Natural Radiation and Environment

Radioactivity and radionuclides have been omnipresent since the formation of the universe and are inescapable. Natural radiation encompasses various sources of ionizing radiation originating from both terrestrial and extra-terrestrial sources. Terrestrial sources of radiation include primordial radionuclides present in the Earth’s crust, such as uranium, thorium, and their decay products such as radium, radon, lead, and polonium contributing to the background radiation levels. Additionally, cosmic radiation, coming from the Sun and other celestial bodies, interacts with Earth’s atmosphere, forming secondary particles that contribute to the overall radiation exposure. Anthropogenic activities also give rise to man-made radionuclides and technologically enhanced naturally occurring radioactive materials. All these sources make up the natural background radiation environment we humans have been living in, for ages. This has resulted in continuous exposure to the natural radiation sources prevailing all around us in the atmosphere, hydrosphere, geosphere, and biosphere, since time immemorial. The background radiation levels and dose rates are elevated in certain regions of the world with enhanced levels of natural radioactivity. Due to the chemically dissimilar nature of the radionuclides, their behaviour, mobility, and chemical forms in diverse environments are also different. Understanding the natural radiation environment is crucial for assessing its potential health effects on living organisms and for establishing baseline measurements in various geographical locations. This necessitates the creation of national and global maps of background dose rates in geographically and geologically different regions of the world. This chapter dives into the multifaceted aspects of natural radiation in the environment, exploring its diverse origins, distribution in environmental compartments, radionuclide behaviour, influencing factors, and background dose rate, crucial for public dose assessment.