June 1997
WASHINGTON, D.C. — Dramatic changes in the epidemiology of foodborne diseases are raising concerns from health officials and the scientific community who are demanding new methods to protect the food supply from bacteria, parasites and viruses.
The sporadic outbreaks involving Escherichia coli O157:H7 and Salmonella in red meat and poultry in the west, as well as the recent hepatitis A outbreak from strawberries, have convinced many scientists that the only alternative to ensure food safety is for the government to sanction the widespread use of irradiation on all domestic and across-the-border foods.
"These recent outbreaks will only increase if steps are not taken now to protect the food supply," said Michael T. Osterholm, PhD, MPH, state epidemiologist for the Minnesota Department of Health. "Terminal pasteurization, including the use of irradiation, will be necessary on a wide-scale basis if we are to realize a safer food supply in the United States."
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Osterholm explained that food irradiation is a process in which gamma rays, x-rays or electrons are used to disinfect, preserve or sterilize food. The most common source used in irradiation is cobalt-60, a radioactive isotope that emits gamma rays as it decays. In the irradiation process, food packed in crates or boxes are placed on conveyer belts and moved into the irradiator, where they are exposed to the radioactive source. High energy waves pass through the food, exciting the electrons in both the food and any pathogens that are present. When the electrons absorb enough energy, they break away from their atoms, disruption of the food's molecular structure then kills or reduces the number of bacteria, parasites, insects and larvae still lurking inside.
"In addition to killing off parasites, [irradiation] can also extend the shelf life of the food product," Osterholm said. "But there is no single solution to the problem of food safety; it does not replace good manufacturing practices on the part of food distributors and handlers."
According to Osterholm, the primary factors in the increasing problem of food-borne diseases are the combination of changes in the American diet and the changing commercial sources for these new food products.
"The price of farm labor and land costs are driving the fruit and vegetable industry out of America and across the border to the developing countries," Osterholm said.
The demand for fresh fruits and vegetables as part of a healthy diet has also caused changes in the production and distribution of those items. More than 75% of fresh fruits and vegetables are harvested outside of America's borders, particularly from developing countries like Mexico and Guatemala, and then delivered within days to American grocery stores and restaurants. These are when consumed in those developing countries, pose an increased risk of traveler's diarrhea. Also, on any given day, there are more than 400 types of fresh fruits and vegetables on sale in supermarkets and local grocery stores across the country, Osterholm said.
"We are documenting increased outbreaks that have taken on truly global dimensions," Osterholm said. "They involve numerous parasitic pathogens associated with the widespread distribution of fresh fruit and vegetables and there is little the consumer can do to protect him or herself since washing food has been shown to fail in eliminating all the bacteria on the food."
His view was echoed by Daniel L. Engeljohn, PhD, chief of the Standards Development Branch of the U.S. Department of Agriculture (USDA). However, Engeljohn added that it is important for irradiated products to be properly labeled as being irradiated so consumers can make educated choices in food-purchasing decisions.
"This is not a replacement for good [food] manufacturing practices," Engeljohn said recently. "Food distributors and sellers must also make efforts assuring that their products are bacteria-free and handled properly if we are to avoid problems in the future."
In a report released by the USDA, officials found that six foodborne pathogens — Salmonella, Campylobacter, E. coli 0157:H7, Listeria, Staphylococcus, and Clostridium — are responsible for an estimated 6.5 million to 33 million cases of human illness and up to 9,000 deaths in this country each year. The economic costs in sick days and loss of productivity due to these bacteria are estimated at between $9.3 billion and $12.9 billion annually.
Recently, the Food and Drug Administration (FDA) was petitioned to expand irradiation treatments to several freshly chilled/refrigerated red meat products not currently treated. Irradiation is already approved for limited use in controlling Trichinella spiralis in pork carcasses, for microbial disinfection of dry or dehydrated aromatic vegetable seasonings, for control of foodborne pathogens in fresh or frozen, uncooked poultry products and for sterilizing frozen, packaged meats used in the NASA space flight programs.
Joseph Madden, PhD, strategic manager for microbiology at the FDA's Center for Food Safety and Applied Nutrition said the FDA reviews these petitions to determine the efficacy of the radiation source in eliminating microbial pathogens. Madden said the FDA must also consider the effects irradiation may have on altering the nutritional content of the product being treated.
"Irradiation is the fourth leg on the American food table," said Madden. "Only three legs are in place right now — pasteurization, chlorination and immunization — without that fourth leg, we feel America's food table is not yet set."
For more information:
- Buzby JC, Roberts T. Bacteria and foodborne disease-medical costs and productivity losses. USDA. Agricultural Economic Report #741. August 1996.
- Madden, JM. FDA perspective on food irradiation. Presented at the National Foundation for Infectious Diseases Second Annual Conference. April 1997. Washington, DC.
- Osterholm, MT. Protecting America's food supply from microbial contamination: the role of irradiation. Delivered at the National Foundation for Infectious Diseases Second Annual Conference. April 1997. Washington, DC.
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