In the aftermath of the World Trade Centre tragedy, the focus of the international community has turned to the threat of chemical or biological terrorist attack. The World Health Organisation has warned governments to be on the alert for such attacks and two anthrax cases in Florida are being investigated by the FBI for any terrorist links.
For the civilian population, the very mention of chemical and biological warfare provokes fear and uncertainty. Chemical and biological weapons are intended to have both a physical and psychological impact on the target population.
The use of these weapons belongs to the sphere of non-conventional military operations known as nuclear, biological and chemical (NBC) warfare.
In the case of nuclear warfare, the list of states that possess nuclear weapons has increased in recent years. These weapons systems must have the capability to deliver a nuclear payload to a specific target well beyond a nation's boundaries. At present, such weapons systems are beyond the reach of terrorist groups.
Despite this, it is believed within the international intelligence community that the potential now exists for terrorist groups to acquire nuclear devices. One risk has come from the break-up the former Soviet Union and the uncontrolled disposal of its nuclear assets. In the absence of a sophisticated delivery system, it would be necessary for the terrorist to courier such a device into a major population centre for detonation. It is now beyond doubt that the fanaticism and suicidal intent for such an attack exists. Western military analysts therefore consider such an attack an emerging and serious threat.
However, for technical and security reasons, such an attack would be a difficult operation to mount and execute successfully. In terms of a weapon of mass destruction, for the terrorist, chemical and biological weapons rank as a more viable option.
At present, chemical weapons are widely available in those countries identified by the US as being under suspicion of "harbouring" terrorist networks including Iran, Iraq, Sudan, Syria and Libya. Chemical weapons consist of a number of major categories. These include nerve, blood, choking, blister and psychochemical agents. They come in gas, aerosol or liquid form. They can be persistent or non-persistent, depending on the intentions of the attacker. It is possible to deliver chemical weapons that will destroy the human population, leaving buildings and infrastructure uncontaminated for later use. Persistent agents would be intended to remain in the environment as a contaminant thereby "denying ground" to the enemy or target population.
Nerve agents target the human enzyme cholinesterase, leading to the disruption of muscle function. This causes seizures and evntually death. Nerve agents include Tabun, Sarin and Soman.
Blood agents interfere with the interchange of oxygen within the circulation system. By inhibiting this process, the victim "drowns" in his/her own blood supply. Such agents include hydrogen cyanide and cyanogen chloride. Choking agents affect the respiratory system, targeting the nose, lungs and throat. This causes pulmonary oedema and death. Choking agents include phosgene and chlorine. Blister agents are absorbed through the body's largest organ, the skin, causing extensive burns and blistering. Psychochemical incapacitants such as quidnuclidynil benzilate cause hallucinations and act as a depressant to the central nervous system. All of the above-mentioned nerve agents act on contact with the skin, by ingestion or inhalation and are designed to wound, incapacitate and kill. In terms of their efficacy, they compare favourably with nuclear weapons. According to recent figures, they also compare favourably in cost. For example, to neutralise one square kilometre of a target area with nuclear weapons would cost approximately $800 (about £690). To complete the same task with conventional weapons, (such as high explosives) would cost in the region of $2,000. To do so with chemical weapons would cost a mere $600. They are also relatively cheap to acquire. From the point of view of viability, efficiency, physical and psychological impact, chemical weapons represent an attractive package for the terrorist organisation.
Even more tempting for the terrorist however, is the option of biological weapons. In terms of raw materials, it would be possible to neutralise one square kilometre of a given target area with biological agent for as little as $1. Biological weapons consist of viral and bacterial agents. Viral agents require a living cell in order to function and cause such epidemics as smallpox, flu and yellow fever. Viruses cannot be treated by antibiotics. Bacterial agents consist of single-cell micro organisms capable of growing and reproducing themselves. They cause such epidemics as cholera, plague, tularemia and anthrax - the cause of the latest scare in the US. Unlike viral agents, bacterial agents can be treated by antibiotics, provided they are detected early enough.
A terrorist attack on the west, involving chemical and/or biological agents, is thus a threat. As is the case with nuclear weapons, the challenge facing the terrorist is in the delivery and dispersal of such agents. In the absence of conventional artillery or missiles as a means of delivery, the terrorist will rely on alternative means. Such means would have included the option of aerial dispersal by aircraft. This option would now appear to be closed in the wake of the US ban on crop dusting in North America. For Europeans, the main threat would most likely be in the form of a terrorist or terrorists acting as a human courier for chemical or biological agents.
In terms of the means of dispersal, the terrorist could target vulnerable areas in the food chain such as sites for the mass distribution of food products, or water supplies. Likely targets would be large multi-storey air-conditioned buildings - of the kind where the US investigation is under way - or enclosed spaces such as shopping malls, the underground or metro. As was the case with the World Trade Centre, the targets would be carefully selected with maximum symbolic and material damage being the aim. Like the World Trade Centre attack, these attacks would likely be one-off terrorist "spectaculars".
All of these factors point to high-profile targets in the US, continental Europe or Britain.
Dr Tom Clonan is a former Army Captain with 12 years service in the Defence Forces. He now lectures in the Political Economy of Communications in the Institute of Technology, Tallaght, specialising in communications, media and defence issues.