The History of Radium

Elaine Lui
March 23, 2021

Submitted as coursework for PH241, Stanford University, Winter 2021


Fig. 1: Pierre and Marie Sklodowska Curie. (Source: Wikimedia Commons).

Radium (Ra) is a highly radioactive alkaline earth metal that is naturally found in uranium ores. Its appearance is silvery white in its pure form, although it reacts readily with nitrogen in the air to form radium nitride, leaving behind a blackened surface layer. [1] Radium has 33 known isotopes, all of which are radioactive, and the most common and long-lived isotope is Ra-226, which comprises one part per trillion of Earth's crust. [2] From the initial discovery of radium in 1898 by the Curies to its widespread use in the Golden Age, and finally to its rapid decline, the radium industry has a remarkable history worth examining more closely.

The Curies Discover Radium

Marie Sklodowska was studying physics and mathematics at Sorbonne University in 1894 when she met Pierre Curie, who would later become her husband (Fig. 1). Pierre was a professor at the Paris School of Physics and Chemistry, and their mutual passion for the natural sciences drew them together. [3] Pierre took on Marie as his doctoral student, and the two were intrigued by the work of fellow physicist Henri Becquerel, who had discovered in 1896 an "invisible radiation" emitted by uranium that caused photographic plates to darken after contact with uranium crystals. Becquerel's work became the inspiration for Marie's doctoral work. [3] The breakthrough moment for the Curies occurred two years later, when Marie was researching pitchblende uranium ore from the Joachimsthal mine in Poland and noticed 2.5 times more radiation emitted from the ore than could be explained by the uranium content. [4] She hypothesized that the pitchblende contained another element - one more radioactive than uranium. After a lengthy isolation process, Marie obtained a radium chloride precipitate and coined the term radioactivity to describe the radiation emitted from atomic decay. [5] The groundbreaking subsequent work in radium isolation and purification ultimately granted Marie, Pierre, and Henri Becquerel the Nobel Prize in 1903.

Golden Age of Radium

Fig. 2: Waveguide in a radiation therapy system. The smooth copper interior speeds up launched electrons to form a radiation beam, which can target a cancerous tumor. (Source: Wikimedia Commons).

As radium grew in press and popularity, so did the industrialization and commercialization of radium, which was branded as a refreshing and vitalizing element for boosting health. Radium clinics and spas were established, and companies began selling radioactive dressings and pills and radium-infused chocolates and water to the public. [6] In the medical community, doctors began to use early stages of radiotherapy for cancer patients, wherein a radiation beam could be focused on a tumor, such as shown in Fig. 2. When WWI swept over Europe and there was a demand for medical treatment on the battlefront, Marie Curie herself devised and built radiology cars from donated vans, trucks, and limousines, which were reconfigured to carry diagnostic radiology equipment, such as X-ray units and fluoroscopes, to the front lines. [7]

The Tragedy and Legacy of the Radium Girls

One of the most infamous and tragic commercial uses of radium was in the luminescent paints that decorated the dials of clocks and watches starting in 1917 and through the 1930s. Undark, one of these commercial paints, was a mixture of Ra-226 and zinc sulfide, the latter of which would luminesce when struck by the alpha particles emitted from radium. [8] Many of the factory workers for The Radium Dial Company, which produced luminescent watches, were young women (as shown in Fig. 3), whose work painting the dials was a streamlined process coined "lip, dip, and paint." [9] The workers would use their mouths to shape the brushes of the paintbrushes to a tapered point for an average of 250 times a day, which amounted to ingesting almost 2 grams of paint and up to 43 micrograms of radioactive materials per day. [8,9] Slowly but surely, all of these dial workers - later called the Radium Girls - began to experience radioactive poisoning. Symptoms of illness included jaw necrosis and tooth loss, nonhealing ulcers, bone fractures, anemia, and cancer, ultimately leading to violent and agonizing death. [9] In the late 1920s, as the adverse health effects of radium exposure became apparent, many of the women working at the plant filed a lawsuit against the company, and industrial use of radium began to decline. The legacy of the Radium Girls include the formation of labor safety laws and standards, workers' compensation lows, and the modern-day Occupational Safety and Health Administration (OSHA). [9]

Medical Uses of Radium Today

Fig. 3: A woman painting a watch dial with radioactive luminescent paint. (Source: Wikimedia Commons).

By the 1950s, Ra-226, the most stable isotope of radium, had been replaced in radiation therapy departments by artificial radioisotopes, such as Cs-137 and Ir-192, and by the 1960s, the commercial use of radium had all but ceased. [3] Today, radium is scarcely used for medical treatments because of its high radioactivity. One exception is in prostate and breast cancer treatments for medically inoperable patients with high risk factors and comorbidities. For these patients, the radioisotope Ra-223 is used to treat the sarcomas, which often spread deep within the bone tissue. [10] However, due to the high costs of radioisotope treatments, the modern knowledge of the dangers of high exposure levels to radioactivity, and the lack of accessibility of radium, the trend of radium's declining use in our society will likely continue in the upcoming decades.

© Elaine Lui. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] J. C. Villforth, "Problems in Radium Control," Public Health Rep. 79, 337 (1964).

[2] G. Audi, et al., "The NUBASE 2016 Evaluation of Nuclear Properties," Chinese Phys. C 41, 03001 (2017).

[3] J. J. Mazeron and A. Gerbaulet, "The Centenary of Discovery of Radium," Radiother. Oncol. 49, 205 (1998).

[4] F. P. Carvalho, "Marie Curie and the Discovery of Radium," in The New Uranium Mining Boom, ed. by B. Merkel and M. Schipek (Springer, 2012).

[5] J. P. Adloff, "The Laboratory Notebooks of Pierre and Marie Curie and the Discovery of Polonium and Radium", Czech. J. Phys. 49, Suppl. 1, 15 (1999).

[6] C. E. Murdock, "Selling Scientific Authority: Radium Spas, Advertising and Popular Understandings of Radioactivity in Germany, 1900-1937," Ger. Hist. 35, 21 (2017).

[7] S. Rockwell. "The Life and Legacy of Marie Curie," Yale J. Biol. Med. 76, 167 (2003).

[8] M. Estrada, "Radium Dials and the Radium Girls," Physics 241, Stanford University, Winter 2014.

[9] R. B. Gunderman and A. S. Gonda, "Radium Girls," Radiology 274, 314 (2015).

[10] M. K. Thompson, et al., "Practice-Changing Radiation Therapy Trials for the Treatment of Cancer: Where Are We 150 Years After the Birth of Marie Curie?", Brit. J. Cancer 119, 389 (2018).