Radioluminescent paint was invented in 1908 by Sabin Arnold von Sochocky and originally incorporated radium-226. Radium paint was widely used for 40 years on the faces of watches, compasses, and aircraft instruments, so they could be read in the dark. Radium is a radiological hazard, emitting gamma rays that can penetrate a glass watch dial and into human tissue. During the 1920s and 1930s, the harmful effects of this paint became increasingly clear. A notorious case involved the "Radium Girls", a group of women who painted watchfaces and later suffered adverse health effects from ingestion. In 1928, Dr von Sochocky himself died of aplastic anemia as a result of radiation exposure. Thousands of legacy radium dials still owned by the public and the paint can still be dangerous if ingested in sufficient quantities, which is why it has been banned in many countries.