Reopening Public Facilities After a Biological Attack A Decision Making Framework (2005) / Chapter Skim
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8 Analyzing Health Risks
8 Analyzing Health Risks
Pages 105-119
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From page 105... ...
of microorganisms. Illness attendant to exposure to chemical agents, even at low doses, involves exposure to substantially larger numbers of molecules (thousands or more)
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From page 106... ...
+ 1 o g2nism / / \ AX · +2 organisms f \~` V z _100 92m2ms .01% - / 0.01 0.1 1 10 Number of Organisms inhaled by Average Person 100 the form of specific disease in specific subgroups of the human population (Rubin, 1987) , whereas many particles of a chemical agent would be necessary to provoke an effect depending on the chemical agent and the mode of action In the case of microbial agents, an ingested, inhaled, or absorbed microorganism can multiply within the body of a susceptible human, to produce sufficient microorganisms in viva that illness can result.
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From page 107... ...
Those terms also are called the "median infectious dose" or "median lethal dose." Unfortunately, summary tabulations of infectious agents often use the terms "infectious dose" or "lethal dose," without modifying adjectives. The result has been the misapprehension that doses below the ID50 and LD50 are without adverse effect.
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From page 108... ...
or the survival probability distribution (in the case of the beta-Poisson) accounts for all factors, including host immunity, that act as forces to reduce the ability of a retained organism to successfully colonize to the extent necessary to induce infection or disease.
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From page 109... ...
Relative Susceptibility of Different Subpopulations in Risk Analysis As a matter of public policy, the guidelines for safe reoccupation of facilities contaminated with harmful biological agents should protect not only the general population but also sensitive or susceptible subpopulations. However, what conshtutes more susceptible has not been rigorously defined.
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From page 110... ...
There could remain umesolvable uncertainties about which of the particular modifiers might be most appropnate, especially where good animal models are lacking for an agent. "Thresholds" for Microbial Dose-Response Analysis In assessing risks attributable to exposure to microorganisms, it has frequently been asserted that there exists a threshold (minimum infectious dose)
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From page 111... ...
The same set of assumptions underlies the dose-response relationship used for assessing nsk attributable to animal or human exposure to pathogens. Therefore, long-standing observations on microbial behavior have supported the use of population doseresponse models without a threshold; that is, a dose below which no nsk to a population exists (or a nonzero intercept on the dose scale)
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From page 112... ...
Although the nonthreshold model implies that there is no threshold below which an agent poses zero nsk, it indicates that the probability of infection is extremely low. In contrast, a threshold model implies a definitive threshold below which no infection would occur.
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From page 113... ...
The available data on infectious organisms are inconsistent with dose response relationships that have steeper slopes than the nonthreshold models at the median, and therefore the concept of a threshold is not supported by available data. Determination of Cleanup The determination of the amount of cleanup required, and the processes used to achieve it, must consider both quantitative (risk assessment)
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From page 114... ...
Each has a specific uncertainty and variability, so the final estimate of surface and air concentrations corresponding to the nsk level (or, conversely, the risk resulting from a given set of surface and air concentrations) itself has a certain confidence distribution.
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From page 115... ...
Nonthreshold dose response models present a more cautious approach that has been found appropriate for describing human response to a diversity of infechous agents via ingestion, inhalation, and other routes of exposure. Dose response data for most of the pathogens of concern (biological agents)
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From page 117... ...
Finding 8-2 Because minimal publicly available data exist on which to base human dose response relationships for the critical pathogens, animal data must be used.
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From page 118... ...
Risk Analysis 22(2)
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From page 119... ...
. Dose Response Relationships for Gastmintestmal Padhogens in an Animal Model.
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