rapidly in the last three decades that one can imagine rational programs leading to quite new toxic activities.
Industrial Chemicals and Derivatives of Them. For terrorist use, industrial chemicals (e.g., chlorine, phosgene, hydrogen peroxide, hydrofluoric acid) might be attractive since they are widely available, and are often shipped thorough, or in the vicinity, of cities in tank car or tank truck quantities. Although such shipments are easy to track in the developed world, they are not in the developing world, and can be adapted as weapons (as ammonium nitrate—a common fertilizer, has been adapted as an explosive). In open spaces these chemicals tend to dissipate by mixing with the atmosphere; in enclosed spaces they are more effective.
Weapons for Use by Terrorists. Chemical weapons are very well suited for attacks in which the target is a “soft” biological target in an enclosed space (e.g., commuters in a subway or bus, children in schools, passengers in airplanes). HCN, H2S are both readily prepared, and quite capable of causing a significant number of casualties. These compounds could be used to disrupt transportation systems. Benzene and carbon tetrachloride are readily available, and although not very toxic on single exposure, potential tools to cause panic since both are known to cause cancer; aflatoxin is a fungal product which is a very potent carcinogen.
Biological Toxin Weapons. Biology produces a number of very toxic molecules (botulism toxin, ricin, many others: for example, peptides that alter mood, or produce fear, or interfere with judgment or memory or immune function or reproductive performance). These compounds are not volatile, and would probably have to be delivered in an aerosol. The technology of biological toxins is sophisticated, but well understood. An important feature of these materials is that the onset of symptoms can sometimes be delayed, so warning through development of symptoms may not happen until well after delivery of a complete dose. They also have the property that they fall “between” chemical and biological weapons, and are thus ambiguous in who is responsible for them.
Cost Effectiveness. Chemical weapons have the potential to be effective in confined spaces, particularly when the primary objective is to cause disruption rather than large number of casualties. They are, therefore, effective as weapons in terrorism and insurgency, and against specific, localized, military targets; they
Committee on Determining Core Capabilities in Chemical and Biological Defense Research and Development, Board on Chemical Sciences and Technology, Division on Earth and Life Studies, National Research Council "
Appendix B: Additional Thoughts on the Nature of the Chemical Threat ."
Determining Core Capabilities in Chemical and Biological Defense Science and Technology . Washington, DC: The National Academies Press,