Radium dials
Encyclopedia
Radium dials are watch
, clock
and other instrument dial
s painted with radioluminescent paint
containing radium
. The 1900s were the peak of radium dial production, as radiation poisoning
was then unknown; subsequently, radium dials have largely been replaced by tritium based light sources.
. The disease, radium-induced osteonecrosis
, was recognized as an occupational disease
in 1925 after a group of radium painters, known as the Radium Girls
, from the United States Radium Corporation
sued. By 1930 all dial painters stopped pointing their brushes by mouth. Stopping this practice drastically reduced the amount of radium ingested and therefore, the incidence of malignancy, to zero by 1950 among the workers who were studied.
"Luminous Processes employees interviewed by a journalist in 1978 had been left ignorant of radium's dangers. They were told that eliminating lippointing had ended earlier problems. They worked in unvented rooms, they wore smocks that they laundered at home. Geiger counters could pick up readings from pants returned from a dry cleaner and from clothes stored away in a cedar chest."
, not the decay of the radium, which has a half-life
of about 1600 years. Thus, even very old radium dials remain radioactive. Radium paint can be ingested by inhaling flaking paint from radium dials, and lead to poisoning.
One estimate of radiation exposure caused by wearing a watch painted with radium is 10-1000 millirads.
Watch
A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...
, clock
Clock
A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece...
and other instrument dial
Dial (measurement)
A dial is generally a flat surface, circular or rectangular, with numbers or similar markings on it, used for displaying the setting or output of a timepiece, radio, clock, watch, or measuring instrument...
s painted with radioluminescent paint
Luminous paint
Luminous paint or luminescent paint is paint that exhibits luminescence. In other words, it gives off visible light through fluorescence, phosphorescence, or radioluminescence.-Fluorescent paint:...
containing radium
Radium
Radium is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226,...
. The 1900s were the peak of radium dial production, as radiation poisoning
Radiation poisoning
Acute radiation syndrome also known as radiation poisoning, radiation sickness or radiation toxicity, is a constellation of health effects which occur within several months of exposure to high amounts of ionizing radiation...
was then unknown; subsequently, radium dials have largely been replaced by tritium based light sources.
Brands
- UndarkUndarkUndark was a trade name for luminous paint made with a mixture of radioactive radium and zinc sulfide, as produced by the U.S. Radium Corporation between 1917 and 1938. It was used primarily in watch dials...
produced by the United States Radium CorporationUnited States Radium CorporationThe United States Radium Corporation was a company, most notorious for its operations between the years 1917 to 1926 in Orange, New Jersey, in the United States that led to stronger worker protection laws... - Luna produced by the Radium Dial CompanyRadium Dial CompanyThe now defunct Radium Dial Company, was one of a few United States companies along with the United States Radium Corporation, involved in the painting of clocks, watches and other instrument dials using radioluminescent paint containing radium. These dials are collectively known as radium dials...
- Marvelite produced by the Cold Light Manufacturing Company (a subsidiary of the Radium Company of Colorado)
History
Radium dials were almost always painted by young women, who used to 'point' their brushes by licking and shaping the bristles prior to painting the fine lines and numbers on the dials. This practice resulted in the ingestion of radium, which caused serious jaw-bone degeneration and malignancy and other dental diseases reminiscent of phossy jawPhossy jaw
Phossy jaw, formally phosphorus necrosis of the jaw, is an occupational disease of those who work with white phosphorus, also known as yellow phosphorus, without proper safeguards. It was most commonly seen in workers in the match industry in the 19th and early 20th century...
. The disease, radium-induced osteonecrosis
Radium jaw
Radium jaw is an occupational disease brought on by the ingestion and subsequent absorption of radium into the bones of radium dial painters. The symptoms are necrosis of the mandible and the maxilla as well as constant bleeding of the gums and after some time, severe distortion due to bone...
, was recognized as an occupational disease
Occupational disease
An occupational disease is any chronic ailment that occurs as a result of work or occupational activity. It is an aspect of occupational safety and health. An occupational disease is typically identified when it is shown that it is more prevalent in a given body of workers than in the general...
in 1925 after a group of radium painters, known as the Radium Girls
Radium Girls
The Radium Girls were female factory workers who contracted radiation poisoning from painting watch dials with glow-in-the-dark paint at the United States Radium factory in Orange, New Jersey around 1917....
, from the United States Radium Corporation
United States Radium Corporation
The United States Radium Corporation was a company, most notorious for its operations between the years 1917 to 1926 in Orange, New Jersey, in the United States that led to stronger worker protection laws...
sued. By 1930 all dial painters stopped pointing their brushes by mouth. Stopping this practice drastically reduced the amount of radium ingested and therefore, the incidence of malignancy, to zero by 1950 among the workers who were studied.
"Luminous Processes employees interviewed by a journalist in 1978 had been left ignorant of radium's dangers. They were told that eliminating lippointing had ended earlier problems. They worked in unvented rooms, they wore smocks that they laundered at home. Geiger counters could pick up readings from pants returned from a dry cleaner and from clothes stored away in a cedar chest."
Safety
Although radium dials may no longer produce light, this is frequently due to the breakdown of the crystal structure of zinc sulfideZinc sulfide
Zinc sulfide is a inorganic compound with the formula ZnS. ZnS is the main form of zinc in nature, where it mainly occurs as the mineral sphalerite...
, not the decay of the radium, which has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of about 1600 years. Thus, even very old radium dials remain radioactive. Radium paint can be ingested by inhaling flaking paint from radium dials, and lead to poisoning.
One estimate of radiation exposure caused by wearing a watch painted with radium is 10-1000 millirads.
See also
- Radium jawRadium jawRadium jaw is an occupational disease brought on by the ingestion and subsequent absorption of radium into the bones of radium dial painters. The symptoms are necrosis of the mandible and the maxilla as well as constant bleeding of the gums and after some time, severe distortion due to bone...
- Radium Dial CompanyRadium Dial CompanyThe now defunct Radium Dial Company, was one of a few United States companies along with the United States Radium Corporation, involved in the painting of clocks, watches and other instrument dials using radioluminescent paint containing radium. These dials are collectively known as radium dials...
- United States Radium CorporationUnited States Radium CorporationThe United States Radium Corporation was a company, most notorious for its operations between the years 1917 to 1926 in Orange, New Jersey, in the United States that led to stronger worker protection laws...
- RadioluminescenceRadioluminescenceRadioluminescence is the phenomenon by which luminescence is produced in a material by the bombardment of ionizing radiation such as beta particles.-Tritium:...
- Radioactive phosphors