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Radium is a radioactive chemical element which has the symbol Ra and atomic number 88. Its appearance is almost pure white, but it readily oxidizes on exposure to air, turning black. Radium is an alkaline earth metal that is found in trace amounts in uranium ores. Its most stable isotope, 226. Ra, has a half-life of 1601 years and decays into radon gas.

Radium was discovered by Marie Curie and her husband Pierre on December 21, 1898 in pitchblende coming from North Bohemia, in the Czech Republic (area around Jáchymov). While studying pitchblende the Curies removed uranium from it and found that the remaining material was still radioactive. They then separated out a radioactive mixture consisting mostly of barium which gave a brilliant green flame color and crimson carmine spectral lines which had never been documented before. The Curies announced their discovery to the French Academy of Sciences on December 26, 1898.

Radium-226, the most common isotope, is an alpha emitter, with accompanying gamma radiation, and has a half-life of about 1600 years. Radium-228, is principally a beta emitter and has a half-life of 5.76 years. Radium-224, an alpha emitter, has a half life of 3.66 days. Radium decays to form isotopes of the radioactive gas radon, which is not chemically reactive. Stable lead is the final product of this lengthy radioactive decay series.

Radium was formerly used in self-luminous paints for watches, nuclear panels, aircraft switches, clocks, and instrument dials. In the mid-1920s, a lawsuit was filed by five dying "Radium Girls" dial painters who had painted radium-based luminous paints on the dials of watches and clocks. The dial painters' exposure to radium caused serious health effects which included sores, anemia and bone cancer. This is because radium is treated as calcium by the body, and deposited in the bones, where radioactivity degrades marrow and can mutate bone cells.
During the litigation, it was determined that company scientists and management had taken considerable precautions to protect themselves from the effects of radiation, yet had not seen fit to protect their employees. Worse, for several years, the companies had attempted to cover up the effects and avoid liability by insisting that the Radium Girls were instead suffering from syphilis. This complete disregard for employee welfare had a significant impact on the formulation of occupational disease labor law.


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