Nuclear war: the medical facts.

Abstract

This is the first of four articles describing the physical, biological, and psychological consequences of nuclear explosions. Any prediction of the effects depends critically on what military strategists call the scenario?how many nuclear weapons might be used, how quickly, where they will fall, and at what height they may be detonated. Though we have used a range of possible examples to illustrate specific effects, we make no attempt to predict the numbers or types of weapons that might be used in any future war. Every major war this century con? founded the military experts by turning out quite contrary to their expectations. First and foremost, atomic weapons cause explosions. Some of the effects of a nuclear explosion are comparable to those of a conventional (chemical) explosion: the major differences are the possible magnitude of nuclear explosions?they can be much bigger?and the release of harmful nuclear radiation. Almost all the early deaths and destruction caused by nuclear weapons are due to blast and heat?because most people close enough to the centre of the explosion to receive a potentially lethal dose of the extremely harmful initial radiation will probably have been killed or fatally injured by the explosion itself. The atomic bomb dropped on Hiroshima on 6 August 1945 had a power equivalent to 12 500 tons of conventional explosive, TNT. It was exploded in the air 500 yards above the ground and killed about 65 000 people either immediately or within a few weeks. Modern strategic nuclear weapons are more powerful. A one megaton bomb is equivalent to 1 000 000 tons of TNT; the total stock of nuclear weapons held by the United States and the USSR is estimated at around 10 000 megatons?equivalent to around 800 000 bombs of the Hiroshima size. The effect of a one-megaton explosion depends on whether it is exploded high in the air or close to the ground (fig 1). An explo? sion near enough to the ground to suck earth and building debris up into the stem of the mushroom cloud is known as a surface burst. Explosions high in the atmosphere?air bursts?do not produce this debris-filled mushroom. Regardless of height of burst, about 85% of the explosive energy of a nuclear fission weapon results in blast and heat. The remainder is produced as nuclear radiation?5% initial (produced in a minute or so) and 10% as residual radiation emitted over a period of time. An airburst at a height of 2000 yards produces an immensely hot, luminous fireball and a blast wave travelling at supersonic speed. When this wave hits the ground it is reflected, causing a secondary shock wave. These two waves fuse a little over one mile from the point vertically beneath the explosion (ground zero). The blast wave creates the greatest pressures around ground zero; as it travels outwards it gradually slows down and loses its force. Ten seconds after the explosion the shock wave is