ABSTRACT

We live in an environment awash in radiation. Radiation emitted by radioactive nuclides, both inside and outside our bodies, interacts with our tissues. Electromagnetic radiation of all wavelengths, including radio waves, microwaves, radar, and light, of both manmade and natural origins, constantly, bombard us. Photons are far more abundant than matter in our universe; for every nucleon there are about 109 photons. Cosmic rays and the subatomic debris they create during interactions in the atmosphere also impinge on us. Neutrinos from fusion reactions in stars pervade the universe in such numbers that billions per second pass through every square centimeter of our skin. Most of this radiation such as neutrinos and radio waves, fortunately, passes harmlessly through us. Other radiation such as light and longer wavelength electromagnetic radiation usually interact harmlessly with our tissues. However, shorter wavelength electromagnetic radiation (ultraviolet light, X rays, and gamma rays) and charged particles produced by nuclear reactions can cause various degrees of damage to our cells.