Radon emits a particles. The main hazard is from inhalation of the element and its radiodecay products which collect on dust in the air. This might be a hazard in, for instance, uranium mines. Recently, radon buildup in homes and cellars from the surrounding soil and rocks has become a safety issue and some areas around the world test homes for radon gas. Part of the problem is that it is the heaviest known gas.
Radon is present in some spring waters.
Chemically, radon gas is not a hazard.