(Research Center of Bioenvironmental Geochemistry, Chinese Academy of Geological Sciences, Beijing 100037)
Based on the characteristics and sources of radioactive element radon, this paper expounds the influence of radon on the environment and its harm to human body, and points out that to improve people's quality of life and ensure people's health, radon protection must be done from all aspects.
Radon source protection
Radon widely exists in nature and is the intermediate product of three natural radioactive decay series: uranium series, thorium series and actinide series. The decay process of uranium series is 238 u → 226 ra → 222 rn → 210b → 206 Pb, in which the half-life of 222 rn is 3.824 days. The decay process of thorium system is 232Th→228Ra→224Ra→220Rn→208Pb, in which the half-life of 220Rn is 55.6s；; The decay process of actinides is 235 u → 223 ra → 2 19rn → 207 Pb, and the half-life of 2 19rn is 4 s. Because the content of 235 u is very small in nature, the half-life of 2 19rn and its offspring is very short, so it is harmless to human body. 238U and 232Th exist widely in the earth's crust. However, due to the difference of half-life between 222Rn and 220Rn, and the storage of 222Rn in the atmosphere is 0/00 times of that of 220Rn/kloc-,the harm of 220Rn to human body is far less than that of 220Rn. Therefore, in the study of these three natural radioactive decay series, the biological effects of 222Rn and its short-lived daughters formed by uranium series decay are mainly considered, while the decay products of thorium series and actinide series are not considered.
Characteristics and sources of 1 radon
Radon (222Rn) decays from 226Ra, and the half-life of 226Ra is 1602 years, so the content of 226Ra can be considered to be relatively stable. The decay process from 222Rn to 206Pb is as follows:
Geochemical environment: agriculture and health
In which: one year; Landing day; m 1n-min； Microseconds.
The half-life of 2 10Pb is relatively long (22.3 years). From the biological point of view, the short-lived offspring decayed before 2 10Pb mainly irradiated human body.
1. 1 feature
Radon is an inert radioactive element, which does not participate in chemical reactions, but the rays produced by its decay and its daughters are harmful to human body.
(1) Radon and its daughters have strong adsorption. More than 90% of daughters produced by radon alpha decay are adsorbed on aerosol ions in the air and are in a free state. They can be adsorbed by many substances (charcoal, silicic acid, clay, etc.). ), of which activated carbon has the strongest adsorption force and slower sedimentation rate, and the average residence time of adsorbed particles is 1.4 hours.
(2) Radon is soluble in water, fat and various organic solvents. The solubility of radon in fat is 125 times that in water. Therefore, once radon in the air is inhaled into the lungs, it can spread to various tissues of the human body with blood, such as respiratory system, nervous system, blood system, etc., and radon daughters can be detected.
(3) When radon decays, it can emit alpha rays, which can irradiate human body. At the same time, radon and its daughters are difficult to excrete, and the consequence is that human tissues may form tumors.
1.2 Source
Rock, soil, groundwater and other media contain 238U and 226Ra in different degrees, and the regional differentiation is obvious, so the radon concentration produced by this decay is not consistent. These three media contribute greatly to the content of radon in the air and are the main sources of radon. From the distribution range of radon, outdoor radon is mainly provided by rocks, soil, underground (hot) water, mines, coal and other media, while indoor radon is mainly produced by foundation, soil, building materials, domestic water, gas, coal and so on.
The sources of indoor and outdoor radon are discussed as follows.
2 outdoor radon source and variation law
2. 1 source
(1) rock
The content of uranium in the earth's crust and various rocks is different.
Table 1 distribution of uranium in crust and rocks (10-6)
Note: Igneous rocks and crustal abundance are based on vinogradov data of 1962, while sedimentary rocks are based on Tuligan and Weidebo data of 196 1.
As can be seen from the table 1, the uranium content of various rocks varies greatly. The uranium content in shale is the highest in acid rocks and sedimentary rocks of igneous rocks, and the uranium content in ultrabasic rocks is the lowest. The uranium content in metamorphic rocks depends on the uranium content in original rocks. From the point of view of elemental geochemistry, uranium is pro-MagmaElemental, has strong affinity with radon, is composed of oxides, and is easy to be enriched in acidic rocks. In addition, uranium has adsorption; It is often adsorbed by carbonaceous, argillaceous and organic matter, which makes the uranium content in shale, especially carbonaceous shale, higher.
Radon concentration in rocks is not only controlled by uranium (radium) content in rocks, but also depends on rock structure and geological structure characteristics. The areas where faults, fissures and karst systems are developed provide a good channel for radon upward migration, which leads to the increase of radon concentration, and also provides a favorable material source for atmospheric radon, forming a local high radon anomaly in the atmosphere.
There is a large area of granite exposed in South China. According to the main material sources of granite formation, it can be divided into three genetic series: continental crust reconstruction type, syntectic type and mantle source type. Syntectic granites are mainly distributed in the coastal areas of Zhejiang, Fujian and Guangdong. Transformed granites are distributed in the mainland, especially in the coastal areas of western Zhejiang and Fujian and Guangdong, and were formed in the pre-Mesozoic and Mesozoic. The distribution of mantle-derived granite is extremely limited. The uranium content in the reformed granite is generally high, because the strata providing uranium are mainly the Sinian-Cambrian black shale formation rich in uranium, which inherits the uranium-rich in the surrounding rock when the granite was formed, and the content can even reach more than 30× 10-6; However, the uranium content in syntectic granite is much lower (Table 2).
Table 2 Uranium Content of Two Types of Granites in Different Ages in South China
① It belongs to mantle-derived granite.
As can be seen from Table 2, the uranium content of the reformed granite is generally high, and the average content of rocks in each era reaches 13.8× 10-6, with a range of 5.0×10-6 to 24.1×10-6. The uranium content of syntectic granite is generally low. The average uranium content of rock mass in each era is 6.6× 10-6, with a range of 2.5×10-6 ~13.9×10-6. From the Bosi period to the late Yanshan period, the uranium content gradually increased, and the overall uranium content was poor. It can be seen that the uranium content in granite in different times, different producing areas and different regions is different, and the reformed granite is widely distributed with high uranium content. Uranium and its decay products are easy to escape from rocks in fracture and fracture development areas, which leads to the increase of radon concentration in the atmosphere. Therefore, attention should be paid to the distribution of atmospheric radon in this kind of granite area.
In addition, in the south of the Yangtze River, the bottom of the Lower Cambrian is generally composed of black shale, slate and siliceous rocks, and the horizon is stable, which is equivalent to Zhalagou Group in Guizhou and Tanghe Formation in Zhejiang. Rock layers vary in thickness (30 ~ 30 ~ 300m), with high carbon content and many metals and rare elements, especially in eastern Guizhou and western Hunan. It is formed in the environment of reduction and stagnant water flow, and belongs to marine deposition. In the process of its formation, submarine volcanism is frequent, and a large amount of phosphorus is dissolved in sedimentary basins, accompanied by elements such as V, Co, Mo, Ni and Cu. Phosphorus has a large ion radius and is easily replaced by large ions such as uranium, forming a * * * relationship. At the same time, carbon has great adsorption, which promotes the enrichment of rare metals such as uranium. When the carbon content exceeds the standard of carbonaceous shale, a stone coal seam is formed. For example, in eastern Guizhou, western Hunan, northwestern Jiangxi, southern Anhui and western Zhejiang, stone coal seams are widely distributed in Hunan, Hubei, Guangxi and northern Guangdong. Because local people use carbon slate and carbon shale to burn bricks, they can save 30% of fuel and release uranium, resulting in high radon concentration in the air, which is the main factor for the high incidence of lung cancer in the local area. Another factor is the application of phosphate rock resources in agriculture, which makes uranium (radium) enter the human body through crops, producing internal radiation and leading to lung cancer. These factors should be highly valued by relevant departments.
From the point of view of element migration and transformation, the radon concentration in the air depends on the radon concentration in rocks and soil, while the radon concentration and soil radon in rocks depend not only on the uranium content in the parent material, but also on the structural characteristics of rocks. The uranium content in rocks is high, and the radon concentration is high when fractures develop. When the fracture is not developed, even if the uranium content in the rock is high, the radon concentration may not be high because of the lack of uranium migration channels. Therefore, we should first find out the distribution of uranium-bearing rocks and uranium elements, then understand the rock structure and fracture development, and finally discuss radon concentration.
(2) Soil
Radon in the air mainly comes from radium in the soil. Soil is the product of rock weathering. Because of the different contents of uranium and radium in rocks, the contents of uranium and radium in soil are also different, which have similar distribution laws with rocks. 226Ra in soil is generally10 ~100bqkg-1,and the emissivity of 222rn is 16mbq m-2 s- 1. It is assumed that radon gas exists in the ground 1 ~ 3 km, and the radon concentration in the surface air is about 2.7 bq m-3.
(3) Underground (hot) water
The enrichment degree of radon in groundwater mainly depends on the radium content of rocks and the emanation coefficient of rocks during water circulation. With the development of cracks in rocks, the emanation coefficient can be greatly improved, which will lead to the enrichment of radon in water.
The radon concentration in fissure water of acid intrusive rocks and eruptive rocks in China mostly exceeds100 bq l-1,with an average value of 210bq l-1and a range of10.3 ~1470bq.
The radon concentration in water in sedimentary rocks is low, generally less than 200 bq l-1,and the radon concentration in water in rocks accounting for 50% ~ 80% of the total is less than 45 bq l-1. The average content of radon in clastic rocks such as sandstone and conglomerate is 40bq L-1,and the range is 0.81~ 355bq L-1. The average radon content in carbonate aquifer is less than 45bq L-1,and the range is1.59 ~143.4bq L-1.
The radon content in groundwater in metamorphic rock area fluctuates greatly, and varies with the content of radioactive elements in rocks, with an average value of 90bq L-1,ranging from 0.007 to 232.5bq L-1,and less than 45bq L-1accounts for about 40%o of the total.
It can be seen that the lithologic selection order of radon enrichment in groundwater is: acid rocks (including extrusive rocks) → metamorphic rocks → carbonate rocks, sandstone and conglomerate. In terms of regional distribution, the abnormal areas of radon content in groundwater in China (> 135 bq L- 1) are mainly distributed in acidic magmatic rocks (especially granite) such as the southeast coast (Fujian, Guangdong, Hainan and other provinces), northern Hunan, southern Hubei, western Henan, Liaodong Peninsula and Shandong Peninsula, indicating that high uranium content in rocks provides radon for groundwater.
After groundwater flows out of the ground, radon dissolved in the water will quickly spread into the air, and it is estimated that about 30% ~ 90% of radon in the water will enter the environment.
(4) Mining
In the 20th century, people gradually realized the radon problem caused by uranium mining and non-uranium mining. At the end of 16, Germany reported for the first time that uranium miners died in mine accidents, with a very high mortality rate. It was not until late 19 that the cause of death was pulmonary malignant tumor. Since 1930s, the competent authorities began to pay attention to the occupational diseases of uranium miners, and also carried out underground radon monitoring. After World War II, until 1950s and early 1970s, the incidence of lung cancer rose sharply due to the massive exploitation of uranium. After 1980s, underground working conditions around the world have been significantly improved. Epidemiological studies show that there is a positive correlation between lung cancer and cumulative exposure WLM of radon in miners.
The level of radon daughters in uranium mines in China is generally in the range of 0.22 ~ 1.4 WL, and most of them exceed the standards stipulated in China. In recent years, due to the adoption of ventilation and radon reduction technology and monitoring and protection work, the working conditions of uranium mines have been improved. Compared with foreign countries, the lung cancer problem of uranium miners in China is not very prominent. However, it should be noted that the number of lung cancer patients in non-uranium mines in China has increased since the early 1960s. Since 1980s, the annual death toll has reached 80 ~ 100, which is a high incidence area of lung cancer. The average underground radon concentration is 28.80 kbq m-3, and the cumulative exposure of miners is estimated to be 65433.
The main sources of radon in uranium deposits are exposed uranium ore bodies, uranium ores and radon precipitates in groundwater. Non-uranium mines generally have no uranium ore bodies or only a few sporadic uranium ore bodies, and most of them contain a very small amount of uranium (radium) in surrounding rocks and ore bodies, but they become the main source of radon because of their large exposed area. In addition, mined-out areas and abandoned tunnels will become the main channels for radon escape.
(5) burning coal
Coal is the product of strong reducing environment, which contains a lot of organic components and high contents of uranium and radium. According to the measurement, every burning of 1kg coal can produce 36Bq of 222Rn, so burning coal is an important source of radon pollution in urban environment. The total amount of radon pollution provided by power plants and northern areas in winter can not be underestimated. For example, the coal in Tianjin is used in industry, family and institutions. And calculate that the total radon pollution in the atmospheric environment can reach 560GBq per year; The fuel structure in Beijing is dominated by coal, with an annual consumption of 28 million tons, and only 8 million tons of coal is used for heating in winter. Coupled with automobile exhaust emissions, air pollution (especially in urban areas) is very serious. There are four months in a year when the air quality is above Grade 4, and the visibility in winter is worse than other seasons, which is the high incidence period of respiratory diseases. Burning coal not only produces a large amount of sulfur dioxide and radon, but also its floating dust becomes a carrier of a large number of viruses, bacteria and microorganisms, which are easily deposited in human lungs and endanger human health.
2.2 Change the law
(1) Seasonal concentration changes. The survey results of provinces and cities in China are basically the same: the maximum value appears in winter, the minimum value appears in summer and the annual average value appears in spring and autumn. The radon concentration in the ambient air depends on the radon exhalation rate on the ground and its migration and diffusion in the atmosphere. In winter, the temperature is low, and coal-fired heating (especially in northern cities) is an important reason for the high radon concentration in the atmosphere.
(2) the change of the height from the ground. Radon concentration in the atmosphere decreases with the increase of troposphere height. Assuming that the radon concentration at 0.0 1m from the ground is 100%, the radon concentrations at 1 0, 100, 1000 m are 95%, 87% and 69% respectively. Under the condition of natural ventilation, the indoor radon concentration also has the same law, that is, the indoor radon concentration in bungalows is higher than that in high-rise buildings.
(3) The influence of atmospheric pressure. Air pressure is negatively correlated with radon release in soil and other media. When the air pressure decreases, the emissivity of radon in the medium increases and the concentration of radon released into the air increases. Generally speaking, if the air pressure is reduced by 1%, the radon emissivity can be doubled.
To sum up, there are many factors affecting environmental radon, and the regional differentiation of radon is obvious, and environmental radon in different regions presents different characteristics. When discussing the problem of radon, we should combine the local actual situation.
Indoor radon
Because people spend most of their time working, studying and living indoors, it is extremely important to know the indoor radon concentration and its distribution. Indoor radon concentration is closely related to geological environment, building materials, coal (gas) and water.
3. 1 Geological environment
According to the research results of Qingdao, Beijing and other places during the Eighth Five-Year Plan period, it is found that the geological factors affecting indoor radon are mainly bedrock lithology and weathered soil and structural faults.
Table 3 Average level of soil radionuclides in Qingdao (bq kg- 1)
Table 4 Comparison of indoor radon concentration in some areas of China (BQ m-3)
The Yanshanian magmatism in Qingdao area was frequent, forming large-scale granite intrusions, with thin surface coverage and many houses built on bedrock. Therefore, the level of radionuclides in granite in this area is higher than that in Shandong Province and the world (Tables 3 and 4).
According to Table 3, except for 137Cs, the levels of other radionuclides in Qingdao are higher than those in Shandong Province and the world in different degrees, and the level of soil radionuclides is determined by its bedrock, indicating that the content of radionuclides in granite is high. Radon is directly decayed from uranium (radium), and high radionuclide content affects radon concentration, so it shows the characteristics of high value. As can be seen from Table 4, although the rooms in Qingdao are well ventilated, the indoor radon level is still higher than the average level in China and many cities in the world. The average absorbed dose rate of air radiated by Rock 7 is 22.6×10-8 Gy h-1,which is higher than the national level (8.15×10-8 Gy h-6544).
If a house is built in an area with high radon concentration, its indoor radon concentration is bound to be high. In most cases, the foundation under buildings is the main source of indoor radon. Radon gas in soil can enter the room through various channels such as soil pores, foundation cracks, wall cracks and pipeline cracks, which leads to the increase of radon concentration in the air. If the foundation is untreated soil ground, radon is easy to accumulate indoors, and the radon concentration diffused indoors under cement ground is 5 ~ 20 times weaker than that without ground.
3.2 Building materials
The content of radionuclides in building materials varies greatly with the types and regions of building materials. Generally speaking, the content of wood products, plaster of Paris, metal and cement is low, while the content of industrial by-products such as granite, pumice, clay brick, artificial gypsum, fly ash from thermal power plant and concrete made from industrial waste residue is high. According to the measurement in Chenzhou, Hunan Province, the indoor radon concentration of houses built with stone slag bricks with radium content as high as 34 1bq kg- 1 has reached 473 ~1310bq m-3, which has greatly exceeded the national standard. Hong Kong 1993 reported that the indoor radon concentration reached 280 bq m-3 due to the use of local granite with high radium content. In fact, when the radium content in building materials exceeds 500 bq kg- 1, building materials radon becomes the main source of indoor radon.
Our center has measured the radon concentration of buildings made of carbonized bricks and other building materials in Huangshan area of Anhui Province 1994 ~ 1995. The statistical results are shown in Table 5.
Table 5 Average indoor radon concentration in Huangshan area (BQ m-3)
Note: All samples are determined by the Ministry of Health.
Carbonized bricks in Huangshan area are made of local lower CAMBRIAN carbonaceous shale and slate. Because of the high uranium content in this kind of rocks, the indoor radon concentration of houses built after brick burning exceeds the background value, ranging from 78 to 331.4 bq m-3. In the same area, the indoor radon concentration of houses built with different building materials is different. For example, the indoor radon concentration of the carbonized brick house in Lantian is 1.8 times that of the blue brick house, and that of the hollow brick house in Yixian is 1.3 times. It is worth noting that the indoor radon concentration in bungalows or houses with civil structures is also very high. This is because the radon concentration in the local soil is high, and there is no obstacle for radon to enter the room, which makes the radon concentration in the air even higher than that of houses built with carbonized bricks. It can be seen that the type of building materials has a great influence on indoor radon concentration.
1986, the environmental protection agency of the United States (EPA) set the indoor radon action level as148bq m-3 (4pci l-1), but the indoor radon concentration in buildings such as carbonized bricks and adobe houses in Huangshan area is generally higher than or close to the radon action level, so the health department should take necessary intervention measures.
3.3 Domestic water
Radon has a certain solubility in water. Because the half-life of radon is 3.824 days, most radon has not decayed before tap water enters the living room from the management road of the water plant. Therefore, the release of radon in water is also a factor to provide radon indoors. If domestic water comes from underground, it is more likely that radon concentration in water is higher than that in surface water. When the radon concentration in water is greater than10 kbq m-3, the influence of water on indoor radon concentration can not be ignored.
3.4 Coal and natural gas
Coal and gas (natural gas, liquefied petroleum gas, coal-to-gas) contain high concentrations of uranium and radium. Coal is still the main fuel in rural areas and towns in China, and many cities have switched to natural gas as energy. After mixed transportation, the radon content in the natural gas at the production wellhead is about 0 ~ 50 kBq m-3, and the radon content in the pipeline is about 0.04 ~ 2 kBq m-3. If the radon content in the pipeline is1kbq m-3-3, assuming that 2m3 gas is used every day, 2000Bq radon gas can be discharged indoors. The changes of uranium and radium in liquefied petroleum gas and coal-to-gas are basically the same as those in natural gas.
To sum up, the media that cause indoor radon pollution are mainly soil and building materials. If the house is well ventilated, indoor air can be exchanged with outdoor air, and radon concentration can be reduced to atmospheric radon level; On the contrary, the use of air conditioning equipment, thermal insulation materials or circulating air in the living room makes the living room in a relatively closed environment, and indoor radon cannot be discharged outside in time. The decrease of ventilation rate will increase radon exposure by 2 ~ 8 times, thus greatly increasing the incidence of lung cancer.
Harm and protection of radon and its daughters
4. 1 Harm of Radon and Its Daughters
The results show that the proportion of inhaled radon is greater than that of human consumption, and the harm of radon daughters to human body is greater than radon itself. After radon daughters enter the lungs from the respiratory tract in the form of aerosol, most of them are deposited in the lungs, and a few can be excreted upward through the trachea. Substances with high solubility are dissolved by interstitial fluid and enter the blood through alveolar membrane, and insoluble particles can also directly enter lymph nodes and blood without any intermediates. According to the ICRP (International Commission on Radiological Protection) "Lung Model" experiment, 80% of the particles of 10μm are trapped in the nasopharynx, almost all the particles of 3 ~ 5μ m are trapped in the upper respiratory tract, and 90% of the particles of1.5 μ m are trapped in the lung bronchus, and the particles with smaller diameter can be inhaled into the deep respiratory tract. After radon and its daughters enter the human body, they emit A rays, which make the human body receive a certain amount of internal radiation dose. Because people stay indoors for a long time, indoor radon concentration is higher than outdoor, and the natural radiation dose of radon and its daughters in indoor air is much higher than outdoor.
The Environmental Protection Agency (EPA) estimates that the number of deaths caused by indoor radon exposure is 7000 ~ 30000 every year, which is second only to drunk driving and higher than that caused by drowning, fire and plane crash. If smoking is combined, the radon risk of smokers is 15 ~ 20 times that of non-smokers. The International Agency for Research on Cancer (IARC) recognizes that radon and its short-lived daughters are human carcinogens without thresholds.
4.2 Radon Daughter Exposure Limit and Radon Action Level
In order to reduce the harm of radon and its daughters to human body, China and the world have formulated corresponding standards.
For mines, the British NPRB (National Radiation Protection Agency) suggested limiting the exposure of radon in caves and abandoned mines, and put forward the age value of106 bq m-3h (222 rn, balance coefficient of 0.4), which is equivalent to 1WLM. 198 1 year ICRP-32 report is set at 4.8WLM per year, which is adopted by GB4792.84 and GB8703.88 in China. According to the epidemiological data in ICRP-65 report 1993, it is determined that miners work for five years, with an average of 4WLM per year (consistent with the value of 197 1 year), that is, they work for 2000 hours per year, and the balance coefficient is 0.4, which is equivalent to 3000 bq L- 1 year. If they work for a year,
For indoor radon, Britain first put forward the concept of action level in 1987, that is, when the indoor radon concentration exceeds the action level, the householder should take immediate action to reduce the radon concentration. To this end, many countries in the world have formulated corresponding standards (Table 6).
Table 6 International Indoor Radon Control Level (BQ m-3)
In addition, China formulated the Hygienic Protection Standard for Underground Buildings and Geothermal Water in 1996: the function level of existing underground buildings is 400 bq m-3, and the upper limit of underground buildings to be built is 200 bq m-3; The control level of radon in civil geothermal water is 50kbq m-3, industrial water is100kbq m-3 and medical water is 300kbq m-3.
4.3 Radon protection
In order to reduce the inhalation of radon and its daughters into human body, it is necessary to reduce the concentration of radon in the air, and the key to the problem is to reduce the concentration of radon released by materials providing radon sources as much as possible, and take different measures to prevent and reduce radon according to the actual situation.
In uranium and non-uranium mining areas and underground places, radon and its daughters can be effectively reduced by improving ventilation system, installing radon reduction and dust removal equipment and cooperating with radon monitoring and protection. For example, after strengthening radon control in France, the average concentration of underground radon daughters decreased from1971~18wl in 0973 to 0.1wl in 1975.
In medical and industrial units that use geothermal water and hot spring water, staff should strengthen their awareness of self-protection with reference to occupational protection limits, and wear efficient protective masks when necessary. There are many ways to reduce radon in the workplace, such as local ventilation; Pipeline water seal recycling; Radon is driven out of water by heating and artificially separating radon from water; Radon and its daughters can be adsorbed by activated carbon and ultrafiltration membrane filtration and adsorption devices. Can achieve the purpose of reducing radon and removing radon.
Indoor radon pollution is something that all the public should be concerned about. In the residential area to be built, we should first investigate whether the area is a high radon distribution area and choose a low radon area as the building base. If you can't avoid high radon areas, you should use bricks and building materials with low uranium and radium content as much as possible, and the floor of the house should use materials with good sealing performance. For example, cement floor has better radon prevention effect than wood floor, and possible gaps in walls, floors and pipelines should be sealed with materials to block radon from entering the room; In the built houses, methods such as window ventilation, mechanical ventilation (such as ventilator and electric fan), air purifier and air freshener should be adopted. Even in air-conditioned rooms, windows should be opened regularly for ventilation. When gas or coal is used, a ventilator or a range hood should be used at the same time to discharge radon and lampblack outdoors. In short, indoor and outdoor air should be exchanged regularly to reduce indoor radon pollution.
The United States, Britain, Canada and other countries launched a large-scale indoor radon survey in the 1990s, which played a positive role in promoting indoor radon protection. The work of indoor radon in China has just started. 1In June 1995, the Ministry of Health and the Ministry of Geology and Mineral Resources jointly established the "Leading Group for Radon Monitoring and Prevention", which will be responsible for coordinating the national radon transfer survey, indoor radon monitoring, radon hazard assessment, radon prevention research and consultation, collecting relevant information and carrying out regional and international cooperation. Therefore, it will greatly promote indoor radon prevention in China, improve the quality of life and protect public health.
In the process of writing, this manuscript has been strongly supported and helped by Zeng senior engineer and Huang Huaizeng researcher. Thank you very much!
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