The last of the Radium girls, Mae Keane, died in 2014, aged 107. The reports of her death did not focus on her extraordinary long life, but on how she survived so long. She should have died 9 decades earlier.
The Radium Girls
In 1898, while studying radio activity of Uranium, Marie Curie and Pierre Curie found that the nature of radiation emitted could not come from Uranium alone. They discovered traces of two new elements in Uranium ore – Polonium 84 and Radium 88.
Radium undergoes spontaneous α particle decay. Doctors found that when exposed to Radium cancerous tumours shrink. This led to proliferation of many products associated with Radium by commercial interests seeking to make a quick profit. Radium Soda, Radium Tooth Paste, Cakes, Lipstick and even Radium Water flooded the market. Salesmen promised that Radium could extend people’s lives, pump up their sex drive and make women more beautiful.
It was also found that Radium decay releases particles that ionize nearby materials creating positively charged ions that pull electrons from nearby atoms. When electrons return to their natural (previous) state they release energy in the form of light. Thus, Radium glows in dark as long as it is radioactive.
William Hammer used glue and zinc sulphide to create a luminous paint which was used in toys to gun sights but mainly in watch dials to make them visible in dark.
Luminous paints were marketed by US Radium corporation under the brand name “Undark”
The Radium Girls
US Radium corporation employed several thousand girls to work in watch factories to paint radium on the numbers of watch face. Even the scientists who worked with Radium worked from behind lead shields. But women workers were not afforded any such protection, instead were encouraged to use their lips and thumb to shape the brush tips.
To get the numbers small enough, new hires were taught to do something called “lip pointing.” After painting each number, they were to put the tip of the paintbrush between their lips to sharpen it. Twelve numbers per watch, upwards of 200 watches per day — and with every digit, the girls swallowed a little bit of radium.
The women were instructed to point their brushes because using rags, or a water rinse, caused them to waste too much time and waste too much of the material made from powdered radium, gum arabic and water. Some also painted their fingernails, face and teeth with the glowing substance.
So what is the problem?
Radium has properties similar to Calcium. Bones, teeth and other tissues absorb Radium. The women contracted tumour, bone marrow damage, leukemia, teeth damage, damaged jaw bones, mouth cancers and anaemia. Many of them died young.
“There was one woman who went to the dentist went to pull a tooth and he pulled her entire jaw out when he did it. “Their legs broke underneath them. Their spines collapsed.”
In all, by 1927, more than 50 women had died as a direct result of radium paint poisoning.
To understand what happened we should understand radioactivity of Radium
The radioactivity of Radium depends on its half life, decay constant and the energy of α particles emitted. Shorter the half life faster it decays, more α particles are emitted in given time with more energy. These properties (or the activity) of Radium explains what happened to Radium girls.
Radiation from a radio active material can be measured using Geiger Counter. Take a lump of Radioactive material and measure its activity. Plot the clicks recorded in Geiger Counter (N) to Time (t). The curve is an exponential curve.
N = N0 e–λt fits the curve
The initial quantity N0 decreases to N after t seconds. λ – decay constant which varies from element to element. If decay constant of an element is large it will decay fast and more material will transform in short time and vice versa.
Half life time ( tH) of a radioactive element is the time taken for the intial quantity (N0) to become half (N0/2)
N0 /2 = N0 e–λtH
1/2 = e–λtH
ln 1/2 = -λtH
– ln 2 = -λtH
tH = ln2 /λ
The energy of the α particles emitted from Radium 224 is 5.68 eV and it has a half life of 3.6 days. This is a relatively short half life time compared to many other radioactive elements. Hence, the women workers exposed to Radium without any protective measures succumbed to its effect.
So how did Mae Keane escape early death?
Mae Keane was hired at a factory in Waterbury, Conn in 1924. Her first day, she remembers, she didn’t like the taste of the radium paint. It was gritty.
“I wouldn’t put the brush in my mouth,” she recalled many years later.
After just a few days at the factory, the boss asked her if she’d like to quit, since she clearly didn’t like the work. She gratefully agreed.
“I often wish I had met him after to thank him,” Keane said, “because I would have been like the rest of them.” Over the years, she had some health problems — bad teeth, migraines, two bouts with cancer.
There’s no way to know if her time in the factory contributed.
Radium Girls by Rose Todaro
Radioactivity: Half Life
Radioactivity: Decay Constant