Radiological hazards for marble, granite and ceramic tiles used in buildings in Riyadh, Saudi Arabia

²²⁶Ra, ²³²Th and ⁴⁰K activity concentrations have been determined by gamma-ray spectrometry in different types of marble, granite and ceramic tiles that are commonly used for interior and exterior purposes in buildings in Riyadh, Saudi Arabia. Marble showed the lowest concentrations of the three measured radionuclides, while the highest ²²⁶Ra and ⁴⁰K activities were found in granite and the highest ²³²Th concentration was found in ceramic samples. Activity measurements were used to calculate the elemental concentrations of uranium and thorium and to assess the associated radiation hazards by evaluating various radiological hazard indices, such as radium equivalent activity, external and internal hazard indices and gamma and alpha radiation indices. Moreover, the absorbed gamma dose rate in indoor air, annual effective dose equivalent and annual gonadal dose equivalent were also presented. In most cases, the calculated parameters showed levels below the permissible limits indicating the safe use of these materials for building constructions. The relative contribution of the natural radionuclides to the radiation dose in the studied materials as well as the hazard portion due to exhaled radon was also estimated. The lifetime risk assessment from exposure to gamma sources in the investigated samples showed values in the range of 10⁻⁴–10⁻³.