battlefield sensors and those for homeland defense. Established procedures, pre-engagement vaccination, and protective gear are well defined for the military battlefield scenario, but with the exception of some emergency response personnel, these are virtually nonexistent in the civilian sector. Further, military operations are generally conducted with the benefit of some intelligence data, giving some a priori specificity to the type of chemical, biological, or nuclear threat likely to be encountered. By contrast, terrorist use of weapons of mass destruction is less predictable. Finally, military operations may tolerate exposure levels that hurt but do not cripple unit effectiveness, whereas protection of the health of the civilian population to the maximum extent possible is a political mandate.

Nevertheless, sensors developed for battlefield detection of chemical, biological, and nuclear weapons represent a good starting point. But to meet the needs of homeland defense, it will be necessary to have sensors that provide the lowest achievable false-alarm rate, operate against the widest possible number of agents, and offer significantly improved sensitivity, specificity, and area coverage.

Because chemical, biological, and nuclear weapons each pose different threat scenarios, differences in sensors and their operational protocols must be considered.

Chemical weapons are point- or area-release, and their health impacts are generally seen immediately. However, they may be detectable before actual deployment. Trace amounts of chemical contaminant can be detected on the package containing the weapon and even on the individual transporting it. Current sensor capabilities are fairly limited; in many cases, the best “technology” for practical use continues to be trained dogs, which provide broad-spectrum high-sensitivity sensing. Manufactured sensors are often designed for use in specific environments and to be selective for only one or two chemicals. The development of new sensor systems for chemical agents will require advances in a number of different subsystems, including sample collection and processing, presentation of the chemicals to the sensor, sensor arrays with molecular recognition, sophisticated signal processing, and amplification of the transduction events. The precise chemical signals that provoke responses in dogs remain uncertain, and basic research to study how animal species accomplish both detection and identification of trace chemicals could yield new concepts for manufacturing better sensor systems. (See Chapter 4 for more on chemical sensors.)

Biological weapons can also be point- or area-release, but their health impacts may not become apparent for days or weeks. Further, it is problematic whether trace amounts of a biological agent will be discernible, so that the first opportunity to detect it may be at release. Thus the rapid diagnosis, treatment, and recognition of the weapon that caused the illness is very important. Equally important is the flow of rapid and reliable information throughout the health-care community, particularly in the early stages of recognition of a bioterrorist attack.

The classic means of surveillance of biological agents is to identify patients

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