Women painting alarm clock faces, Ingersoll factory, January 1932.

UNITED KINGDOM - FEBRUARY 23: Women painting alarm clock faces, Ingersoll factory, January 1932. Photograph by Cardew of women using luminous paint at the Ingersoll Watch and Clock Factory. Using Radium 226 for clock and watch dial luminosity became popular in the 1920s - before the profound risk to health was fully understood. Workers would often lick the paintbrush to achieve a finer point - directly ingesting the radium. Radium poisoning caused bone cancer and even fatalities amongst the largely young, female workforce. Radium's use in clocks and watches was banned by the UK Radioactive Substances Act of 1960, enforced in 1963. From the Daily Herald Archive, a collection of over three million photographs. The archive holds work of international, national and local importance by both staff and agency photographers. (Photo by Daily Herald Archive/SSPL/Getty Images)