Which radioactive pollutant has recently drawn the attention of the public, due to its occurrence in the building material ?

Radon has recently attracted public attention because it can emanate from building materials and accumulate indoors, posing a proven lung-cancer risk. Radioactive pollutants listed in environmental texts include radon and radium, with radon singled out as an indoor hazard that affects respiratory health [1]. Authoritative reviews and monographs explain that radon-222 is produced by decay of uranium and thorium in rocks and materials; it seeps from soils and some construction materials into confined spaces, making indoor radon a controllable but significant source of population exposure [2]. For these reasons, radon (option 3) is the radioactive pollutant of public concern in buildings.

Sources

1. [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Consequences of Air Pollution > p. 40
2. [2] https://www.ncbi.nlm.nih.gov/books/NBK316369/