that there is no induction of radiation in foods that are treated with isotope sources of ⁶⁰Co or ¹³⁷Cs, x-ray sources of up to 5 million electron volts (MeV), or accelerated electron beam sources of less than 10 MeV (Koch and Eisenhower, 1967; Becker, 1983). It should be noted, however, that irradiation is not a panacea. In dairy products, which contain lipids sensitive to oxidation, for example, taste is affected. Furthermore, the technique is generally considered much less effective for inactivating viruses, compared with its effectiveness with bacteria and other more complex pathogens (e.g., fungi).

There are several important, ongoing demographic changes in the United States that will have direct and indirect effects on the emergence of new food-borne microbial diseases. Foremost is the fact that, at least through the early twenty-first century, the population increasingly will be composed of the elderly, a group particularly susceptible to food-borne pathogens.

Population expansion and the accompanying demands on infrastructure can also affect the safety of the food supply. For example, when estuarine areas are developed for residential or recreational purposes, water treatment capacity often lags behind requirements imposed by the population increase. In some cases, potentially dangerous viral and bacterial pathogens are released into the water from sewage effluent and storm-drain runoff, where they are concentrated by shellfish and subsequently harvested and consumed, often with minimal processing. The closing of shellfish beds because of the presence of these pathogens has become a major public health and economic issue in a number of coastal regions. The problem is compounded by poaching from closed beds. Methods for testing water for human enteric viruses (e.g., hepatitis A and C, Norwalk virus, and caliciviruses) currently are inadequate (Institute of Medicine, 1991b).

In general, particularly in the developed world, the public expects its food supply to be safe. To a great extent this expectation has been met through the safe manufacturing and distribution of prepared foods. The extent of training that individuals receive in proper food handling and preparation is declining. Owing to changes in family structure and the roles of women, home economics courses are being deemphasized in schools, and the use of convenience foods and dining out is increasing. With these changes, assumptions about food safety may lead to complacency. Consumer inattention to appropriate steps for maintaining food safety in the home can easily overwhelm safeguards built into food production and processing.