CBR agents have become a focus of counterterrorism efforts because they possess a number of characteristics that would seem to make them attractive to terrorists. Dispersed via the air-handling system of a large public building, for example, a very small quantity of a CBR agent may produce as many casualties as a large truck full of conventional explosives, making the acquisition, storage, and transport of a powerful weapon much more feasible. Although not as easy to acquire or make as some have suggested, serviceable CBR weapons are within the intellectual, financial, and technological reach of many groups and individuals. Some CBR agents can be delivered very effectively as “invisible killers,” that is, as colorless, odorless, and tasteless aerosols or gases, enhancing their psychological impacts and making it difficult to locate and identify the source. Some if not all CBR agents are also long-lasting threats. That is, contaminated victims of attacks with chemical, radiological, and some biological agents can spread the agent to others far from the scene of the initial release, and some infectious biological agents will ultimately transform the victims into carriers who can transmit the agent themselves. Lastly, the biological and radiological agents and some of the chemical agents of concern produce their deleterious effects only after delays of hours to days or weeks after exposure, facilitating the escape of the perpetrator and making detection of the attack difficult for both healthcare providers and law enforcement officials.
There are thousands of chemicals that at some dose may result in morbidity or mortality for humans. In the present context, “chemical agents” generally comprise a relatively short list of chemicals that at some time have been “weaponized” for military use. Some of these agents have no nonmilitary use (e.g., nerve agents and mustard gas); other agents such as chlorine and ammonia are widely used by industry. These agents are often classified by the site or nature of their effects in humans, such as nerve agents, blister agents, choking agents, vomiting agents, incapacitants, and tear agents; and many of these agents are not well known by civilian hazardous materials technicians and other emergency responders, medical personnel, or law enforcement officials. Even common industrial chemicals may be difficult to identify without specialized equipment when they are encountered in an unfamiliar context. The agents in Table 1-1 have been the primary focus of efforts to prepare for chemical terrorism, in part because of their toxicities but to a greater extent because of the health care community’s unfamiliarity with these agents.