A particle consisting of two protons and two neutrons emitted from the nucleus.
Low penetration: the mean range of a 5-MeV alpha particle in air is about 3.5 cm; in tissue its range is about 44 µ m (Shapiro).
For environmental dosimetry, particularly important as an internal emitter, especially in the respiratory passages, on bone surfaces, and in red marrow. Its energy is concentrated along short paths and can deliver high localized doses to sensitive surface regions.
An electron emitted from the nucleus.
The average range of a 1-MeV beta particle is about 3 m in air but only about 3 mm in tissue.
For environmental dosimetry, of primary concern as an internal emitter. Because of their relatively short range in tissue, beta particles principally irradiate the organs in which they originate.
Electromagnetic radiation, emitted as energy packets called photons, similar to light and radio waves but from a different energy region of the electromagnetic spectrum. X rays originate in the orbital electron field surrounding the nucleus; gamma rays are emitted from the nucleus.
Gamma radiation: to absorb 95% of the gamma energy from a 60Co source, 6 cm of lead, 10 cm of iron, or 33 cm of concrete would be needed.
For environmental dosimetry, important both for internal and external exposure. Gamma emitters deposited in one organ of the body can significantly irradiate other organs.