Radium

Radium is a chemical element with only radioactive isotopes.

The naturally occurring isotopes are formed during the radioactive decay of uranium (U-235, U-238) and thorium (Th-232), which are present in all soils and rocks. Naturally occurring radium isotopes that can contribute to a significant radiation dose to humans are

• Radium-224 (physical half-life 3.66 days; alpha emitter),
• Radium-226 (physical half-life 1600 years; alpha emitter) and
• Radium-228 (physical half-life 5.75 years; beta emitter).

Alpha emitters are again among the daughter nuclides of these radium isotopes.

Radium is chemically similar to the mineral calcium. Most of the radium that enters the human body with food is excreted immediately. Only a small proportion is absorbed into the body via the gastrointestinal tract, where about a quarter to a third is initially stored in bones and then slowly released from bones. In the case of short-lived radium isotopes, the activity in the human body decreases rapidly due to radioactive decay corresponding to the physical half-life.

Radium-223 (physical half-life 11.4 days; alpha emitter) is produced artificially for medical purposes. This radium isotope is used to treat bone metastases.