A highly radiotoxic element. 1 g produces 3.7 × 10¹⁰ disintegrations per second. Inhalation, ingestion, or bodily exposure can lead to lung cancer, bone cancer, osteitis, skin damage, and blood dyscrasias. A common air contaminant. Radium replaces calcium in the bone structure and is a source of irradiation to the blood-forming organs. The ingestion of luminous dial paint prepared from radium caused death in many of the early dial painters before the hazard was fully understood. The data on these workers have been the source of many of the radiation precautions and the maximum permissible levels for internal emitters that are now accepted. ²²⁶Ra is the parent of radon and the precautions described under ²²²Rn should be followed. ²²⁸Ra is a member of the thorium series. It was a common constituent of luminous paints, and, while its low beta energy was not a hazard, its daughters in the series may have been a causative agent in the deaths of the radium dial painters following World War I. It is metabolized in the same way as any other radium isotope and it is a source of thorium. The precautions recommended under ²²⁰Rn should be followed. Highly dangerous; must be kept heavily shielded and stored away from possible dissemination by explosion, flood, etc.

Radiation Hazard: Natural isotope ²²³Ra (Actinium-X, Actinium Series), T_1/2 = 11.4 days, decays to radioactive ²¹⁹Rn by alphas of 5.5–5.7 MeV. Natural isotope ²²⁴Ra (Thorium-X, Thorium Series), T_1/2 = 3.6 days, decays to radioactive ²²⁰Rn by alphas of 5.7 MeV. Natural isotope ²²⁶Ra (Uranium Series), T_1/2 = 1600 years, decays to radioactive ²²²Rn by alphas of 4.8 MeV. Natural isotope ²²⁸Ra (Mesothorium = 1, Thorium Series), T_1/2 = 6.7 years, decays to radioactive ²²⁸Ac by betas of 0.05 MeV.