Harm to humans from radon is greatest:

Question

Quizplus · Accepted Answer

Radon is a radioactive gas that comes from the natural decay of uranium found in nearly all soils. It typically moves up through the ground to the air above and into your home through cracks and other holes in the foundation. Homes trap radon inside, especially well-insulated homes which are more airtight. This can lead to higher concentrations indoors than outdoors, making well-insulated homes potentially more hazardous in terms of radon exposure.

Harm to Humans from Radon Is Greatest