Radium was famously found by the Curies, and was once widely used in face creams, drinks and luminous watch dials, despite being highly radioactive, says Allan Blackman in ep 68 of Elemental.

Radium was first isolated as an element from pitchblende by Marie and Pierre Curie in 1898, just two years after Henri Becquerel discovered radioactivity, although the dangers of radioactivity were not recognised at that time.

Radium salts glow in the dark and were infamously used on luminous clock and watch dials in the early twentieth century. The workers who painted the dials, later known as the 'Radium Girls', were encouraged to lick the tips of their paint brushes and later successfully sued their employer when many of them began dying from cancer and radiation-induced illnesses.

Radium was also added to water, coffee, beer and even face creams, before its dangers were realised.

Radium is dangerous to humans because it behaves similarly in our bodies to calcium, says Professor Allan Blackman from the Auckland University of Technology in episode 68 of Elemental.

Go to this episode on rnz.co.nz for more details