Radon is a decay product of Uranium, which has 92 protons. Lose six and you get Radon. Lose four more and you quit with Lead (82). Radon (86) decays into Polonium with 84 protons. Polonium is what Marie Curie found in pitch blend, she named it after her native Poland, but her exposure to it gave her leukemia and killed her... after she was the first to ever get a Nobel in Chemistry and Physics! Polonium releases alpha particles, two protons and two neutrons, a Helium nucleus. They attach to dust and we breathe them in and our lung tissue does not get along well with them. Average indoor radon level is 1.3 picocuries/liter. ( Normal outdoor levels are about 0.4.)
Remediation is recommended in the US at 4.0 picocuries/liter mainly because improving ventilation can reduce this to around 2. In Europe they remediate at 7. Typical remediation involves adding a passive or powered vent pipe to your sump and venting it above your living space. Permanent radon monitors are available at reasonable cost. Use "detectors" tag on this website.
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