Radon exhalation rates from zircon sands and ceramic tiles in Italy.

Naturally occurring radionuclides in building materials are sources of external and internal exposure in dwellings. External radiation exposure is caused by the gamma radiation originating from members of uranium and thorium decay chain and from 40K. Internal radiation exposure, mainly affecting the respiratory tract, is due to the short-lived daughter products of radon which are exhaled from building materials into room air. The objective of this study is to measure the radon exhalation rates from zircon materials, flours and sands, used as raw materials in the porous fired tiles body and from the final products (porcelain tiles usually commercialized in Italy). The radon exhalation rates for the zircon flours and sands ranged from 0.17 to 1.9 Bq kg−1 h−1, and from 0.090 to 0.20 Bq kg−1 h−1; 222Rn exhalation rates for most of the porcelain stoneware tiles are near or below the minimum detectable limit (LLD) of 0.0004 Bq kg−1 h−1.