DIP... PAINT... LICK the brush. The rhythmic sequence was second nature to those known as luminators during the 1920s. Their task was simple—to apply radium paint to the tiny numerals encircling watch dials. Their occupational hazards were manifold—osteomyelitis, aplastic anemia, osteosarcoma, and mastoid carcinoma.
Dial painting required a deft hand and a finely pointed brush. While the first attribute may have been hereditary, the second was easily acquired. All it took to keep a brush pointed was a quick touch to the lips or tongue.
"Lip tipping" passed particles of the sticky paint to the teeth and tongue; it also transferred from 3 to 43 μg of radioactive substances each day. Thus, in a few years' time luminators could easily have swallowed 5 mg or more, at least 1 mg of which would be deposited in their bones, spleen, and liver, where it would remain, emitting a steady stream of