Radium was formerly used in self-luminous paints for watches, nuclear panels, aircraft switches, clocks, and instrument dials.
A typical self-luminous watch that uses radium paint contains around 1 microgram of radium.
In the mid-1920s, a lawsuit was filed against the United States Radium Corporation by five dying "Radium Girls" – dial painters who had painted radium-based luminous paint on the dials of watches and clocks.
The dial painters were instructed to lick their brushes to give them a fine point, thereby ingesting radium.
Their exposure to radium caused serious health effects which included sores, anemia, and bone cancer.
This is because the body treats radium as calcium and deposits it in the bones, where radioactivity degrades marrow and can mutate bone cells.

During the litigation, it was determined that the company's scientists and management had taken considerable precautions to protect themselves from the effects of radiation, yet had not seen fit to protect their employees.
Additionally, 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.

As a result of the lawsuit, the adverse effects of radioactivity became widely known, and radium-dial painters were instructed in proper safety precautions and provided with protective gear.
In particular, dial painters no longer licked paint brushes to shape them (which caused some ingestion of radium salts).
Radium was still used in dials as late as the 1960s, but there were no further injuries to dial painters.
This highlighted that the harm to the Radium Girls could easily have been avoided.

From the 1960s the use of radium paint was discontinued.
In many cases luminous dials were implemented with non-radioactive fluorescent materials excited by light; such devices glow in the dark after exposure to light, but the glow fades.
Where long-lasting self-luminosity in darkness was required, safer radioactive promethium-147 (half-life 2.6 years) or tritium (half-life 12 years) paint was used; both continue to be used today.
These had the added advantage of not degrading the phosphor over time, unlike radium.
Tritium emits very low-energy beta radiation (even lower-energy than the beta radiation emitted by promethium) which cannot penetrate the skin, rather than the penetrating gamma radiation of radium and is regarded as safer.

Clocks, watches, and instruments dating from the first half of the 20th century, often in military applications, may have been painted with radioactive luminous paint.
They are usually no longer luminous; however, this is not due to radioactive decay of the radium (which has a half-life of 1600 years) but to the fluorescence of the zinc sulfide fluorescent medium being worn out by the radiation from the radium.
The appearance of an often thick layer of green or yellowish brown paint in devices from this period suggests a radioactive hazard.
The radiation dose from an intact device is relatively low and usually not an acute risk; but the paint is dangerous if released and inhaled or ingested.
Radium was formerly used in self-luminous paints for watches, nuclear panels, aircraft switches, clocks, and instrument dials. A typical self-luminous watch that uses radium paint contains around 1 microgram of radium. In the mid-1920s, a lawsuit was filed against the United States Radium Corporation by five dying "Radium Girls" – dial painters who had painted radium-based luminous paint on the dials of watches and clocks. The dial painters were instructed to lick their brushes to give them a fine point, thereby ingesting radium. Their exposure to radium caused serious health effects which included sores, anemia, and bone cancer. This is because the body treats radium as calcium and deposits it in the bones, where radioactivity degrades marrow and can mutate bone cells.
During the litigation, it was determined that the company's scientists and management had taken considerable precautions to protect themselves from the effects of radiation, yet had not seen fit to protect their employees. Additionally, 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.
As a result of the lawsuit, the adverse effects of radioactivity became widely known, and radium-dial painters were instructed in proper safety precautions and provided with protective gear. In particular, dial painters no longer licked paint brushes to shape them (which caused some ingestion of radium salts). Radium was still used in dials as late as the 1960s, but there were no further injuries to dial painters. This highlighted that the harm to the Radium Girls could easily have been avoided.
From the 1960s the use of radium paint was discontinued. In many cases luminous dials were implemented with non-radioactive fluorescent materials excited by light; such devices glow in the dark after exposure to light, but the glow fades. Where long-lasting self-luminosity in darkness was required, safer radioactive promethium-147 (half-life 2.6 years) or tritium (half-life 12 years) paint was used; both continue to be used today. These had the added advantage of not degrading the phosphor over time, unlike radium. Tritium emits very low-energy beta radiation (even lower-energy than the beta radiation emitted by promethium) which cannot penetrate the skin, rather than the penetrating gamma radiation of radium and is regarded as safer.
Clocks, watches, and instruments dating from the first half of the 20th century, often in military applications, may have been painted with radioactive luminous paint. They are usually no longer luminous; however, this is not due to radioactive decay of the radium (which has a half-life of 1600 years) but to the fluorescence of the zinc sulfide fluorescent medium being worn out by the radiation from the radium. The appearance of an often thick layer of green or yellowish brown paint in devices from this period suggests a radioactive hazard. The radiation dose from an intact device is relatively low and usually not an acute risk; but the paint is dangerous if released and inhaled or ingested.
Radium