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Reopening Public Facilities after a Biological Attack: A Decision Making Framework
tions regarding safety—is instructive in the need for transparency in public health matters that arise against a national security backdrop.
MICROBIAL DECONTAMINATION IN FOOD AND WATER SUPPLIES
Foodborne and waterborne infections are commonplace examples of the need to reduce pathogen occurrence in environments that have a direct effect on human health. Microbial risk assessment, addressed in greater detail in Chapter 4, is a useful tool for setting standards in food and water safety, making it appropriate for use in the current application.
The first direct use of microbial-risk-based criteria for regulating exposure to pathogens in the United States was in the U.S. Environmental Protection Agency ( EPA) water quality criteria for recreational waters (EPA, 1986a). That document listed water quality limits that were set so that a risk (from recreational contact such as swimming) of 0.008 illnesses/bather-day (for fresh water) to 0.019 illnesses/bather-day (for marine water) per exposure resulted; experts deemed that an acceptable risk to the public (EPA, 1986a).
Shortly thereafter, the Surface Water Treatment Rule mandated that all water purveyors that used surface water introduce treatment sufficient to provide adequate control of pathogens. In the rule’s development, treatment was to achieve a residual risk of infection of less than 1/10,000 per year based on microbial risk assessment, even if there was a high concentration of pathogens in raw water (Macler and Regli, 1993).
In food safety, canning, the first large-scale method of industrial food preservation, relies on heat to minimize risk from pathogens and to reduce spoilage. A criterion that is sufficient to provide 12 logs of inactivation (that is, only one out of 1 × 1012 spores would remain active) of Clostridium botulinum spore—referred to as a “botulinum cook”—is commonly applied even though the criterion does not necessarily result in a sterile product (Farkas, 1997). More recent concerns on food safety—particularly for less thoroughly processed foods—have led to increasing attention to providing a scientific basis for food safety criteria.
A committee of the Institute of Medicine (IOM, 2003) has examined food safety. Among its conclusions are two that are germane to the current report:
There is a need to define “acceptable levels” of hazard reduction at critical points linked to public health objectives. The Food Safety Objective concept can help establish this link and define these levels, and it can also provide a theoretical framework to relate performance standards to public health objectives.
Quantitative microbial risk assessment offers the scientific tools to define the most effective solutions for lowering consumer exposure to foodborne microbial hazards.