Radiation was discovered in the late 19th century. However, people were not initially aware of the damage radiation exposure and radioactive rays could cause.
The acute effects of radiation exposure were first seen in 1896 when Nikola Tesla purposefully subjected his fingers to X-rays and reported that this caused burns to develop, although at the time he attributed the burns to ozone.
The mutagenic effects of radiation were not realized until decades later. The genetic effects and increased cancer risk associated with radiation exposure were first recognized by Hermann Joseph Meller in 1927. Muller went on to receive the Nobel prize in 1946 for his research.
However, before these effects were understood, many radioactive substances had already been marketed by corporations and various physicians. Examples included radium enema treatments and radium-containing water tonics. It was Marie Curie who protested against these therapies and pointed out that the effects of radiation exposure were poorly understood. Radiation poisoning was the cause of the aplastic anemia that eventually killed Curie.
In 1932, a famous American socialite called Eben Byers died after ingesting large amounts of radiation over the course of several years. This death and many others among radiation enthusiasts sparked intrigue over the effects of consuming radiation-containing products and they were eventually removed from the market.
The gravity of the effects caused by radiation were not fully understood until the 1940s. Two scientists from the USA died in 1946 after working with fissile materials without using protective clothing or shielding. The Hiroshima bombing also caused wide-scale radiation poisoning and the actress Midori Naka, present during the bombing, was studied extensively for radiation poisoning. Her death in 1945 was the first to be officially documented as having been caused by radiation poisoning. At the time, this radiation poisoning was referred to as Atomic bomb disease.