Carbon dating decay curve
The major radionuclides of concern are potassium, uranium, and thorium and their decay products.Some of these decay products, like radium and radon, are intensely radioactive but occur in low concentrations.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.The immediate dose from cosmic radiation is largely from muons, neutrons, and electrons, and this dose varies in different parts of the world based on the geomagnetic field and altitude.This radiation is much more intense in the upper troposphere (around 10 km in altitude) and is therefore of particular concern for airline crews and frequent passengers, who spend many hours per year in this environment.Radon and its isotopes, parent radionuclides, and decay products all contribute to an average inhaled dose of 1.26 m Sv/a.
Examples of these are radium-226 (a decay product of uranium-238) and radon-222 (a decay product of radium-226).
Gaseous ionization detectors use the ionizing effect of radiation upon gas-filled sensors.
If a particle has enough energy to ionize a gas atom or molecule, the resulting electrons and ions cause a current flow, which can be measured.
This is four times more than the worldwide average artificial radiation exposure, which in the year 2008 amounted to about 0.6 m Sv per year.
In some wealthier countries, such as the US and Japan, artificial exposure is, on average, greater than the natural exposure, due to greater access to medical imaging.