Where does radiation come from?
In general, there are two kinds of radiation according to its origin: natural radiation and artificial radiation.
Natural radiation comes from cosmic rays from outer space and naturally occurring radioactive materials that exist in food, air and our natural habitat. Please click here for details.
Exposure in medical practice, mostly due to diagnostic x-rays, probably contributes the largest fraction of human's exposure to artificial radiation. Fallout of radioactive substances resulting from atmospheric nuclear weapon testing, luminous watches, ionization chambers, smoke detectors, etc. make up the balance. Please click here for details.
Percentage of different types of radiation dose in daily life