Health assessment of natural radioactivity and radon exhalation rate in granites used as building materials in Lebanon

Measurements of specific activities (Bq kg(1)) of gamma-emissions from radioactive nuclides, U-238, Ra-226, Bi-214, Th-232, Pb-212 and K-40, contained in 28 granite types, used as building materials in indoors in Lebanon, were performed on the powdered granites. The concentration of the nuclides, Ra-226, Th-232 and K-40, in the granites varied from below detection level (BDL) to 494 Bq kg(1), BDL to 157.2 Bq kg(1) and BDL to 1776 Bq kg(1), respectively. Ra-226 concentration equivalents, C-Raeq, were obtained and ranged between 37 and 591 Bq kg(1), with certain values above the allowed limit of 370 Bq kg(1). Calculated annual gamma-absorbed dose in air, D-aR, varied from 17.7 to 274.5 (nGy h(1)). Annual effective dose, E (mSv y(1)), of gamma radiations related to the studied granites and absorbed by the inhabitants was evaluated. E (mSv y(1)) ranged from 0.09 to 1.35 mSv y(1). Some granite types produced E above the allowed limit of 1 mSv y(1) set by ICRP. Values of Rn-222 mass exhalation rate, E-M (mBq kg(1)h(1))(,) in granite powder were obtained using the CR-39 detector technique. Diffusion factors, f, in 23 granite types were calculated with f ranging between (0.10.02)10(2) and (6.61.01)x10(2).