Following the events of 11 September there is an emerging concern of terrorist use of chemical and biological weapons. There is a large assortment of chem-bio weapons with diverse characteristics that are suitable for terrorist use. There are many advantages in using these weapons rather than conventional arms and their disadvantages are quite insignificant; hence they could become a key element in the terrorist arsenal. 

The first distinct advantage of chem-bio weapons is the terrifying effects of using such weapons in the minds of common citizens. Second, a cost-benefit analysis reveals the difficulty of anti-terrorist groups detecting such weapons, and the low expense and expertise required to develop them. Chem-bio weapons have long been considered ‘the poor man’s atomic bomb’. The cost argument is supported by experts who contend that a large-scale operation against a potential  civilian target might cost $2,000 per square kilometer with conventional weapons, $800 with nuclear weapons, $600 with nerve-gas weapons, and a mere $1 with biological weapons. 

Like other weapons there are some disadvantages that the terrorists will encounter in the use of chem-bio weapons. Due to their nature, the use of chem-bio weapons could have two repercussions. The first would be retaliation by anti-terrorist squads, and the second is that it could damage the image of the terrorist groups, unless these groups are not concerned about their image and the collateral damage caused. Following such an assessment terrorist groups are likely to renew their efforts to procure and eventually use chem-bio weapons. After getting these agents the terrorists would have to determine how they can disperse the agent effectively, given the potential risk it poses to those who handle it.

The choice of lethal chemical agents is large. There are several approaches to classifying them but the most useful is to group them by their effects: blister agents, blood agents, choking agents, and nerve agents.  Blister agents are intended to ‘cause incapacitation rather than death’. These agents were used during World War I and their use by a terrorist group depends on the objectives of the group.  Mustard gas, Nitrogen Mustard, Phosgene Oxime and Ethyldichloroarsine (ED) are examples of blister agents. Cyanide based compounds are the key components of blood agents. Hydrogen Cyanide (HC) is a blood agent that has a lethal dose, which is slightly higher than that of phosgene, but is less effective due to its rapid rate of evaporation. Other agents are Arsine (SA), Cyanogen Chloride (CK), and Hydrogen Chloride. Choking agents were used during World War I and also in Nazi concentration camps. With the advent of nerve agents they have lost much of their value. These substances can cause death and their greatest danger arises from is their easy availability. Phosgene, Chlorine, Diphosgene (DP), Nitrogen Oxide and Perflurorisobutylene (PHIB) are examples of choking agents. The recent developments in chemical weapons has been in nerve agents. Its latest use by a non-state actor was at the 1995Tokyo subway attack by the Aum Shinrikyo using Sarin. Nerve Cyclohexyl Sarin (GF), Sarin (GB), Soman (GD) and Tabun (GA) are other nerve agents.   These chemicals are difficult to obtain. 

The Geneva Protocol 1925 and the Chemical Weapons Convention (CWC) of 1993 (entered into force 1997) are the only international instruments that govern chemical weapons. Presently 174 states have signed the CWC or acceded to it, while 143 States have deposited instruments of ratification or accession. The CWC is the product of more than twenty years of negotiations at the Conference of Disarmament in Geneva. It is one of the most complex international conventions ever negotiated. It contains a Preamble, twenty-four Articles and three Annexes. It also incorporates a highly intrusive verification mechanism.