Everyone is at risk without exception.
In addition more concern goes towards children whose lungs are still developing and those who spend long times in their home, for instance because they have a home office in their basement or for any other reason..
If I would look for excluding groups I could make a case that people living in boat- and tree-homes and people living above the third floor in residential structures most likely are not subject to elevated levels of radon during the times they stay in these places. Although I am aware of rare exceptions to this rule also.