Chemical Informatics

Among the Weapons of Mass Destruction, chemical warfare (CW) is probably one of the most brutal created by mankind in comparison with biological and nuclear warfare. Chemical weapons are inexpensive and are relatively easy to produce, even by small terrorist groups, to create mass casualties with small quantities. The characteristics of various CW agents, general information relevant to current physical as well as medical protection methods, detection equipment available and decontamination techniques are discussed in this review article. A brief note on Chemical Weapons Convention is also provided.

Keywords: Blister agents, chemical warfare, decontamination, detection, mustards, nerve agents, protection

Among the Weapons of Mass Destruction (WMD), chemical warfare (CW) is probably one of the most brutal created by mankind. CW agents are extremely toxic synthetic chemicals that can be dispersed as a gas, liquid or aerosol or as agents adsorbed to particles to become a powder. These CW agents have either lethal or incapacitating effects on humans.[1] They differ from explosive chemicals in which the destructive effects are caused by shear force and are localized. Thousands of toxic substances are known, but only some of them are considered as CW agents based on their characteristics, viz. high toxicity, imperceptibility to senses and rapidity of action after dissemination and persistency, and are listed as scheduled chemicals in the Chemical Weapons Convention (CWC).[2] According to the CWC, chemical weapons are defined as toxic chemicals and their precursors, munitions and devices, and any equipment specifically designed for use directly in connection with such weapons.

The use of poisonous chemicals from plant extracts to poison individuals is widely documented throughout the Middle Ages and Renaissance, but it was not until the expansion of industrial chemistry in the 19th century that mass production and deployment of CW agents in war became a possibility. Thus, the birth of modern CW was ushered in by the German gas attack with chlorine on 22nd April 1915 at Ypres, Belgium. The use of these toxic chemicals, including phosgene, sulfur mustard and lewisites caused 100,000 deaths and 1.2 million casualties in World War I (WWI).[3] Millions of innocent civilians were killed by the Nazis with Zyklon B gas (hydrogen cyanide gas) during World War II. Agent Orange – a defoliant – was used by the USA during the Vietnam War. The only major use of CW since WWI occurred during the Iran–Iraq War in the 1980s. The largest single CW attack killing around 5,000 people followed an Iraqi nerve agent attack on the Kurdish civilian population of Halabja. This attack illustrates the one single characteristic of CW agents that allows them to be considered as WMD.[4] This incident, together with the relative simplicity of their production, makes them an attractive terrorist weapon. This has been made particularly evident by the Sarin attacks by a Japanese cult in Matsumoto city (1994) and the Tokyo subway system (1995), causing 5,500 injuries and 12 deaths. The threat of using CW agents in domestic terrorist attack was demonstrated for the first time in these cases. However, mass casualties were prevented not as a consequence of the medical response but because of the inefficiency of the delivery method.[5] Subsequent investigations revealed that the sect had also produced Tabun, Soman, Vx and Botulinum toxin.[6] Thus, even small groups of individuals can use CW agents to create massive and extensive human suffering without any warning.

Terrorists have previously used more conventional means of violence, such as bombings, assassinations and hostage taking, to promote their causes. Terrorism and criminal activities achieved a whole new quality after incidents like the repeated assaults on the World Trade Center in New York culminating in its destruction on September 11, 2001 and the subsequent dissemination of anthrax-letters.[7] On April 6, 2004, news agencies reported that the British police foiled a plot by members of the El-Qaeda to prepare and detonate a bomb containing OsO4 in London.[8] Following these, over the last decade, it has been feared that terrorists might be tempted to acquire and use such weapons against innocent civilians. The major reasons for the production and use of such weapons are manifold. First, chemical weapons are cost-effective, particularly when used against concentrated forces or populations. Second, they may be used at lower levels of concentration with an aim to cause panic and disorder among civilians. Among the CW agents, chlorine, phosgene and cyanides are widely used in the manufacturing processes of various chemical or pharmaceutical industries. Thus, the act of terrorism might also occur in the form of a toxic chemical release, e.g. when such industrial plants, stocks or transports become a target of terrorist attacks.[9] In the Tokyo subway attack, a simple plastic bag containing the CW agent Sarin was kept on an underground train, allegedly piercing it with umbrella tips before the cult's escaped.[10] Therefore, intentional release of such agents during National or International events can be easily achieved by transporting them in the form of water bottles, cold drink cans, ampoules or even pens, etc. to the site. The effect of intentional release of CW agent varies greatly, depending on several factors, including the toxicity of the compound, its volatility and concentration, the route of exposure, the duration of the exposure and the environmental conditions. The release of such agents in an enclosed place could deliver doses high enough to injure or kill a large number of people, whereas in an open area, chemical cloud would become less concentrated as it spreads, leading possibly to numerous mild casualties.