Population dose in the vicinity of old Spanish uranium mines

Regional surveys were conducted to determine exposure to natural sources of radiation for people in the vicinity of old Spanish uranium mines. The surveys evaluated indoor radon concentrations and outdoor and indoor external gamma dose rates. Indoor radon concentrations were measured in 222 dwellings by means of nuclear track-etched detectors. The terrestrial gamma ray dose rate was measured outdoors and indoors at a total of 256 points and 115 points, respectively. Estimates mean annual effective doses for the six areas studied ranged from 3.2 to 5.1 mSv per year, which is between 1.2 and 2 times higher than the average national value.     

The Iowa radon lung cancer study--phase I: Residential radon gas exposure and lung cancer

Exposure to high concentrations of radon (222Rn) progeny produces lung cancer in both underground miners and experimentally-exposed laboratory animals. The goal of the study was to determine whether or not residential radon exposure exhibits a statistically significant association with lung cancer in a state with high residential radon concentrations. A population-based, case-control epidemiologic study was conducted examining the relationship between residential radon gas exposure and lung cancer in Iowa females who occupied their current home for at least 20 years. The study included 413 incident lung cancer cases and 614 age-frequency-matched controls. Participant information was obtained by a mailed-out questionnaire with face-to-face follow-up. Radon dosimetry assessment consisted of five components: (1) on-site residential assessment survey; (2) on-site radon measurements; (3) regional outdoor radon measurements; (4) assessment of subjects' exposure when in another building; and (5) linkage of historic subject mobility with residential, outdoor, and other building radon concentrations. Histologic review was performed for 96% of the cases. Approximately 60% of the basement radon concentrations and 30% of the first floor radon concentrations of study participants' homes exceeded the US Environmental Protection Agency action level of 150 Bq m(-3) (4 pCi l(-1)). Large areas of western Iowa had outdoor radon concentrations comparable to the national average indoor value of 55 Bq m(-3) (1.5 pCi l(-1)). Excess odds of 0.24 (95% CI = -0.05-0.92) and 0.49 (95% CI = 0.03-1.84) per 11 WLM(5-19) were calculated using the continuous radon exposure estimates for all cases and live cases, respectively. Slightly higher excess odds of 0.50 (95% CI = 0.004-1.80) and 0.83 (CI = 0.11-3.34) per 11 WLM(5-19) were noted for the categorical radon exposure estimates for all cases and the live cases. A positive association between cumulative radon gas exposure and lung cancer was demonstrated using both categorical and continuous analyses. The risk estimates obtained in this study indicate that cumulative radon exposure presents an important environmental health hazard.     

The performance of two lichen species as bioaccumulators of trace metals

Epidemiological evidence of lung cancer risk from radon is based mainly on studies of men employed underground in mines where exposures are relatively high in comparison to indoor exposure. Nevertheless, direct evidence of risk from residential radon is desirable. In 1990, a study was started comprising 12,000 inhabitants of an area with elevated radon concentrations. The mean level in the houses was higher than general mean of the country by a factor of five. In the period 1961-1995, a total of 173 lung cancers were observed. Comparing to nationally expected numbers (E), the observed number (O) of cases is elevated (O/E = 1.11), in contrast to generally low figures for cancers other than lung (O/E = 0.85). Lung cancer risk related to cumulative exposures experienced in the past 5-24 or 5-35 years were both significant. In relation to standard radon progeny concentration 100 Bq/m3, the excess relative risk coefficient was 0.103 (95% CI, 0.039-0.168), the value somewhat lower than findings in other indoor studies.     

新疆蒙其古尔铀矿床镭氡平衡系数计算的新方法

镭氡平衡系数是砂岩型铀矿勘查工作中的一项重要参数,及时开展该参数的研究对指导铀矿勘查评价、资源量估算等具有重要的意义。目前,镭氡平衡系数主要由两种方法确定,即分析对比法和物探参数孔观测方法。引入非线性渐近回归方程对物探参数孔观测数据进行曲线拟合,对蒙其古尔铀矿床西山窑组下段镭氡平衡系数进行了计算及研究,并对计算结果进行了对比与评价。两种方法在砂岩型铀矿镭氡平衡系数计算中都非常重要,物探参数孔观测法计算的镭氡平衡系数结果准确性更高。利用非线性渐近回归计算镭氡平衡系数,可以有效地避免由于对观测值最小值与最大值的估算不准而带来的误差,结果更为合理。     

Characterizing the sources,range, and environmental influences of radon 222 and its decay products

Recent results from our group directly assist efforts to identify and control excessive concentrations of radon 222 and its decay products in residential environments. We have demonstrated directly the importance of pressure-induced flow of soil gas for transport of radon from the ground into houses. Analysis of available information from measurements of concentrations in U.S. homes has resulted in a quantitative appreciation of the distribution of indoor levels, including the degree of dependence on geographic location. Experiments on the effectiveness of air cleaning devices for removal of particles and radon decay products indicate the potential and limitations of this approach to control.     

Distribution, speciation, and transport of mercury in stream-sediment, stream-water, and fish collected near abandoned mercury mines in southwestern Alaska, USA

Concentrations of total Hg, Hg (II), and methylmercury were measured in stream-sediment, stream-water, and fish collected downstream from abandoned mercury mines in southwestern Alaska to evaluate environmental effects to surrounding ecosystems. These mines are found in a broad belt covering several tens of thousands of square kilometers, primarily in the Kuskokwim River basin. Mercury ore is dominantly cinnabar (HgS), but elemental mercury (Hg degrees) is present in ore at one mine and near retorts and in streams at several mine sites. Approximately 1400 t of mercury have been produced from the region, which is approximately 99% of all mercury produced from Alaska. These mines are not presently operating because of low prices and low demand for mercury. Stream-sediment samples collected downstream from the mines contain as much as 5500 microg/g Hg. Such high Hg concentrations are related to the abundance of cinnabar, which is highly resistant to physical and chemical weathering, and is visible in streams below mine sites. Although total Hg concentrations in the stream-sediment samples collected near mines are high, Hg speciation data indicate that concentrations of Hg (II) are generally less than 5%, and methylmercury concentrations are less than 1% of the total Hg. Stream waters below the mines are neutral to slightly alkaline (pH 6.8-8.4), which is a result of the insolubility of cinnabar and the lack of acid-generating minerals such as pyrite in the deposits. Unfiltered stream-water samples collected below the mines generally contain 500-2500 ng/l Hg; whereas, corresponding stream-water samples filtered through a 0.45-microm membrane contain less than 50 ng/l Hg. These stream-water results indicate that most of the Hg transported downstream from the mines is as finely-suspended material rather than dissolved Hg. Mercury speciation data show that concentrations of Hg (II) and methylmercury in stream-water samples are typically less than 22 ng/l, and generally less than 5% of the total Hg. Muscle samples of fish collected downstream from mines contain as much as 620 ng/g Hg (wet wt.), of which 90-100% is methylmercury. Although these Hg concentrations are several times higher than that in fish collected from regional baseline sites, the concentration of Hg in fish is below the 1000 ng/g action level for edible fish established by the US Food and Drug Administration (FDA). Salmon contain less than 100 ng/g Hg, which are among the lowest Hg contents observed for fish in the study, and well below the FDA action level.     

Relevance of air conditioning for 222Radon concentration in shops of the Savona Province, Italy

Radon (222Rn) concentration was evaluated in shops of the Savona Province, Italy, between summer 2002 and winter 2002-2003. The main characteristics of each shops were recorded through a questionnaire investigating the ventilation rate and factors related to 222Rn precursors in the soil and the construction materials. The main variables that were related to radon concentration were the following: age of the building, level of the shop above ground, season of the year, wind exposure, active windows, and type of heating system. Shops equipped with individual air heating/conditioning systems exhibited radon concentrations that were three times higher than those of shops heated by centralized furnaces. Our data indicate that the level of pollution in the shops was of medium level, with an expected low impact on the salespersons' health. Only in wintertime, the action level of 200 Bq m(-3) for the confined environment was reached in 10 shops equipped with individual air heating/conditioning systems.     

Indoor radon levels in selected hot spring hotels in Guangdong, China

Guangdong is one of the provinces that have most hot springs in China, and many hotels have been set up near hot springs, with spring water introduced into the bath inside each hotel room for hot spring bathing to attract tourists. In the present study, we measured radon in indoor and outdoor air, as well as in hot spring waters, in four hot spring hotels in Guangdong by using NR-667A (III) continuous radon detector. Radon concentrations ranged 53.4-292.5 Bq L(-1) in the hot spring water and 17.2-190.9 Bq m(-3) in outdoor air. Soil gas intrusion, indoor hot spring water use and inefficient ventilation all contributed to the elevated indoor radon levels in the hotel rooms. From the variation of radon levels in closed unoccupied hotel rooms, soil gas intrusion was found to be a very important source of indoor radon in hotel rooms with floors in contact with soils. When there was spring water bathing in the bathes, average radon levels were 10.9-813% higher in the hotel rooms and 13.8-489% higher in bathes compared to their corresponding average levels when there was no spring water use. Spring water use in the hotel rooms had radon transfer coefficients from 1.6x10(-4) to 5.0x10(-3). Radon in some hotel rooms maintained in concentrations much higher than guideline levels might thus have potential health risks to the hotel workers, and technical and management measures should be taken to lower their exposure of radon through inhalation.     

Radon Risk Mapping using Indoor Monitoring Data - A Case Study of the Lahti Area,Finland

An empirical statistical model is described for the use of indoor radon monitoring data as an indicator of the areal radon risk from soil and bedrock. The percentages of future homes expected to have radon concentrations exceeding the design level of 200 Bq/m³ unless constructed to provide protection against the entry of radon were assessed. The radon prognosis was made for different subareas, soil types and foundation types. This kind of report is used by the health and building authorities. In this study, 2689 indoor radon measurements were made in one of Finland's most radon-prone areas, consisting of eleven municipalities with a total area of 4600 km² and a population of 186,000. Radon concentrations were seasonally adjusted. Data on the location, geology and construction of buildings were determined from maps and questionnaires. The measurements covered different kinds of geological units in the area. The radon risk is highest in the gravel-dominated subarea in an ice-marginal formation and lowest in the northern half of the area in buildings constructed on bedrock. In these two areas, the design level of 200 Bq/m³ would be exceeded in 99% and 39% of new houses with slab-on-grade.     

Large-scale radon hazard evaluation in the Oslofjord region of Norway utilizing indoor radon concentrations, airborne gamma ray spectrometry and geological mapping

We test whether airborne gamma ray spectrometer measurements can be used to estimate levels of radon hazard in the Oslofjord region of Norway. We compile 43,000 line kilometres of gamma ray spectrometer data from 8 airborne surveys covering 10,000 km² and compare them with 6326 indoor radon measurements. We find a clear spatial correlation between areas with elevated concentrations of uranium daughters in the near surface of the ground and regions with high incidence of elevated radon concentrations in dwellings. This correlation permits cautious use of the airborne data in radon hazard evaluation where direct measurements of indoor radon concentrations are few or absent. In radon hazard evaluation there is a natural synergy between the mapping of radon in indoor air, bedrock and drift geology mapping and airborne gamma ray surveying. We produce radon hazard forecast maps for the Oslofjord region based on a spatial union of hazard indicators from all four of these data sources. Indication of elevated radon hazard in any one of the data sets leads to the classification of a region as having an elevated radon hazard potential. This approach is inclusive in nature and we find that the majority of actual radon hazards lie in the assumed elevated risk regions.     

Radon and radon daughter levels in energy efficient housing

radon and radon daughter concentrations have been measured in 33 “energy-efficient” homes in a small subdivision in Kanata, Ontario. Integrated radon measurements were determined over three month periods for a year using solid state nuclear track detectors. Radon and radon daughter grab sample determinations were made during corresponding periods and confirm the distributions of the integrated radon measurements.Annual average individual home radon concentrations show an 8 fold concentration range between homes. This variability in radon concentrations is not reflected in the range of air exchange rates for the homes. A distinct seasonal variation is noted for the median values of the radon and radon daughter concentrations and the equilibrium factor F in the dwellings.     

Modeling ventilation and radon in new Dutch dwellings

Indoor radon concentrations were estimated for various ventilation conditions, the differences being mainly related to the airtightness of the dwelling and the ventilation behavior of its occupants. The estimations were aimed at describing the variation in air change rates and radon concentrations to be expected in the representative newly built Dutch dwellings and identifying the most important parameters determining air change rate and indoor radon concentration. The model estimations were compared with measurements. Most of the air was predicted to enter the model dwelling through leaks in the building shell, independent of the ventilation conditions of the dwelling. Opening the air inlets was shown to be an efficient way to increase infiltration and thus to decrease radon concentration. The effect of increasing the mechanical ventilation rate was considerably less than opening the air inlets. The mechanical ventilation sets the lower limit to the air change rate of the dwelling, and is effective in reducing the radon concentration when natural infiltration is low. Opening inside doors proved to be effective in preventing peak concentrations in poorly ventilated rooms. As the airtightness of newly built dwellings is still being improved, higher radon concentrations are to be expected in the near future and the effect of occupant behavior on indoor radon concentrations is likely to increase. According to the model estimations soil-borne radon played a moderate role, which is in line with measurements.     

Radon risk mapping in southern Belgium: an application of geostatistical and GIS techniques

A data set of long-term radon measurements in approximately 2200 houses in southern Belgium has been collected in an on-going national radon survey. The spatial variation of indoor Rn concentrations is modelled by variograms. A radon distribution map is produced using the log-normal kriging technique. A GIS is used to digitise, process and integrate a variety of data, including geological maps, Rn concentrations associated with house locations and an administrative map, etc. It also allows evaluation of the relationships between various spatial data sets with the goal of producing radon risk maps. Based on geostatistical mapping and spatial analysis, we define three categories of risk areas: high risk, medium risk and low risk area. The correlation between radon concentrations and geological features is proved in this study. High and medium Rn risk zones are dominantly situated in bedrock from the Cambrian to Lower Devonian, although a few medium risk zones are within the Jurassic. It is evident that high-risk zones are related to a strongly folded and fractured context.     

Measuring public knowledge,attitudes, and behaviors related to radon to inform cancer control activities and practices

Radon exposure is the second leading risk factor for lung cancer among smokers and the leading risk factor among non‐smokers. Radon concentrated in lower levels of homes/buildings can be reduced if found, thus lowering lung cancer risk. The objective of this study was to measure radon knowledge in diverse populations, with varying radon‐related laws, to inform radon‐related cancer control practices and activities. A survey was mailed to 3000 homebuyers who purchased single‐family homes; 995 responses (33%) were received. Overall, 86% of respondents heard of radon‐related health issues. Real estate agents (69%) or home inspectors (65%) were the most common sources of information. Respondents were more likely to test their home for radon if they reported previously hearing of radon‐related health issues or understanding of how radon‐related health issues affect the home‐buying process. Respondents in states with notification policies were twice as likely as those without policies to have heard about radon‐related health issues (OR 2.01, 95% CI: 1.27‐3.17). This study provides useful information for cancer control activities including that education is positively associated with home testing for radon. It also suggests partnering with real estate agents to further radon education and testing efforts to reduce radon exposure and lung cancer risk.     

Indoor radon concentrations caused by construction materials in 23 workplaces

The aim of this study was to compare the measured and the calculated concentrations of indoor radon caused by building materials at 23 workplaces. The measured concentrations of radon were clearly higher than the calculated radon concentrations from the building materials, which indicated that the main source of indoor radon was the soil under and around the buildings. The highest means of continuously (933 Bq m(-3)) and integrated (169 Bq m(-3)) measured and calculated (from 70 to 169 Bq m(-3)) concentrations of radon were found in hillside locations. On the other hand, the median (27 and 43 Bq m(-3)) and maximum (626 and 1002 Bq m(-3)) values of calculated indoor radon concentrations exhaled from construction materials were the highest at the ground level places. On average, only 7-19% of the radon seemed to originate from the construction materials.     

Radon and Natural Ventilation in Newer Danish Single-Family Houses

Abstract To investigate the effect of ventilation on indoor radon (²²²Rn), simultaneous measurements of radon concentrations and air change rates were made in 117 Danish naturally ventilated slab-on-grade houses built during the period 1984–1989. Radon measurements (based on CR-39 alpha-track detectors) and air change rate measurements (based on the perfluorocarbon tracer technique; PFT) were in the ranges 12–620 Bq m^?3 and 0.16?0.96 h^?1, respectively. Estimates of radon entry rates on the basis of such time-averaged results are presented and the associated uncertainty is discussed. It was found that differences in radon concentrations from one house to another are primarily caused by differences in radon entry rates whereas differences in air change rates are much less important (accounting for only 80,0% of the house-to-house variation). In spite of the large house-to-house variability of radon entry rates it was demonstrated, however, that natural ventilation does have a significant effect on the indoor radon concentration. Most importantly, it was found that the group of houses with an air change rate above the required level of 0.5 h^?1 on average had an indoor radon concentration that was only 50% (0.5±0.1) of that of the group of houses with air change rates below 0.5 h^?1. The reducing effect of increased natural ventilation on the indoor radon concentration was found to be due mainly to dilution of indoor air. No effect could be seen regarding reduced radon entry rates.     

Theoretical aspects of the design of a passive radon dosemeter

Some mathematical aspects of the development and design of a passive radon dosemeter are considered. In particular, a mathematical model is presented that is concerned with the gaseous diffusion of radon into a confined region bounded by a plastic material of known diffusion coefficient. The relationship between the time-integrated radon concentrations, inside and outside a sealed plastic container are derived. Estimates of the exposure of people to radon can be made using the time integrated radon concentration inside a calibrated container containing a CR-39 etched-track device. As a consequence of the analysis, it is possible to design a passive radon dosemeter that will be accurate, resistant to moisture and whose response will be independent of rapid variations in radon concentration. The possibility of using a container of this type for the measurement of diffusion coefficients is discussed.     

室内氡的危害及控制措施

介绍了氡的性质以及室内氡的主要来源，特别强调了氡对人体的危害，进而介绍了国内室内氡浓度控制的规范与标准，并根据国家标准和它的四大来源，提出了相应的解决办法和防治措施，如不要将居民住宅建造在地质断裂带或工业废渣堆场上，选择符合国家标准的建筑材料来装修等，以保证人的身体健康。     

The influence of meteorological parameters on soil radon levels in permeable glacial sediments

The influence of meteorological parameters on soil radon concentrations in a permeable ice-marginal deposit in Kinsarvik, Norway, was investigated based on continuous measurements of soil radon concentrations, temperature, precipitation, wind speed, wind direction, air pressure and soil moisture content over a period of 10 months. The results show that the soil radon concentrations exhibit distinct seasonal and diurnal variations that predominantly are caused by changes in air temperature. Air flows between areas of different elevation occur in the ice-marginal deposit due to temperature differences between soil air and atmospheric air, and instantaneous changes in air flow direction were recorded when the atmospheric air temperature reached the average annual air temperature. Air pressure was found to be the second most important parameter influencing soil radon concentrations, while no apparent effect of precipitation, wind speed, wind direction or soil moisture was observed. Seasonal variations in indoor and soil radon levels were also investigated in a glaciofluvial deposit located 40 km southwest of Kinsarvik, and the close correlation between the seasonal variation patterns observed in the two areas suggests that the results of the Kinsarvik study also might be applicable to other areas of highly permeable building grounds where differences in terrain elevation exist.