Where does radiation come from?
In general, there are two kinds of radiation according to its origin: natural radiation and artificial radiation.
Natural radiation
Natural radiation comes from cosmic rays from outer space and naturally occurring radioactive materials that exist in food, air and our natural habitat.
Artificial radiation
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.
Percentage of different types of radiation dose in daily life
| Natural | Man-made | ||
|---|---|---|---|
| Natural percentage | 85.5% | Man-made percentage | 14.5% |
| Radon | 42.5% | Medical | 14% |
| Gamma ray | 18% | Fallout | 0.2% |
| Cosmic ray | 14% | Miscellaneous | 0.2% |
| Internal | 11% | Nuclear discharge | < 0.1% |