Overexposure to these radiations, can alter the DNA of animals by the ionizing effect, it produces. If the rate of ionization is significantly large, it can result in permanent damage of the tissues. Sunburn, melanoma or different types of cancers are caused by overexposure to nuclear radiations from the Sun or nuclear tragedies. Kinetic energy released due to the highly penetrating shock waves generated by a nuclear explosion or the use of nuclear weapons, triggers a thermal radiation. Burns, are the most immediate and primary effects of these radiations.
Thermal radiation is approximately 35-45% of the total energy released in a nuclear explosion or test. This is a sufficiently large quantity, to permanently alter the gene structure and introduce hereditary problems, as is evident from the bombings of Hiroshima and Nagasaki. The subsequent generations were found to have several abnormalities. There is a parameter called radiation absorbed dose (rad), that gives an idea about the effects of radiation that bombards a human body. 50 to 150 rad causes alterations in the blood with symptoms like nausea, fatigue and vomiting. In case of exposure between 150-1100 rad amount, if not treated immediately, a victim may die in 30 days. For all levels above this, the central nervous system of the body fails, and loses control over all bodily functions, and death may occur in matter of few days or even hours.