damage may be anticipated. Therefore, most surviving casualties will not have the severe injuries that result from the direct compressive effects of the blast wave.
Secondary blast injuries are caused by collapsing buildings and by timber and other debris flung about by the blast. Persons may also be hurled against stationary objects or thrown to the ground by the high winds accompanying the explosions. The injuries sustained are thus similar to those due to a mechanical accident: bruises, concussions, cuts, fractures, and internal injuries.
At sea, the shock wave accompanying an underwater burst will produce various mechanical injuries. These injuries will resemble those caused aboard ship by more conventional underwater weapons, such as noncontact mines and depth charges, but instead of being localized, they will extend over the entire vessel.
Equipment, furniture, gas cylinders, boxes, and similar gear, when not well secured, can act as missiles and cause many injuries.
A weapon detonated as an air burst may produce more burn casualties than blast or ionizing radiation casualties. Burns due to a nuclear explosion can also be divided into two classes: direct and indirect burns. Direct burns (usually called flash burns) are the result of thermal (infrared) radiation emanating from a nuclear explosion, while indirect burns result from fires caused by the explosion. Biologically, they are similar to any other burn and are treated in the same manner.
Since all radiation travels in a straight line from its source, flash burns are sharply limited to those areas of the skin facing the center of the explosion. Furthermore, clothing will protect the skin to some degree unless the individual is so close to the center of the explosion that the cloth is ignited spontaneously by heat. Although light colors will absorb heat to a lesser degree than dark colors, the thickness, air layers, and types of clothing (wool is better than cotton) are far more important for protection than the color of the material.
In addition to injuries to the skin, the eyes may also be affected by thermal radiation. If people are looking in the general direction of a nuclear detonation, they may be flash blinded. This blindness may persist for 20 to 30 minutes.
A second and very serious type of eye injury may also occur. If people are looking directly at the fireball of a nuclear explosion, they may receive a retinal flash burn similar to the burn that occurs on exposed skin. Unfortunately, when the burn heals, the destroyed retinal tissue is replaced by scar tissue that has no light perception capability, and the victims will have scotomas, blind or partially blind areas in the visual field. In severe cases, the net result may be permanent blindness. The effective range for eye injuries from the flash may extend for many miles when a weapon is detonated as an air burst. This effective range is far greater at night when the pupils are dilated, thereby permitting a greater amount of light to enter the eye.
Radioactivity may be defined as the spontaneous and instantaneous decomposition of the nucleus of an unstable atom with the accompanying emission of a particle, a gamma ray, or both. The actual particles and rays involved in the production of radiation injuries are the alpha and beta particles, the neutron, and the gamma ray. These particles and rays produce their effect by ionizing the chemical compounds that make up the living cell. If enough of these particles or rays disrupt a sufficient number of molecules within the cell, the cell will not be able to carry on its normal functions and will die.
Alpha particles are emitted from the nucleus of some radioactive elements. Alpha particles are helium nuclei of nuclear origin having an atomic mass number of four and an electrical charge of two positive. Because of this charge, alpha particles produce a high degree of ionization when passing through air or tissue. Also, due to their large size and electrical charge, they are rapidly stopped or absorbed by a few inches of air, a sheet of paper, or the superficial layers of skin. Therefore, alpha particles do not constitute a major external radiation hazard. However, because of their great ionization power, they constitute a serious hazard when taken into the body through ingestion, inhalation, or an open wound.
Beta particles are electrons of nuclear origin. They have a mass of approximately 1/2,000 of a hydrogen atom and an electrical charge of minus one. The penetration ability of a beta particle is greater than an alpha particle, but it will only penetrate a few millimeters of tissue and will most probably be shielded out by clothing. Therefore, beta particles, like alpha particles, do not