Chemical weapons may be used as overt agents in that the effects are
more apparent and occur much quicker than those caused by biological weapons of mass destruction. Chemical weapons are readily available and easily accessible which as a result can lead to major mortality and morbidity, causing panic and social disruption.
There are many chemical weapons including those that affect nerves (sarin, soman), and those that affect the components of the blood (cynanide), vesicants (lewiste, nitrogen and sulfur mustard, phosghene), heavy metals (lead, arsenic), volatile toxins (benzene, chloroform), pulmonary agents (chlorine), and corrosive acids (sulfuric acid, nitric acid). One of the most readily available chemical agents which terrorist groups who intend to use them as chemical weapons include chlorine, phosgene and cyanide since these agents are widely used in industrial plants and similar industries.
Volatility and Persistence of Chemical Weapons
Volatility is the tendency for a chemical weapon to become a vapor. The most volatile agents are phosgene and cyanide. Most of these chemicals are much heavier than atmospheric air, except for hydrogen cyanide. Therefore, in the presence of most chemicals, people should stand up and to avoid heavy exposure since the chemical will most likely be sinking toward the ground.
Persistence of a chemical agent when used as a weapon means that the chemical is less likely to vaporize and disperse since most known volatile chemicals don’t evaporate very fast. Most industrial chemicals are not very persistent. Weaponized agents (chemicals that are developed as weapons by the military or terrorist groups) are more likely than industrial chemicals to penetrate the mucous membrane and the skin which can lead to secondary exposure.
Toxicity and Latency of Chemical Weapons
Toxicity is the potential of a chemical agent to cause injury to the body. The median lethal dose (LD50) is the amount of the chemical agent that can cause death in approximately 50% of those who are exposed. The median effective dose (ED50) is the amount of the chemical that will cause signs and symptoms in 50% of those exposed to a potential toxic chemical agent. The concentration time (CT) is the concentration released which is multiplied by the time exposed (mg/min).
Latency is defined as the time from the time of absorption to the appearance of the initial signs and symptoms. For example, sulfur mustards and pulmonary agents are known to have the longest latency where as nerve agents, vesicants and cyanide produces visible clinical symptoms within seconds upon exposure.
Limiting exposure to chemical weapons
When a community becomes a target of a terrorist attack which uses chemical weapons to inflict damage and destruction of human life, it is imperative that evacuation from the site of exposure be the main priority of rescuers who responding to the site of the attack. Removal of a person’s clothing and decontamination as close to the scene as quickly as possible before transporting the victim/s to the nearest medical facility for further treatment and management. Soap and water are effective means of decontamination in most cases. Medical staff and personnel involved in decontamination efforts must wear personal protective equipment in containing and disposing of the runoff following decontamination procedures after a confirmed terror attack with the use of chemical weapons.