Radium girls
They had worked at a factory on Orange, New Jersey. Their job was to paint the dials of watches with radium paint, so that the numbers would glow in the dark. The substance used to paint was luminous paint, which contained radium. Radium is radioactive, and causes radiation sickness. The workers used paintbrushes to draw fine lines; the brush would only draw such a line when it was wet.  The girls would put the brushes in their mouths to lick them. The women were told the paint was harmless. Over time, they ingested deadly amounts of radium paint.