| Purpose Radon is the main source of natural radiation exposure to public,the lung cancer caused by radon exposure in the living environment is considered as one of the global burden of diseases.Recent studies reveal that indoor radon concentrations have increased in some large and medium-sized cities in China, particularly in Shanghai.For more comprehensive understanding of the leveI of indoor radon and the reason of increasing in Shanghai,measurements and analysis of indoor radon concentrations were carried out in different types of houses in this study. Moreover,the radon exhalation rates of some typical building materials were also studied to explore their influence on indoor radon level in Shanghai.Methods Based on Shanghai Statistical Yearbook 2006,a total of 211 dwellings were selected for measurements according to the proportion of the population in different districts,building types,building ages and so on.The passive radon/thoron discriminative monitors and the thermoluminescent dosimeter were used to measure the levels of indoor radon and gamma radiation,respectively. Measurements of radon lasted for one year in a consecutive period of three months, and the gamma radiation were only measured in one period.Having statistically processed and analyzed the measured results,the annual effective doses from indoor radon exposure and gamma radiation were estimated by the methods recommended by UNSCEAR in 2000.The radon exhalation rates of the commonly used building materials were measured with the static accumulation method for estimating indoor radon concentration in Shanghai.And some influencing factors were also analyzed for studying their influence on radon exhalation.The impact of building materials on indoor radon concentration was analyzed by comparing the estimated results with the measured values.Results The annual indoor radon concentrations in Shanghai were observed in a range from 6 to 95 Bq·m-3,with an arithmetic,a geometric and a median values of (25.3±14.7),(22.3±1.6) and 21 Bq·m-3,respectively.The averaged indoor gamma radiation in Shanghai was found to be 0.13μGy·h-1.Statistical analyses showed that the differences of indoor radon concentrations in different types of buildings were significant,however,no significant correlation was found between the radon concentration and the gamma radiation.The total annual effective dose estimated for the resident in Shanghai from indoor radon exposure and gamma radiation was 1.28 mSv.The exhalation rate of aerated concrete blocks was higher than the concrete blocks or fired perforated bricks.The estimated results with the measured values show that radon concentration in the building constructed with aerated concrete blocks and the concrete blocks was higher than those constructed with fired perforated bricks.Conclusion None of the dwellings in this study was observed with indoor radon concentration exceeded the national recommended action level.However,the annual average of indoor radon concentrations was significantly higher than that observed 1980s.The main contributor of indoor radon in Shanghai is building materials.The difference of building materials used before and after the year of 2000 is one of the main reasons for the increase of indoor radon concentration in Shanghai.
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