GAMMA ACTIVITY IN LAHORE - PAKISTANI BUILDING-MATERIALS

Natural radioactivity due to K-30, Ra-226, and Th-232 has been measure d, using a HPGe (high purity germanium) based gamma-ray spectrometer, in samples of unbaked clay bricks, sand, cement, aggregate or crush, m arble chips, and glass used for the construction of dwellings in the c ity of Lahore (Pakistan). The radium equivalent activities and hazard indices have been determined for these materials. The maximum value of the radium equivalent activity is 319 +/- 10 Bq kg-1 in ceramics, whi ch is less than the normally accepted limit of 370 Bq kg-1. The maximu m values of hazard indices are also less than unity except for some ce ramic samples. Therefore, the materials used for the construction of d wellings in Lahore do not pose a major gamma-ray hazard. The dose equi valent rate due to gamma-rays at the centre of a standard size room is theoretically determined. Our calculations show that the gamma-dose e quivalent rate is smaller by a factor of 2.5 if the buildings are made from concrete rather than from clay bricks.