Assessment of exposure to radon decay products in realistic living conditions.

The development of an automated system for activity-weighted size distribution measurements now permits more complete exposure and dose assessment for indoor radon decay products. Exposures characterized by the semi-continuous measurement of activity-weighted size distributions of radon decay products were obtained over four test periods in three normally occupied houses, two of which were occupied by cigarette smokers. These measured activity size distributions were used to calculate exposure-dose conversion coefficients and the annual effective doses. These doses were found to be approximately two-fold higher than the values derived conventionally from the measured radon concentration, on the assumption that indoor exposure to 20 Bq m-3 radon gas concentration corresponds to an annual effective dose 1 mSv y-1. The degree to which aerosol-measurement-based dose estimates were higher than radon-gas-based estimates was found to be influenced if the study house occupant was a cigarette smoker. Reassessment of the measured PAEC-weighted radon progeny particle size distribution in terms of the classical "unattached" and "attached" modes yielded lower estimates of the exposure-effective dose conversion coefficient that were similar to the reference values derived from a recent study by the National Research Council. Thus, by not resolving the measured radon progeny PAEC that is associated with particles intermediate in size between the two classical radon progeny modes, the estimated annual effective doses were also found to be similar to the values derived conventionally from the measured radon gas concentration. It is concluded that the observed presence of 4 to 13% of the radon progeny PAEC in the size-range 1.5 to 15 nm diameter is a dosimetrically significant factor that appears to be commonplace in various home environments.     

Radon and radon daughter measurements in solar buildings

Measurements of radon and radon daughters in 11 buildings in five states, using active or passive solar heating, showed no significant excess in concentrations over the levels measured in buildings with conventional heating systems. Radon levels in two buildings using rock storage in their active solar systems exceeded the U.S. Nuclear Regulatory Commission's limit of 3 pCi/l. for continuous exposure in uncontrolled areas. In the remainder of the buildings, radon concentrations were found to be at levels considered to be normal. It appears that the slightly elevated indoor radon concentrations result from the local geological formations and from the tightening of the buildings rather than as a result of the solar heating technology.     

An improved model for the reconstruction of past radon exposure

If the behavior of long-lived radon progeny was well understood, measurements of these could be used in epidemiological studies to estimate past radon exposure. Field measurements were done in a radon-prone area in the Ardennes (Belgium). The surface activity of several glass sheets was measured using detectors that were fixed on indoor glass surfaces. Simultaneously the indoor radon concentration was measured using diffusion chambers. By using Monte Carlo techniques, it could be proven that there is a discrepancy between this data set and the room model calculations, which are normally used to correlate surface activity and past radon exposure. To solve this, a modification of the model is proposed.     

Population attributable fraction for lung cancer due to residential radon in Switzerland and Germany

Studies on miners as well as epidemiological studies in the general population show an increased lung cancer risk after exposure to radon and its progeny. The European pooled analysis of indoor radon studies estimates an excess relative risk of 8% (16% after correction for measurement uncertainties) per 100 Bq m(-3) indoor radon concentration. Here, we determine the population attributable fraction (PAF) for lung cancer due to residential radon based on this risk estimate for Switzerland and Germany. Based on regionally stratified radon data, the PAF was calculated following the World Health Organization concept of global burden of disease, compared to a realistic baseline radon concentration equal to the outdoor concentration. Lifetable approaches were used taking smoking and sex into account. Measurement error corrections were applied to both risk estimates and the radon distribution. In Switzerland, the average indoor radon concentration is 78 Bq m(-3), resulting in a PAF of 8.3%. Therefore, 169 male lung cancer deaths and 62 deaths in women can be attributed to residential radon per year. For Germany, the average indoor radon concentration is 49 Bq m(-3), corresponding to a PAF of 5.0% (1,422 male and 474 female deaths annually). In both countries, a large regional variation in the PAF was observed due to regional differences in radon concentrations and population structure. Both calculations show a strong dependency on the risk model used. Risk models based on miner studies result in higher PAF estimates than risk models based on indoor radon studies due to different assumptions regarding exposures received more than 35 years ago. The use of a non-zero baseline radon concentration also contributes to the lower PAF estimates reported here. Although the estimates of the population attributable fraction of residential radon presented here are lower than previously reported estimates, the risk is still one of the most widespread environmental hazards. Radon monitoring and radon reduction programs are therefore important issues for environmental public health management.     

Indoor radon progeny exposure in the Florida phosphate mining region: a review

This paper reviews the data generated in studies of land radioactivity and indoor airborne radon progeny associated with mined and reclaimed phosphate lands in Florida. Highest indoor radon progeny levels are associated with the slab-on-grade type of construction. Concentrations exceeding 0.03 WL are associated with overburden soils, deposits and fill, while concentrations up to about 0.03 WL are associated with tailings. The lower limit for distinguishing increases above non-enhanced natural concentrations is on the order of 0.01-0.02 WL. Results of this study show that about 25% of the land produced by present methods of mining and reclamation practices would require restrictions on the type of construction or would require special construction methods. It is projected that with modification of mining and tailings disposal practices, virtually all of the land produced by mining and reclamation would be satisfactory for unrestricted construction use.     

Building-specific factors affecting indoor radon concentration variations in different regions in Bulgaria

The study was conducted to assess the spatiality of the building factors’ effect on air quality through evaluation of indoor radon concentration in areas with different geology and geographical position. For that matter, a survey of indoor radon concentration was carried out in 174 kindergartens of three Bulgarian cities. The time-integrated measurements were performed in 777 ground floor rooms using alpha tract detectors, exposed for 3 months in cold period of 2014. The results of indoor radon concentrations vary from 20 to 1117 Bq/m³. The differences in the mean radon concentrations measured in the different cities were related to geology. The effect of building-specific factors: elevator, basement, mechanical ventilation, type of windows, number of floors, building renovation, building materials, type of room, type of heating, construction period, and availability of foundation on radon concentration variations was examined applying univariate and multivariate analysis. Univariate analysis showed that the effects of building-specific factors on radon variation are different in different cities. The influence of building factors on radon concentration variations was more dominant in inland cities in comparison to the city situated on the sea coast. The multivariate analysis, which was applied to evaluate the impact of building factors simultaneously, confirmed this influence too.     

The concept of equivalent radon concentration for practical consideration of indoor exposure to thoron

To consider the total exposure to indoor radon and thoron, a concept of equivalent radon concentration for thoron is introduced, defined as the radon concentration that delivers the same annual effective dose as that resulting from the thoron concentration. The total indoor exposure to radon and thoron is then the sum of the radon concentration and the equivalent radon concentration for thoron. The total exposure should be compared to the radon guideline value, and if it exceeds the guideline value, appropriate remedial action is required. With this concept, a separate guideline for indoor thoron exposure is not necessary. For homes already tested for radon with radon detectors, Health Canada's recommendation of a 3-month radon test performed during the fall/winter heating season not only ensures a conservative estimate of the annual average radon concentration but also covers well any potentially missing contribution from thoron exposure. In addition, because the thoron concentration is much lower than the radon concentration in most homes in Canada, there is no real need to re-test homes for thoron.     

Investigation of the air pressure characteristics influencing the variability of radon gas and radon progeny in domestic vernacular buildings.

Analysis of time-series data sets collected in vernacular buildings linked with radium source bedrock has identified a number of internal and external pressure characteristics linking meteorological parameters with the variability of radon gas and its progeny. The buildings' cellars built into the bedrock associated with the radium source have relatively high levels of radon concentration. These cellars have essentially stable microclimatic conditions, unlike the ground and upper levels of the buildings. Comparative radon concentration data collected from various comparable buildings suggest the need to distinguish between short and longer-term influences on radon concentrations. Water vapor pressure is inferred to be a principal determinant of the short-term variability of radon gas concentrations. Barometric pressure is suggested as determining the trend or general longer-term level of radon. Both of these pressure components are related to temperature. Wind speed appears to have a dual influence on radon variability: directly, through wind pressure relative to the ground and building structure particularly associated with low-pressure weather regimes; and indirectly, through changes to the water vapor pressure component.     

Models for retrospective quantification of indoor radon exposure in case-control studies

In epidemiologic studies on lung cancer risk due to indoor radon the quantification of individual radon exposure over a long time period is one of the main issues. Therefore, radon measurements in one or more dwellings, which in total have been inhabited by the participants for a sufficient time-period, are necessary as well as consideration of changes of building characteristics and ventilation habits, which influence radon concentration. Given data on 1-y alpha-track measurements and personal information from 6,000 participants of case-control studies in West and East Germany, an improved method is developed to assess individual radon exposure histories. Times spent in different rooms of the dwelling, which are known from a personal questionnaire, are taken into account. The time spent outside the house (average fraction 45%) varies substantially among the participants. Therefore, assuming a substantially lower radon exposure outside the dwelling, the residence time constitutes an important aspect of total radon exposure. By means of an analysis of variance, important determinants of indoor radon are identified, namely constant conditions such as type of house (one family house or multiple dwelling), type of construction (half-timbered, massive construction, lightweight construction), year of construction, floor and type of basement, and changeable conditions such as heating system, window insulation, and airing habits. A correction of measurements in former dwellings by factors derived from the analysis is applied if current living conditions differ from those of the participants at the time when they were living in the particular dwellings. In rare cases the adjustment for changes leads to a correction of the measurements with a factor of about 1.4, but a reduction of 5% on average only. Exposure assessment can be improved by considering time at home and changes of building and ventilation conditions that affect radon concentration. The major concern that changes in ventilation habits and building conditions lead to substantial errors in exposure (and therefore risk) assessment cannot be confirmed in the data analyzed.     

Study of indoor radon levels in high-rise air-conditioned office buildings

A series of measurements were conducted to study the indoor radon pollution in air-conditioned high-rise office buildings. Continuous monitoring of indoor radon levels in nine air-conditioned premises located in six office buildings in Hong Kong was conducted from August 1996 to February 1998. Each of the tests lasted for at least 48 hours. The measurement covered both day time monitoring while the air-conditioning was on and night time monitoring while the air-conditioning was off. The indoor radon level followed inversely the operation pattern of the mechanical ventilation systems in the buildings. During office hours when the mechanical ventilation was on, the indoor radon level decayed and after the mechanical ventilation was off during non-office hours, the radon level increased. The average indoor radon level during office hours on the nine premises varied from 87 Bq/m3 to 296 Bq/m3, and the indoor averaged radon levels over both day time and night time periods without mechanical ventilation were about 25 percent higher. The air infiltration rate and the radon emission characteristics from the building materials were estimated from the radon build-up curves which were observed after the mechanical ventilation was off. The radon decay curve observed after the mechanical ventilation system was turned on was used to calculate the total fresh air intake rate. Average radon emanation rates of the building materials in the six buildings varied from 0.0019 to 0.0033 Bq/m2s. It has been found that building infiltration rate accounted for about 10-30 percent of the total building ventilation rate in the buildings depending on building tightness.     

Indoor radon and well water radon in Virginia and Maryland

The domestic use of radioactive water has long been a cause for concern, but only a few studies have examined prolonged exposure to radionuclide concentrations found in natural settings. This paper reports on the indoor radon concentrations from 1,500 homes in northern Virginia and southern Maryland and well water radon from 700 homes in the same area. Indoor radon concentrations are almost all between 1 and about 40 pCi/L. The winter season shows the highest values with about 40% of the homes over the US EPA action level of 4.0 pCi/L. The summer season shows the lowest values with about 25% of the homes over this level. This seasonal variation is related to home ventilation. Waterborne radon in homes with private well ranges from about 100 pCi/L to about 8,000 pCi/L. In small homes, indoor radon can be significantly increased by outgassing of the home water supply, even at water radon levels of less than 10,000 pCi/L.     

Dosimetry of radon progeny deposited on skin in air and thermal water

It is held that the skin dose from radon progeny is not negligibly small and that introducing cancer is a possible consequence under normal circumstances as there are a number of uncertainties in terms of related parameters such as activity concentrations in air and water, target cells in skin, skin covering materials, and deposition velocities. An interesting proposal has emerged in that skin exposure to natural radon-rich thermal water as part of balneotherapy can produce an immune response to induce beneficial health effects. The goal of this study was to obtain generic dose coefficients with a focus on the radon progeny deposited on the skin in air or water in relation to risk or treatment assessments. We thus first estimated the skin deposition velocities of radon progeny in air and thermal water based on data from the latest human studies. Skin dosimetry was then performed under different assumptions regarding alpha-emitting source position and target cell (i.e. basal cells or Langerhans cells). Furthermore, the impact of the radon progeny deposition on effective doses from all exposure pathways relating to ‘radon exposure’ was assessed using various possible scenarios. It was found that in both exposure media, effective doses from radon progeny inhalation are one to four orders of magnitude higher than those from the other pathways. In addition, absorbed doses on the skin can be the highest among all pathways when the radon activity concentrations in water are two or more orders of magnitude higher than those in air.     

十堰市城区居民室内氡浓度调查结果与分析

目的 对十堰市城区居民室内氡浓度进行监测,分析居民室内氡浓度水平及影响因素。方法 从2019年4月到7月,采用RSKS标准型探测器对十堰市城区共计125户居民室内氡浓度进行测量并分析。结果 2019年所监测的十堰城区居民室内氡浓度结果呈偏态分布,范围为13.8～145 Bq/m³,M(P₂₅,P₇₅)为38.3(29.0,62.0) Bq/m³,居民因吸入氡及其子体产生的年均有效剂量估算值为0.52～5.50 mSv,M(P₂₅,P₇₅)为1.45(1.10,2.36) mSv,与相关文献一致;不同建筑结构(H=14.10,P<0.001)、楼层(H=24.41,P<0.001)和地区(H=8.963,P<0.05)均是居民室内氡浓度水平的影响因素,且差异均有统计学意义。结论 十堰市城区居民室内氡浓度小于国家标准限值,但在日常生活中还是需要注意采取合适的方法,尽量降低家中氡浓度。     

210Pb in home dust as a possible marker for radon exposure in indoor air

Exposure to indoor radon is of great concern because it is an environmental hazard for developing lung cancer. 210Pb, a radon decay product, was measured in home dust samples from the city of Ottawa, Canada. The 210Pb level in dust ranged from 33 to 352 Bq kg(-1), with the geometric mean and median values of 105 and 110 Bq kg(-1), respectively. Despite the complexity of the formation of 210Pb in the indoor environment, an encouraging correlation between 210Pb concentrations in home dust and radon levels in indoor air was observed when the measurement data were grouped according to four geographic regions of the city. This observation could lead to the development of 210Pb in home dust as a potential marker for indoor radon exposure.     

Activity size distribution of radon progeny in indoor air: comparison of model to data.

The activity size distributions of radon progeny in indoor air are considered. A general theoretical model is presented and then applied to this experiment where experimental data was obtained in a very large and nearly airtight laboratory for two cases: low particle concentration (Case 1) and high particle concentration (Case 2). The balance equations of aerosol particles, radon, and radon progeny in indoor air are solved numerically. The effects of particle coagulation are noticeable for u = 0.005 ms-1, (u. equals friction velocity) but negligible for u = 0.015 ms-1 as long as we adopt a certain theoretical model of wall deposition. Numerical results agreed rather well with this experimental data. Furthermore, an example calculation was done in the case of a usual living space with a high air-exchange rate.     

Radon mitigation survey among New York State residents living in high radon homes.

Residential exposure to radon has been considered an important environmental risk factor for lung cancer. Since 1986, U.S. EPA has recommended that all dwellings below the third floor be tested for the presence of radon and be mitigated to reduce indoor radon in homes with levels exceeding 148 Bq m(-3). In order to evaluate the effectiveness of New York State Department of Health's efforts to increase public awareness about radon risk and to promote radon testing and mitigation in compliance with EPA's guideline, a statewide radon mitigation survey was conducted between September 1995 and January 1996 among New York State residents whose homes had radon levels equal to or greater than 148 Bq m(-3) on the first floor (or above) living areas. The survey found that about 60% of 1,113 participants had taken actions for radon mitigation. The percentage of respondents who took actions to reduce radon levels in their homes increased with increasing education level as well as household income level. The method of installing a powered system to provide more ventilation was a more effective mitigation method than opening widows/doors or sealing cracks/openings in the basement. Mitigation performed by contractors was more effective in reducing radon levels than mitigation performed by residents. The reasons for performing radon mitigation given by the majority of respondents were those strongly related to radon health risk. High home radon level was an important motivational factor to stimulate radon mitigation. On the other hand, the cost of radon mitigation was a major barrier in decision making for performing radon mitigation and for selecting mitigation measures. Thus, public educational campaigns that focus on increasing awareness and knowledge about radon health risks and development of less expensive radon mitigation methods may help in promoting radon mitigation.     

Exposure to atmospheric radon.

We measured radon (222Rn) concentrations in Iowa and Minnesota and found that unusually high annual average radon concentrations occur outdoors in portions of central North America. In some areas, outdoor concentrations exceed the national average indoor radon concentration. The general spatial patterns of outdoor radon and indoor radon are similar to the spatial distribution of radon progeny in the soil. Outdoor radon exposure in this region can be a substantial fraction of an individual's total radon exposure and is highly variable across the population. Estimated lifetime effective dose equivalents for the women participants in a radon-related lung cancer study varied by a factor of two at the median dose, 8 mSv, and ranged up to 60 mSv (6 rem). Failure to include these doses can reduce the statistical power of epidemiologic studies that examine the lung cancer risk associated with residential radon exposure.     

Simulation of the radon and radon progeny detection by silicon photodiodes

The use of silicon photodiodes for field radon measurements requires the utilization of measuring cells for protection against environmental electromagnetic fields. It is very important to study and optimize the impact of geometry conditions (dimensions of the measuring cell) on the photodiode detection efficiency that can be reduced more than 10-30 times. Two models (for volume-distributed nuclides around the detector and for radon progeny deposited on the diode surface radon progeny) were applied for simulation of the photodiode detection in measuring cells of different sizes. Their use allows an optimal choice of the most appropriate cell regarding the measurement conditions. Thus, for soil gas measurements cells we use a cell of 3.6 cm in diameter by 20 cm in height; for determination of the radon exhalation rate we use a cell of 16 cm in diameter by 14 cm in height; and for measurements in dwellings and large spaces we use cells larger than 20 cm and lower than 4 cm.     

Nationwide survey of radon levels in Korea

A nationwide radon survey was conducted to provide data on the annual average indoor radon concentration in Korean homes. This survey also provided data on the variation of radon concentration with season, house type, and building age. The arithmetic mean (AM) of annual radon concentration in Korean homes was 53.4 +/- 57.5 Bq m(-3). The indoor radon concentration showed a lognormal distribution with a geometric mean (GM) and its standard deviation (GSD) of 43.3 +/- 1.8 Bq m(-3). The radon concentrations in the traditional Korean-style houses were about two times higher than those in apartments and row houses. The average annual outdoor radon concentration was 23.3 Bq m(-3). The average annual effective dose to the general public from radon was 1.63 mSv y(-1).     

湛江市部分住房室内外空气中氡浓度测定

采用活性炭吸附闪烁法测定了湛江市部分住房室内、外空气中的平衡当量氡浓度。结果表明 ,住房室内、外空气中平衡当量氡浓度平均值分别为 2 5 2 7Bq/m3 和 14 6 8Bq/m3 ,室内空气中平衡当量氡浓度显著高于室外 (P <0 0 1) ;不同装饰材料的住房室内空气中平衡当量氡浓度各有差异 ,其中以花岗岩为装饰材料的住房室内平衡当量氡浓度 (31 18Bq/m3 )为最高 ,水泥地板住房 (14 71Bq/m3 )最低