of grays (Gy) or kilograys (kGy), with 1 Gy equal to 100 rad. Convention divides doses into three categories by application: less than 1 kGy (low dose) for disinfestation and the extension of shelf life; 1 to 10 kGy (pasteurizing dose) for pasteurization of meats, poultry, and other foods; and more than 10 kGy (high dose) for sterilization or for the reduction of the number of microbes in spices.5
Commercial irradiation of meats and poultry is conceptually similar to the pasteurization of milk. Pasteurization is defined as the critical reduction of pathogens in a substance, especially a liquid (e.g., milk), at a temperature and for a period of time that destroy objectionable organisms without major chemical alteration of the substance, or the critical reduction of pathogens in perishable food products (e.g., fruit or fish) with radiation (e.g., gamma rays).6 Heat pasteurization kills or inhibits the growth of pathogens in raw milk, but the surviving nonpathogenic bacteria can eventually cause the milk to spoil if it is stored for extended periods of time or mishandled. Similarly, pasteurization by irradiation is not intended to eliminate all bacteria in meat and poultry but, rather, to eliminate all pathogenic microorganisms.7
Thus, pasteurization by irradiation does not eliminate the need for safe food handling and cooking but, rather, helps reduce the dangers of primary contamination and cross-contamination. Sterilization by irradiation requires a radiation dose that is approximately 10 to 30 times the dose required for pasteurization and is defined by its ability to achieve a reduction in Clostridium botulinum spores of at least 12 log, which is the standard level of microbial reduction in commercial canning.8
The Status of Food Irradiation
A comprehensive historical review of food irradiation has been published by Josephson.9 In 1958, Congress revisited the federal Food, Drug, and Cosmetic Act of 1938 and added to it the Food Additives Amendment, which classifies food irradiation as a food additive. This is incorrect, since no substance is physically added to the food. The defense of this classification has been that irradiation induces a chemical change in the food. However, baking, broiling, frying, grilling, canning, microwaving, and freeze-drying all induce such changes but are classified as processes.
In the United States, irradiation of food is approved for eliminating or sterilizing insects, extending shelf life, controlling pathogens and parasites, and inhibiting the sprouting of vegetables.4 Foods approved for irradiation include red meat, poultry, pork, fruits and vegetables, aromatic spices, seeds, herbs and seasonings, enzyme preparations, eggs, and wheat.4 Shellfish and processed meats are under review for approval for irradiation.
Food Irradiation and Public Health
The World Health Organization and the European Commission's Scientific Committee on Food have assessed the safety and benefits of food irradiation.10,11 In addition, the science of food irradiation has been extensively reviewed.12,13,14,15,16,17 The food industry's standard approach to ensuring the safety of food involves analyzing production processes and anticipating safety hazards at critical control points. Irradiation is an effective critical control point for most bacterial pathogens, including Escherichia coli O157:H7, salmonella, campylobacter, and listeria, as well as for parasites such as toxoplasma and trichinella.16,18 The Centers for Disease Control and Prevention estimates that if food irradiation were used for 50 percent of the meat and poultry consumed in the United States, there would be 900,000 fewer cases of foodborne illnesses annually and 352 fewer deaths due to foodborne illnesses.16 Since many cases of foodborne illness are likely to be unreported and undetected, the actual reduction would probably be even greater.
Hospitals and long-term care facilities have used sterilization by irradiation on a limited basis to provide immunocompromised patients with microbiologically safe meals that are more varied and higher in quality than meals prepared with the use of thermal sterilization alone.8,12 The National Aeronautics and Space Administration has used irradiation to sterilize astronauts' meals, and this method of sterilization has also been used to provide foods with an extended shelf life to the military and outdoor enthusiasts.19
Irradiation makes possible the replacement of toxic and environmentally harmful chemical fumigants such as ethylene oxide, propylene oxide, and methyl bromide.20 Irradiation also can increase the shelf life of certain foods and decrease losses from spoilage and pests. Reducing losses is particularly important in the context of the global distribution and storage of food.21,22 The cost to the consumer of irradiating food in large volumes is estimated to be less than five cents a pound for meat or poultry.23
Limitations of Irradiation
The irradiation of food is not a panacea. Bacterial spores are more resistant to irradiation than are vegetative cells and require doses substantially higher than those used in pasteurization.12 In general, inactivation of viruses also requires higher doses of radiation than those used in phytosanitary treatment (i.e., treatment to eliminate or sterilize pests in plant products) or pasteurization.8,12 This is relevant for foods that will not be cooked or otherwise processed before consumption (e.g., fresh produce). Preventing fecal contamination of such food items is the primary method of preventing foodborne viral diseases. Toxins and prions are not eliminated by irradiation at standard commercial doses.12 Irradiation of food does not prevent subsequent contamination by food-service workers or consumers.
The effect of irradiation on the color, odor, and texture of foods is variable and depends on dose, temperature, oxygen level, and packaging. Some sensory assessments of irradiated foods have revealed taste, color, or odor degradation, whereas others have shown minor or no differences in sensory characteristics between irradiated and nonirradiated foods.24,25,26 Recent improvements in food-irradiation techniques are expected to reduce or eliminate the effect of the process on sensory quality.13 Some fruits, vegetables, and dairy products undergo degradation in shelf life and quality after irradiation and thus are not good candidates for the process.
Arguments by Opponents
There are at least three prominent arguments against the irradiation of food. The first argument is that 2-alkylcyclobutanones (2-ACBs), which are unique to irradiated foods, are oncogenic and mutagenic in animals and are harmful to people who consume irradiated food. This claim refers to European research findings from 2002.27,28 The authors of the studies did not investigate the safety of irradiated foods but did report that formulations of chemically synthesized 2-ACBs, in concentrations about 1000 times those found in irradiated foods, had genotoxic and cytotoxic properties in vitro27 and that in rats treated with a known carcinogen, exposure to those concentrations of 2-ACBs may promote the development of tumors.28 The authors specifically cautioned against using their data to indict food irradiation.27 The European Commission's Scientific Committee on Food reviewed the research and, affirming its support of the World Health Organization's assessment of irradiation safety, concluded that evidence of genotoxicity had not been established by standard methods and that the findings could not be considered relevant to the question of the safety of irradiated food products.29
Numerous studies involving the feeding of irradiated foods to animals and humans have been de facto tests of the safety of 2-ACBs but have not shown them to be toxic or oncogenic.19,30 In addition, Ames assays (in vitro reverse mutation assays performed with histidine-dependent Salmonella enterica serovar typhimurium) and E. coli reverse mutation assays of 2-ACBs have shown no genotoxicity.24,31 Given the available evidence, any claim that the current studies of 2-ACBs are relevant to the safety of irradiated foods is lacking in scientific credibility.
The second argument is that irradiation destroys the nutritional quality of food. The addition of any energy to food can break down its nutrients and molecules. In general, macromolecules such as carbohydrates, proteins, and fats are not appreciably affected by irradiation.32 Thiamine (vitamin B1) is among the vitamins most sensitive to radiation, but food irradiation is not considered to threaten thiamine in the diet. A review by the Food and Drug Administration32 and an independent Argentinean study33 have concluded that irradiation poses no important risk to any nutrient in the diet, a conclusion supported by the American Dietetic Association.34
The third argument is that irradiation is a quick fix and a technological solution to a policy problem. Food irradiation has been portrayed as an easy way for industry and government to cover up or ignore the state of sanitation in processing facilities for meat and poultry. Traditional safety measures have the primary role in ensuring the safety of our meat supply, but they will not eliminate all contamination, particularly in a slaughterhouse environment. For example, testing for E. coli O157:H7 in ground beef by the Department of Agriculture's Food Safety and Inspection Service in 2003 showed that only 0.32 percent is contaminated.35 Because the United States produces about 3.6 billion kg (8 billion lb) of ground beef annually, even this exceedingly low level of contamination means annual production of an estimated 11.6 million kg (25.6 million lb) of ground beef that is contaminated with E. coli O157:H7.35 Irradiation cannot prevent primary contamination, but it can help ensure that contaminated ground beef does not reach the marketplace.
Future Opportunities
Food irradiation is at a crossroads in the United States. Good opportunities for large-scale implementation of food irradiation are emerging. For example, as of January 2004, the Department of Agriculture has begun to offer irradiated ground beef as part of the National School Lunch Program, which provides daily meals to approximately 27 million children nationwide. Furthermore, it is anticipated that the Food and Drug Administration will soon approve a request to authorize irradiation of cold cuts and processed meats; this will provide an important opportunity to reduce the risk of diseases such as listeriosis.
As irradiated foods become widely available, public demand and public health advocacy groups will determine whether the irradiation of food will extend beyond its current niche to have a measurable effect on food safety. In the 1930s and 1940s, physicians and allied health professionals had an important role in consumers' acceptance of the pasteurization of milk. As health advocates, they need to fill that role again in the adoption of food irradiation. It is important for physicians and other health professionals to be able to answer patients' questions accurately regarding the irradiation of food; to recommend irradiated foods, particularly for immunocompromised people, pregnant women, children, and the elderly; to encourage local and state medical professional organizations to endorse the use of irradiated products; to encourage grocers to stock irradiated foods; and to support the use of irradiated beef in school lunch programs.
Dr. Osterholm reports that in his role as director of the Center for Infectious Disease Research and Policy he has received unrestricted grant support from Robins, Kaplan, Miller & Ciresi; the Foundation for Education, Public Health, and Social Justice; the United Health Foundation; the 3M Foundation; SureBeam; Ecolab; and Ion Beam Applications.
Source Information
From the Center for Infectious Disease Research and Policy (M.T.O., A.P.N.) and the School of Public Health, University of Minnesota (M.T.O.) — both in Minneapolis.
References
Mead PS, Slutsker L, Dietz V, et al. Food-related illness and death in the United States. Emerg Infect Dis 1999;5:607-625.
Foodborne Outbreak Response and Surveillance Unit. 2000 Foodborne diseases outbreaks due to bacterial etiologies. (Accessed April 8, 2004, at http://www.cdc.gov/foodborneoutbreaks/us_outb/fbo2000/bacterial00.htm.)
Food Safety and Inspection Service. 2003 Recall cases. (Accessed April 8, 2004, at http://www.fsis.usda.gov/OA/recalls/rec_actv.htm#2003.)
Food irradiation: available research indicates that benefits outweigh risks. Washington, D.C.: General Accounting Office, August 2000. (GAO/RCED-00-217.)
Loaharanu P. Irradiated foods. 5th ed. rev. New York: American Council on Science and Health, May 2003.
Merriam-Webster online. (Accessed April 8, 2004, at http://www.merriam-webster.com.)
Dickson JS. Radiation inactivation of microorganisms. In: Molins RA, ed. Food irradiation: principles and applications. New York: John Wiley, 2001:23-36.
Molins RA. Irradiation of meats and poultry. In: Molins RA, ed. Food irradiation: principles and applications. New York: John Wiley, 2001:131-92.
Josephson ES. An historical review of food irradiation. J Food Saf 1983;5:161-89.
Revision of the opinion of the Scientific Committee on Food on the irradiation of food. Brussels: European Commission, April 4, 2003. (Accessed April 8, 2004, at http://europa.eu.int/comm/food/fs/sc/scf/out193_en.pdf.)
Wholesomeness of irradiated food: report of a joint FAO/IAEA/WHO Expert Committee. World Health Organ Tech Rep Ser 1981;659:1-34.
Diehl JF. Safety of irradiated foods. 2nd ed. New York: Marcel Dekker, 1995.
Satin M. Food irradiation: a guidebook. 2nd ed. Boca Raton, Fla.: CRC Press, 1996.
Farkas J. Irradiation as a method for decontaminating food: a review. Int J Food Microbiol 1998;44:189-204.
Diehl JF. Food irradiation — past, present and future. Radiat Phys Chem 2002;63:211-5.
Tauxe RV. Food safety and irradiation: protecting the public from foodborne infections. Emerg Infect Dis 2001;7:Suppl:516-521.
Thayer DW, Christopher JP, Campbell LA, et al. Toxicology studies of irradiation-sterilized chicken. J Food Prot 1987;50:278-288.
Molins RA, Motarjemi Y, K?sferstein FK. Irradiation: a critical control point in ensuring the microbiological safety of raw foods. Food Contr 2001;12:347-56.
de Bruyn IN. The application of high dose food irradiation in South Africa. Radiat Phys Chem 2000;57:223-5.
Giddings G. Commercial food irradiation in the United States. Radiat Phys Chem 1996;48:364-5.
Crawford LM. Challenges and opportunities for food irradiation in the 21st century. In: Loaharanu P, Thomas P, eds. Irradiation for food safety and quality. Lancaster, Pa.: Technomic Publishing, 2001:9-16.
Food loss prevention in perishable crops. Agricultural services bulletin no. 43. Rome: Food and Agriculture Organization of the United Nations, 1981. (Accessed April 8, 2004, at http://www.fao.org/docrep/s8620e/s8620e00.htm.)
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