Gamma-rays liberated from natural sources are predominantly owing to 238U and 232Th series elements and their descendants, as well as 40K and these rays are responsible for the cause of irradiation of human body which results in damaging the tissue and DNA to cause lung cancer. The assessment of these natural sources permits the quantization of the background baseline of natural radioactivity and assessment of the radiation hazard risks to an individual. As per the reports, the global mean of the effective dosage from the background natural radiation is 2.4 mSv y−1. Various regions of the world with high natural radiation levels (China, 5.4 mSvy−1; Kerala India 35 mSvy−1; Guarapari Brazil 35 mSvy−1; and Ramsar Iran 260 mSvy−1) and low radiation levels ((Denmark, 0.45 mSvy−1; USA, 0.88 mSvy−1; Japan, 1.26 mSvy−1; Austria, 1.34 mSvy−1; Ireland, 1.58 mSvy−1; Germany, 3.8 mSvy−1, respectively) studied so far. The sources which are responsible for these radiations in various countries are presence of 232Th content in sands and 238U along their descendants in groundwater, rocks, and soil of that areas. The level of these gamma rays was gauzed with the help of various techniques and devices such as scintillation survey meters, portable gamma SARAD meters, G.M. counters, portable and airborne gamma spectrometers and high-pressure ion chambers, respectively.