Population doses from terrestrial gamma exposure in China

In order to estimate terrestrial gamma radiation exposures, three nationwide surveys have been completed since 1981. The population weighted outdoor and indoor arithmetic means of gamma dose rates based on momentary measurements using a NaI(T1) environmental radiation meter and a high pressured ionization chamber are 80.3 and 120 nGy.h-1. The means based on integrating measurements using TLD natural radionuclides concentrations in soil, determined by gamma spectrometry analyses, are 72.8 and 102 nGy.h-1, respectively. These surveys were conducted independently and equally representative. The best estimation of site-averaged and population weighted gamma dose rates in China, based on all these surveys, would be 70 and 98 nGy.h-1 for indoor and outdoor, respectively. The annual average of effective dose equivalent is 0.56 mSv. These values are higher than the world averages estimated by UNSCEAR. The main reason is that the concentrations of 232Th and 40K in soil of China are much higher than the world average estimated. (author). 4 refs, 2 tabs