Watch dial, radium paint

Around the beginning of this century, cancer and illness was associated with excessive use of X-rays. Watch dial painters got mouth cancer from radium in the paint. It soon was realized that radiation has health effects. The measures of energy deposition concepts introduced... 

At one time, women painted clock and watch dials with luminous radium paint that was a mixture of radium salts and zinc sulfide. They would place the small brushes between their lips and tongue to make the bristles more pointed, in order to paint fine lines with the radium paint. Over the years, they developed cancers that resulted in badly eaten-away and disfigured lips and jaws. Once the danger was known, luminous radium paint was banned for this use. Today, promethium (Pm-147), with a half-life of 2.4 years, is used for this purpose. 

The name comes from the Latin radius, meaning ray. It was discovered by Marie and Pierre Curie in 1898 when they were studying uranium and other radioactive materials found in pitchblende. There is about 1 g of radium in 7 tons of pitchblende, but it is 3xl05 times more radioactive than uranium. It was isolated as a metallic element in 1911 by Marie Curie and Andre-Louis Debieme (1874-1949). Radium exists in small quantities associated with uranium ores. Radium is phosphorescent, so it has been used to make luminous paint, especially for watch dials, but, because it is highly radioactive, most uses are related to nuclear medicine or the energy industry. Radon gas is produced from radium and is a harmful by-product. 

After the war-time demand had ceased, other applications of the paint were made and quickly became popular. Now, in addition to watch and clock dials, luminous paint is used to mark street signs, door plates, push buttons, or almost anything that may need to be located in the dark. The amount of radium used in this manner has been enough to cause serious concern in regard to the future supply, but the largest use of radium at present is in treating cancer. 

It is well known that the risk of acquiring many diseases is directly related to occupation. Some examples of disease hazards related to occupation include the development of bone cancers among workers who applied radium paint to watch dials and hands, the occurrence of lead poisoning in battery workers, bladder cancers in aniline dye workers and lung cancers in miners of radioactive ores. 

The heaviest member of the alkaline earth metals is radium (Ra), a naturally radioactive element discovered by Pierre and Marie Cnrie in 1898. Radinm was initially isolated from the nraninm ore pitchblende, in which it is present as approximately 1.0 g per 7.0 metric tons of pitchblende. How many atoms of radinm can be isolated from 1.75 X 10 g pitchblende (1 metric ton = 1000 kg) One of the early uses of radium was as an additive to paint so that watch dials coated with this paint wonld glow in the dark. The longest-lived isotope of radinm has a half-life of 1.60 X 10 years. If an antique watch, manufactured in 1925, contains 15.0 mg radinm, how many atoms of radinm will remain in 2025 ... 

In the past, radium was added to some paints that were used on watch dials. The radium made the dial glow. 

Until the 1960s, radium was a component of the luminous paints used for watch and clock dials, instrument panels in airplanes, military instruments, and compasses (Blaufox 1988). 

A second radionuclide to which humans are likely to be exposed is radium, Ra. Occupational exposure to radium is known to have caused cancers in humans, most tragically in the cases of a number of young women who were exposed to radium because of their employment in painting luminescent radium-containing paint on the dials of watches, clocks, and instruments.9 These workers would touch their tongues with the very fine brushes used for the radioactive paint in order to point the brushes. Many eventually developed bone cancer and died from this malady. 

An awful fate befell many of the young women hired to paint radium onto the dials of watches, so that they would glow in the dark. The original luminous watches had been designed for soldiers fighting in the trenches during the First World War, but their novelty stimulated a... 

USE Pigment For paints, oilcloths, linoleum, leather, dental ruhber, etc., especially in the form of lithopone mixed with ZnO as "mineral white. Anhydr zinc sulfide is used in x-ray screens and with a trace of a radium or mesothorium salt In luminous dials of watches, etc. also television screens. 

Few commercial uses exist for the radioactive decay products of uranium. The highly radiotoxic Ra was used in luminous paint on watch and instrument dials and, during the 1920s and 1930s, was also widely used in radiotherapy to treat tumors as well as therapy for diabetes, sciatica, uremia, rheumatism, and even impotence (Genet 1998). The radium decay product, Rn, with its half-life of 3.8 days is still used, after sealing it in minute tubes called seeds or needles, for local irradiations in patients. 

In the past, uranium was also used to color glass (from as early as 79 AD), and deposits were once mined to obtain its decay product, radium. This element was used in luminous paint, particularly on the dials of watches and aircraft instruments, and in medicine for the treatment of diseases. 

The isotope Pm is commercially available and has found some use. Its emission of low-energy 3-particles is used industrially to measure the thickness of strip steel and paper. To some extent it is also used in miniature batteries with a useful hfe of about five years. These have been tested for such diverse purposes as pacemakers and guided missiles. A paint containing Pm and a material that fluoresces with a bluish-green color after being hit by the P-particles may be used for hour hands and dials in watches. Promethium has replaced radium for reasons of health. 

Radium was also utilized in self-luminous paints for watch, clock and instrument dials and for emission in automatic control systems. Safer radioisotopes for technical properties, such as cobalt-60 and cesium-137, can nowadays be tailored in nuclear reactors and have entirely replaced radium. This has released us from the need for radium, which is a great advantage, as radium is so difficult to handle from an environmental point of view. It forms gaseous radon, affecting its surroundings. And the problem remains for a long time, as the most usual radidum isotope, Ra, has a half-life of 1600 years. Nowadays the use of radium has ceased. The annual amount manufactured is only round 100 g. 

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