| There is Radioactive radon and radon daughters in people's living environment. Since the recent half century, the danger of radon has got a wide range of concerns and researches on the potential harm that radon and its daughters may do to human body, which has become more and more. With the development of society and improvement of people's quality of life, people's living habits are changing. The extensive use of air conditioner lowers the efficiency of ventilation and gas exchange indoor, which increases the potential hazards of radon radiation pollution. This topic is based on two projects, the research (No.40374051) on Earth-to-air interface radon and its effects on Environmental radiation in National Natural Science Foundation and the survey about levels of national indoor radon concentration. Radon is the main source of natural radiation human suffers from. Radon and its daughters is announced as one of 19 the major environmental carcinogens by WHO (World Health Organization). The public dose caused by radon and its daughters and its bad effect on health have attracted attention from all over the world. Recent studies show that the indoor radon concentration in some domestic cities is rising. In order to get a comprehensive understanding of the situation of the indoor radon concentration levels in Chengdu, the indoor radon concentration levels and gamma dose rates of different types of housing in Chengdu city were measured and analyzed. This essay classifies the measured data and analyzes the major factor that influences the indoor radon concentration levels in Chengdu city.This paper discusses the dangers, the source, basic nature and measuring means of radon. It classifies and selects measured houses according to the proportion of people in the county, housing types, building ages and building structures in Chengdu Statistical Yearbook in 2006. The indoor radon concentrations andγradiation levels in selected houses are surveyed by means of solid state nuclear track detector(SSNTD' s) and thermo luminescence dosimeter(TLD).The results were counted and analyzed and factors affecting the radon concentration are discussed in this essay. Finally, the residents'effective dose caused by the inhalation of internal radiation of radon and external irradiation of Y radiation were estimated.According to 234 groups of survey data: the highest level of indoor annual average radon concentration in Chengdu is 177.1 Bq/m3, the lowest level is 8.4Bq/m3,, and the average level is (39.4±22.9) Bq/m3. When analyzing various types of housing, we easily found that there are apparent differences among different types of buildings in the indoor radon concentration levels. The indoor radon level of houses made of new building materials after 2000 are significantly higher than that of the buildings made of bricks and woods. The average level of indoorγradiation in Chengdu is 122.1 nGy/h, which is not concerned with indoor radon concentration.The annual average effective dose caused by the 222Rn inhalation and its daughters of the Chengdu residents is 0.79mSv, and the annual average effective dose caused byγ-ray irradiation is 0.48mSv. The total amount of the annual average effective dose caused by the radon inhalation andγ-ray irradiation of the Chengdu residents is about 1.27mSv, which is below the world average annual effective dose of 2.4mSv The survey found that the general level of indoor radon concentration in Chengdu was below the national recommended limits. But, in some houses, the indoor radon concentration was as high as 177.1 Bq/m3, which is close to the national recommended limits 200 Bq/m3. This fact should be paid much attention to prevent the continue rise of indoor radon concentration. Chengdu indoor radon comes mainly from building materials. The use of new building materials after 2000 years is the main course of the rise of indoor radon concentration in Chengdu. Residents here inhale 0.79mSv effective dose of 222Rn and its progeny annually, while the effective dose ofγradiation is 0.48mSv every year. The sum of inhalation of Gifthauch and the exposure to radiation of Chengdu citizen is about l.27 mSv, which is below the world average effective dose of 2.4 mSv annually.
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