Natural radiation: Radiation exists everywhere, as radioactive elements are part of the Earth and are found in rock, soil, and water.
Lung cancer: Radon exposure is the second biggest cause of lung cancer after smoking.
Nuclear energy: Radioactive elements give off energy that can be harnessed to generate nuclear power, but can also be absorbed by.
Radon poisoning in the past: A Swiss doctor named Paracelsus recorded cases of radon poisoning as far back as 1530.