sentences:  The new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine (as had the discoveries of electricity and magnetism, earlier), and a number of patent medicines and treatments involving radioactivity were put forward.Gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long-term hazard.Many of the scientists working on radioactivity died of cancer as a result of their exposure.