Sources of Radiation Page Content Radiation is part of our natural environment. We are exposed to radiation from materials in the earth itself, from naturally occurring radon in the air, from outer space and from inside our own bodies (as a result of the food and water we consume). What is nuclear radiation? After more than 80 years of intensive scientific study, radiation is the most understood, easily detected, precisely measured and strictly regulated of all environmental agents. Radiation contributed by human technology is identical to naturally occurring radiation. Most of this radiation comes from X-rays and radioactive materials used in medicine. Mining, burning fuels and buildings also contribute to radiation doses. So does fallout from past testing of nuclear weapons, color television and smoke detectors. Radiation is measured in units called millirems. The average dose per person from all sources is about 620 millirems per year. It is not, however, uncommon for any of us to receive far more than that in a given year, often due to medical procedures we may undergo. International standards allow exposure to as much as 5,000 millirems per year for those who work with and around radioactive material. Types of radiation Usually the word “radiation” is used to mean ionizing radiation – radiation that has so much energy it changes the electric charge of the atoms it strikes. Ionizing radiation can take the form of either particles or waves. The waves include X-rays and gamma rays. Particle radiation is made up of alpha and beta particles and neutrons.