Another industry also began using radium, but not for its "curative" abilities. On its own, the element radium glows dimly in the dark. When mixed with a substance like zinc, it takes on a bright, green color that makes a glowing paint.
Industrial manufacturers realized the paint — known as radium paint — could be used to make instruments and clocks visible at night. Demand grew as World War I began; in 1914, the United States Radium Corporation, or USRC, was founded.
USRC hired young women to paint these instruments with radium paint. Their small hands were suited to the detailed work, and the jobs paid well.
"At the height of the industry in the early 1920s, about 2,000 women were employed," says Stemm. "Estimates of the total number of women employed in the industry between 1917 and 1935 vary, but a number approaching 10,000 is not unreasonable."
The women would mix their own paint from radium dust and other ingredients. They were soon known as "ghost girls," because the radium dust made their skin, hair and clothes glow. Some of the women even used radium paint on their teeth to brighten their smiles.
"Once the paint was mixed, the extremely fine detail painting required very sharply pointed paint brushes," says Stemm. "To ensure a sufficiently sharp point, the women were told to use their lips and tongue to shape the brush." They had to do this repeatedly throughout the day to keep that fine point, which meant the women ingested radioactive paint constantly.
The women's employers at Radium Corporation assured them the paint was harmless, but many of the women soon fell ill, some severely with necrosis of the jaw.
"This extremely painful and disfiguring condition was the most common of the diseases suffered by the [radium girls]," Stemm says. "Radium poisoning caused the victims' jaws to disintegrate over time, eventually killing them."
By the time the first dial painter died in 1923, the medical community had begun to suspect that radium exposure was the cause.