Radon may not concentrate within the body but it does concentrate within unventilated basements and within valleys in granite heavy areas.
It blows away and expresses fresh from the ground on a daily basis such that prolonged exposure is equivilant to a two|three pack a day smoking habit wrt cancer risk.
Radon is much heavier than air (7.5x), so pools in basements. You should be able to keep it cleared out with the gaseous equivalent of a sump pump.
Yep, that's what happens - it pools.
Modern standards in many G20 countries require new (and rennovating) houses in radon prone areas to provide appropriate ventilation.
Geographically in also pools in still valleys, often during the night and morning with radon 'clouds' clearing from the floor by afternoon (as can be seen when processing airborne radiometric survey data and applying radon removal filtering to normalise U-Y-Th maps).
People get cancer when a microscopic grain of Pu lodges in an alveola and just blasts and blasts that one spot for years.