Radon and its isotopes, parent radionuclides, and decay products all contribute to an average inhaled dose of 1.26 m Sv/a.
Radon is unevenly distributed and variable with weather, such that much higher doses occur in certain areas of the world.
Most of these sources have been decreasing, due to radioactive decay since the formation of the earth, because there is no significant source of replacement.
Because of this, the present activity on Earth from uranium-238 is only half as much as it originally was because of its 4.5-billion-year half-life.
A radiation detector is a device used to detect, track, or identify high- energy particles, such as those produced by nuclear decay, cosmic radiation, and reactions in a particle accelerator.
Modern detectors are also used as calorimeters to measure the energy of detected radiation.
They may be also used to measure other attributes, such as momentum, spin, and charge of the particles.
This radiation interacts with atoms in the atmosphere to create an air shower of secondary radiation, including x-rays, muons, protons, alpha particles, pions, electrons, and neutrons.An airline crew typically gets an extra dose on the order of 2.2 m Sv (220 mrem) per year.Terrestrial radiation only includes sources that remain external to the body.Many shorter-half-life and therefore more intensely radioactive isotopes have not decayed out of the terrestrial environment because they are still being produced.Examples of these are radium-226 (a decay product of uranium-238) and radon-222 (a decay product of radium-226).