Effects of low level ionising radiations.
Like non-ioni s ing e lectro-magnetic radiati on, the ionising radi ation is an essenti a l part of our li fe. Not only is it present in our surroundings but its presence within our body makes it an inseparable component of li ving. An average pe rson of about 60 kg body weight continuously e mits around 24,000 gamma rays photons e very minute whi ch ari se primarily from the radi oisotope of potass ium, [4oK] with natural abundance of 0.12% of natural potassium' ·2. From birth to death we are continuously getting exposed to gamma radi ation from within and from all objects outside name ly the building we live in , the earth , the cosmic radiations, radon in air and the food we eat a ll contain measurable levels of radio isotopes of potass ium, uranium, thorium and lead ' . The average radi ati on dose we get from natural sources of radiati on is between I and 2 mS v/year. T he exception is a fe w areas, notabl y, a coas tal strip in Kerala where the thorium depos its in the earth enhance the level of exposure to the people living in the region. Areas of high background natural exposure are li sted in Table 1.0n the other extreme is the nuc lear holocaust in Hiroshima and Nagasaki instantl y killing a large number of people and leav ing many survivors with radiation effects. Within these two extremes lies the region of low level exposure where the benefit s (primaril y medical) exceed the probab ility of harm .