Terrestrial Natural and Man-made Electromagnetic Noise

The terrestrial environment is continuously exposed to electromagnetic radiations which set up a “background” electromagnetic noise. For what concerns electromagnetic waves in the Non Ionizing Radiation band (NIR), i.e. for frequencies lower than 300 GHz, the background can have a natural or an artificial origin. In the first case electromagnetic radiations have generally an atmospheric or a cosmic origin while in the second case human technologies, implanted for power transmission and communications, are the non ‘natural’ cause. In this paper, a brief description of the natural and man-made electromagnetic noise in the NIR band has been reported. Natural noise shows a very large variety of sources that involve different physical phenomena and cover a wide range of frequency showing various propagation characteristics with an extremely broad range of power levels. Due to the technological expansion man-made electromagnetic noise is nowadays superimposed on the natural noise almost everywhere on Earth. In residential and business areas, man-made noise has increased dramatically in the last tens of years exceeding the natural one and in certain cases overwhelming the natural noise. This circumstance has brought some to consider possible negative influences on human life and living systems in general. In all cases however both contributions form the background in which the terrestrial environment is immersed and investigations and detailed measurements are still required to understand their relative power levels in the different frequency bands and their influence on life in general. Some aspects of the electromagnetic field interaction with biological systems are also presented.