In 1948 the UN introduced a new category called Weapons of Mass Destruction: atomic explosives, radioactive material weapons, chemical and biological weapons.

Nuclear weapons

Hiroshima and Nagasaki demonstrated the devastation that nuclear weapons cause. Consequently, countries have always been unwilling to sell nuclear arms to the same extent as other weapons.

From the 1960s international agreements have been made to try to stop nuclear arms spreading. However, there are reports of uranium, missile technology and scientists illegally moving to states seeking to develop nuclear weapons.

This has been a grave concern particularly since the former Soviet Union's huge nuclear arsenal recently became so poorly guarded and funded.

Another problem is that much of the equipment needed to make weapons is also used for peaceful projects. This is known as dual-use. For instance, during the 1960s, Canada supplied reactors for Pakistan's nuclear power stations and the US did likewise for India. Both countries used the reactors to develop nuclear weaponry as well as generating electricity.

Because of heightened fears around selling nuclear arms technology it is thought a prosperous black market exists, involving smuggling fissile materials from the former Soviet Union. In 1994, Czech authorities seized three kilograms of Highly Enriched Uranium. In the same year 400 grams of weaponsgrade plutonium were seized by police in Germany. Just two years ago, nuclear weapons telemetrics equipment was captured by officials at a Budapest airport. According to the Oxford Research Group: “these smuggling incidents...are almost certainly the tip of the iceberg.”

Because of strict controls there is little legal nuclear arms trading. Any sale of technology tends to be secret and illegal. (Unless it is US arms companies selling Trident missiles to the British government.) Nuclear arms sales therefore make up a tiny fraction of the arms trade. But any sale of technology has the potential to destroy thousands, if not millions, of people.

Chemical and biological

Chemical and biological weapons (CBW) are almost impossible to trace within the arms trade because they can be made from products such as day-to-day cleaning fluids.

CBW are hardly a modern device of warfare. The ancient Assyrians and Persians poisoned drinking water. The Romans used choking smoke. In the fourteenth century an army besieging the Crimean port of Kaffa catapulted plague-infected human bodies over the city walls.

In the First World War the French used tear gas. Later Germany used chlorine; a choking green-coloured gas. Chlorine was readily available as a low-cost industrial product and is more commonly used as a cleaning fluid - especially in swimming pools.

Soon attacks became easy to avoid with the introduction of gas masks. This inspired more lethal inventions such as Tabun and Mustard Gas (first developed in Germany) and VX, a nerve agent designed in Britain during the 1950s. Later, scandals erupted in Germany as their companies, innocently they argued, provided Iraq with chemicals it was able to turn lethally against Iran and Kurdish communities in the 1980s.

At least twenty states have chemical and biological weapons programmes. Russia reportedly holds the largest stock in these types of weapons.

It is very difficult to stop exporting products such as chlorine or flyspray to every country on earth. This part of the arms trade, more than any other, demonstrates the difficulty we face in establishing how the equipment we export will be used abroad.