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A Framework for Assessing the Health Hazard Posed by Bioaerosols
ACPLA measurements, and also in anticipation of the possible discovery that the number of sites where aerosol particles deposit biologically active units in the respiratory tract may need to be known to predict health risk for some agents. BAPLADae would be measured in a manner similar to current methods for ACPLA, with the exception of employing a defined challenge aerosol particle size distribution and normalizing biological activity for each agent.
Recommendation B: In support of an overall Department of Defense DOD detectorevaluation philosophy that relates health risks and aerosol exposure, the committeerecommends using the relationship presented inFigure 3.1to provide a framework forrelating health hazards and aerosol exposure and to identify the information provided bydifferent types of detectors.
This relationship, described in greater detail in Chapter 3, provides a framework for evaluation of health risk presented by exposure to aerosolized biological warfare agents. Note that, though the physical and biological characteristics of a bioaerosol are the features evaluated by a detector, the data provided by that detector cannot be appropriately assessed without consideration of the physiological effect of exposure. In addition to those specific considerations, other factors contributing to predicting health risk can be inserted into the equation to aid in the development of appropriate requirements and response protocols.
Recommendation C: Standardize testing procedures for evaluating detectors.
C.1 Aerosol challenges need to be well characterized, includingDae, BAULADae,BAPLADae, and material rendered inactive during the process of aerosol dissemination andtransport.
C.2 Challenge biodetectors with aerosols of defined size distributions. At least three challenge aerosols with different median aerodynamic diameters (Dae) should be used in chamber or component testing of detectors. These should be chosen to represent deposition in the three regions (extrathoracic, tracheobronchial, and pulmonary) of the respiratory tract.
C.3 The standardized unit of hazard, BAULADae, and the broader evaluativeframework for health hazard should be adopted as DOD-wide standards, including use inT&E and procurement. The method for implementing the unit and framework should bedocumented, externally peer reviewed, and published. Revisions and updates should follow similar vetting processes so that calibration, referee instruments, and testing reagents are standardized and variation is identified.
To take full advantage of the benefits provided by the new unit of hazard and the health risk evaluation framework, the T&E protocol for detector evaluation must be standardized. A full review of the testing methodology is beyond the scope of this committee. However, some issues that were brought to light during the course of this study are noted here. This list should not be considered comprehensive, but is indicative of the potential value an in-depth review could provide. For example, as BAULADae is linked to biological activity, it will be necessary to prepare test samples consistently to ensure that the amount of active agent presented to the detector does not vary across tests. It is important to understand the effect that sample preparation, aerosolization, and cloud transport have on the aerosol particles. Generated biological aerosols will change with relative humidity and temperature. These changes must be addressed to have a consistent, comparative, and scientifically rigorous test and evaluation