Abstract
The concentrations of potassium, thorium, uranium, and radium, and the relative radioactivity of building materials used in the United Kingdom are described. Particular attention is paid to a potential building material, namely, calcined gypsum prepared as a byproduct in the manufacture of superphosphate fertilizers. The radioactivity of this gypsum material varies according to its origin but is likely to exceed that of any other building material. The wide scale use of this material has to be considered in relation to both somatic and genetic radiation dose of individuals and large populations.