High Radon Levels Research Articles

Effect of soil parameters on radon entry into a building by means of the transrad numerical model.

High indoor radon concentration means an increased risk of developing lung cancer. When high radon levels are present in a dwelling, the major source is normally the soil. Therefore, it is useful to know the radon concentration field in the soil underneath a building. A steady-state two-dimensional radon transport model has been used to calculate the effect of a reference building on the soil radon concentration, and the influence of soil parameters on radon entry through a single crack in the basement. Both advective and diffusive flows are considered. Away from the building, the well-known undisturbed soil radon concentration profile has been obtained, while under the house the radon level is increased. A variability analysis around the reference site has shown that the most relevant soil parameters on the radon flux at the top of the crack are, in this case, effective diffusion coefficient, soil gas-permeability and deep soil radon concentration.

Groundwater radon measurements in the Mt. Etna area

Radon levels were measured in 119 groundwater samples collected throughout the active volcanic area of Mt. Etna by means of a portable Lucas-type scintillation chamber. The measured activity values range from 1.8 to 52.7 Bq l −1. About 40% of the samples exceed the maximum contaminant level of 11 Bq l −1 proposed by the USEPA in 1991. The highest radon levels are measured in the eastern sector of the volcano, which is the seismically most active zone of the volcano. On the contrary the south-western sector, which is both seismically active and a site of intense magmatic degassing, display lower radon levels. This is probably due to the formation of a free gas phase (oversaturation of CO 2) that strips the radon from the water. Comparison of the data gathered at Mt. Etna with those of other areas indicates that 222Rn activity in groundwater is positively correlated with both the content of parent elements in the aquifer rocks and the temperature of the geothermal systems that interacts with the sampled aquifers.

Relationship between radon concentrations in indoor air and in soil gas

In the Ljubljana region, 53 schools were selected for measurements of radon concentrations in soil gas close to a school building, and indoor radon concentrations in one of the ground-floor classrooms of each building. The aim was to establish a relationship between radon concentrations in indoor air and in soil gas from the ground on which the building is situated. Soil gas radon concentrations between 2 and 14 kBqm–3 were found. Indoor radon concentrations ranged from 20 to 1,440 Bqm–3, with seven values exceeding 200 Bqm–3. It is concluded that good quality of the construction elements ensure low indoor radon concentration, regardless of high soil gas radon level.

Identification of sources of high radon levels in Slovenian schools.

The sources of radon were investigated in twenty selected schools with high room levels of radiation. A combination of radon measuring techniques was applied: etched track and electret detectors to obtain average indoor air radon concentration. devices to record radon concentration continuously and thus characterise its diurnal variation, and alpha scintillation cells to analyse air from potential sources of radon entry. In some cases, a single strong source was identified (e.g. sinks, sub-floor channels), while in others the poor quality of the basic concrete slab was responsible for high indoor radon concentrations. The combination of etched track and electret detectors and alpha scintillation cells was essential for locating these sources.

Residential radon and lung cancer risk in a high-exposure area of Gansu Province, China.

In the general population, evaluation of lung cancer risk from radon in houses is hampered by low levels of exposure and by dosimetric uncertainties due to residential mobility. To address these limitations, the authors conducted a case-control study in a predominantly rural area of China with low mobility and high radon levels. Included were all lung cancer cases diagnosed between January 1994 and April 1998, aged 30-75 years, and residing in two prefectures. Randomly selected, population-based controls were matched on age, sex, and prefecture. Radon detectors were placed in all houses occupied for 2 or more years during the 5-30 years prior to enrollment. Measurements covered 77% of the possible exposure time. Mean radon concentrations were 230.4 Bq/m(3) for cases (n = 768) and 222.2 Bq/m(3) for controls (n = 1,659). Lung cancer risk increased with increasing radon level (p < 0.001). When a linear model was used, the excess odds ratios at 100 Bq/m(3) were 0.19 (95% confidence interval: 0.05, 0.47) for all subjects and 0.31 (95% confidence interval: 0.10, 0.81) for subjects for whom coverage of the exposure interval was 100%. Adjusting for exposure uncertainties increased estimates by 50%. Results support increased lung cancer risks with indoor radon exposures that may equal or exceed extrapolations based on miner data.

Radon exposure in Ireland

Background: A survey of radon in domestic dwellings in Ireland has recently been completed by the Radiological Protection Institute of Ireland (RPII). This survey was carried out to identify areas of the country most at risk from high indoor radon levels. Methods: The survey was geographically based using the 10-km grid squares of the National Grid as the unit area. Indoor radon measurements were carried out for 12 months using CR-39 detectors in houses selected at random throughout the country. The results were used to predict the percentage of houses in each grid square with radon levels in excess of 200 Bq/m 3 (the reference level for houses). Results: Radon measurements were carried out in 11,319 houses throughout the country. Radon levels varied from 10 to 1924 Bq/m 3 with an average indoor radon concentration of 89 Bq/m 3. Using the GeoDirectory database, it can be estimated that approximately 91,000 houses throughout the country have indoor levels in excess of 200 Bq/m 3. Conclusions: The results of the survey will be used to target new surveys in order to identify the 65% of high radon houses located in high-radon areas. To address the issue of radon in new houses, the Building Regulations have been amended to require the incorporation of radon preventative measures during construction.

Comparative studies of health hazard from radon (Rn-222) in two selected lithologic formations in the Suwałki region (in Poland)

The aim of this work was to make a comparison of indoor radon concentrations in dwellings and in soil air in the area of two geological formations in the Suwałki region (Poland). The mean arithmetic airborne concentration was found to be the highest (301 Bq m −3) in the basements of buildings in the gravel and sand areas, whereas in the boulder clay areas it reached 587 Bq m −3. Out of 54 measurements of radon concentrations performed at the ground floor, in eight cases concentrations were found to exceed 200 Bq m −3—permissible radon level in new-built houses in Poland and in three cases these values were even higher than 400 Bq m −3. The highest radon levels were noted in houses with earthen basement floors and with direct entrance from the basement to rooms or kitchens. The mean arithmetic radon concentration in the soil air in the sandy and gravel formations was 39.7 kBq m −3 and in clay formation it was 26.5 kBq m −3. Higher radon levels were also found in the water obtained from household wells reaching 8367 Bq m −3 as compared with tap water (2690 Bq m −3). The mean indoor concentration for the whole area under study was found to be 169.4 Bq m −3, which is higher than the mean value for Poland (49.1 Bq m −3) by a factor of 3.5.

Search for radon sources in buildings — kindergartens

In ten high radon level kindergartens, radon sources were sought by applying a combination of several radon measuring techniques: etched track detectors to obtain average indoor air radon concentration, continuous devices to record radon concentration and see its diurnal variation, and alpha scintillation cells to determine radon concentration in the air entering a room from cracks, holes and sinks in the floor and from under-floor channels. In three cases, a strong local radon source was identified while, in the others, the bad quality of the basic concrete slab was responsible for the high indoor radon concentration.

Radon entry, migration and reduction in houses with cellars

Soil radon entry to a house and indoor concentration level are affected by many factors, such as the infiltration characteristics of the house, air tightness of the substructure of the house, air permeability of the soil, radon content in the soil and many others. Amongst them, the structure of the house, particularly its substructure is certainly one of the most crucial factors. It determines radon entry routes and indoor radon distribution, and consequently, affects the effectiveness of radon control measures applied in the house. The paper focuses on houses with cellars, a type of dwelling in Derbyshire, North England where high indoor radon levels have been found in over 20% homes. Based on the results of an initial study, a conceptual house was constructed bearing the major features of such types of houses. A modelling strategy was established which integrated two previously developed computer models. Such integration made it possible to simulate a complete course of radon migration, from its generation by soil grains, transport with soil gas and decay in soil matrix to its entry through the substructure of the house and moving from one room to another, and finally its dispersion into atmosphere. Using this modelling strategy, a parametric study was carried out to examine the effects of some crucial aspects on the indoor radon level throughout the house, including the ambient temperature, the wind speed and direction and most importantly the cellar ventilation, a simple remedial solution to radon reduction for this type of house.

Indoor radon/thoron levels and inhalation doses to some populations in Himachal Pradesh, India.

It is well established that some areas of Himachal Pradesh (H.P.) state of India situated in the environs of the Himalayan mountains are relatively rich in uranium-bearing minerals. Some earlier studies by our group have indicated high levels of radon (>200 Bq m(-3)) in the dwellings. It is in this context that an indoor radon/thoron survey has been carried out in selected villages of four districts in the state of H.P. This survey has been conducted as a part of a national, coordinated project using twin chamber dosemeter cups designed by the Environmental Assessment Division (EAD), Department of Atomic Energy, Govt. of India. The track-etch technique is used for calibration of plastic detector LR-115 type-II which are employed for recording alpha tracks due to radon/thoron and their daughters. Year long radon/thoron data have been collected for seasonal correlations of indoor radon/thoron in the dwellings. The indoor radon levels have been found to vary from a minimum value of 17.4 Bq m(-3) to a maximum value of 140.3 Bq m(-3). The indoor thoron levels vary from a minimum value of 5.2 Bq m(-3) to a maximum value of 131.9 Bq m(-3). The year average dose rate for the local population varies from 0.03 microSv h(-1) to 0.83 microSv h(-1). The annual exposure dose to inhabitants in all the dwellings lies below the upper limit of 10 mSv given in ICRP-65.

Airborne radon and its progeny levels in the coal mines ofGodavarikhani, Andhra Pradesh, India*

In India, out of about 0.7 million miners, nearly 0.5 million persons aredirectly engaged in coal operations. Radon and its progeny levels have beenquantified in the coal-mining environment of Godavarikhani, Andhra Pradesh,India using solid-state nuclear track detectors. Seasonal and mine depthvariations in radon levels have been recorded resulting in theidentification of locations with a high radon level as areas with no miningactivity, active mining operational zones and return air ventilation paths.All these radon levels were below the permissible levels. The averageconcentrations of radon and its progeny levels were found to be 144±61 Bq m-3 and 20±11 mWL (working level) respectively in thetwo-incline mine, and these values for the five-incline mine are recordedas 315±71 Bq m-3 and 30±9 mWL respectively.

Study on a new method for reducing radon level in indoor air

The aim of this study is to develop a new technique for reducing high radon level in indoor air by method of membrane permeation using a hollow fiber module. The experiment has been carried out for MERASILOX-S module of fine hollow fibers of silicon rubber that has high permeability constant and MHF hollow fiber module made of thin segment polyurethane membrane. The radon permeability constants of hollow fiber membranes have been estimated from the decrease rate of radon concentration in a radon permeation system. The apparent permeability constant depends on the flow rate through the outside and the inside of hollow fibers. The apparent permeability constants of MERASILOX-S and MHF module membranes were 3.9×10 -9 m 2. s -1 and 1.1×10 -9 m 2. s -1 at the flow rate above 5.0 L . min -1 . However, the permeation velocity of MHF module is grater than that of MERASILOX-S module. The radon concentration in a 50 m 3 room of concrete building could be reduced to about 1/10 by using a MHF module with membrane area of 18 m 2 . The use of pressure different between the inside and the outside of hollow fibers might be applied to reduce the environmental radon concentration.

Chromosome aberrations study of pupils in high radon level elementary school.

The ICRP Publication 65 recommends 200-600 Bq x m(-3) as the indoor radon action level for the general public. In Slovenia, a value of 400 Bq x m(-3) has been proposed but not yet approved. In a nation-wide radon project financed by the Health Inspectorate of Slovenia, it was discovered that the elementary school named "S3" belongs to a group of schools with elevated winter indoor radon concentrations up to 7,000 Bq x m(-3). Opening windows and doors during classes substantially decreased radon concentrations, but very seldom below 1,000 Bq x m(-3). Yearly effective doses for pupils, estimated according to ICRP 65, ranged from 7 to 11 mSv. Because the pupils have been subjected to the elevated radon concentrations, special preventive health checks have been performed. The examination protocol included mutagenetic tests, one for structural chromosomal aberrations and the other a micronucleus test. Altogether 85 pupils (37 girls and 48 boys) from the first four grades between the ages of 9 and 12 y were examined. An increase in cytogenetic damage was found for these pupils, compared to the control group, composed of pupils of the same age from another area with indoor radon concentrations in their school of below 400 Bq x m(-3). The incidence of structural chromosomal aberrations reached 2.0% (0.5-4) and micronucleus test was 6.52 per 500 cells with a maximum of 15 in some cases. In the control group structural chromosomal aberrations varied from 0.5 to 2.5%, while the maximum incidence of micronucleus was 9 micronucleus per 500 CB cells. The results obtained are preliminary and suggest a need to expand the study. A long-term radon survey, at least over a year, of the homes and wider residential environment of the pupils would be necessary to assess the correlation between radon exposure and both structural chromosomal aberrations and micronucleus findings.

Black shales are insignificant sources of residential radon in the Kansas City area

Abstract Results of 128 radon screening tests performed by homeowners living in Jackson County, Missouri, and Johnson County, Kansas, are compared to four geologic variables. Slightly higher radon levels are associated with gray shale bedrock and loess-derived soil, but no statistically-significant relationships are found between radon screening levels and bedrock types, soil parent or soil permeability. Previous emphasis on black shales as a principal source of radon precursors in the Kansas City area is unwarranted. The single significant relationship found in this study is that homes built on slopes do possess statistically-higher radon screening levels than those built in upland areas.

Radon ( [formula omitted]) level variations on a regional scale: influence of the basement trace element (U, Th) geochemistry on radon exhalation rates

The approach proposed in this study provides insight into the influence of the basement geochemistry on the spatial distribution of radon ( 222 Rn ) levels both at the soil/atmosphere interface and in the atmosphere. We combine different types of in situ radon measurements and a geochemical classification of the lithologies, based on 1/50 000 geological maps, and on their trace element (U, Th) contents. The advantages of this approach are validated by a survey of a stable basement area of Hercynian age, located in South Brittany (western France) and characterized by metamorphic rocks and granitoids displaying a wide range of uranium contents. The radon source-term of the lithologies, their uranium content, is most likely to be the primary parameter which controls the radon concentrations in the outdoor environment. Indeed, the highest radon levels (⩾100 Bq m −3 in the atmosphere, ⩾100 mBq m −2 s −1 at the surface of the soil) are mostly observed on lithologies whose mean uranium content can exceed 8 ppm and which correspond to peraluminous leucogranites or metagranitoids derived from uraniferous granitoids.

Systematic indoor radon and gamma-ray measurements in Slovenian schools.

During the winter months of 1992/93 and 1993/94, instantaneous indoor radon concentrations and gamma dose rates were measured in 890 schools in Slovenia attended in total by about 280,000 pupils. Under "closed conditions," the room to be surveyed was closed for more than 12 h prior to sampling, the air was sampled into alpha scintillation cells with a volume of 700 cm3, and alpha activity was measured. An arithmetic mean of 168 Bq m(-3) and a geometric mean of 82 Bq m(-3) were obtained. In 67% of schools, indoor radon concentrations were below 100 Bq m(-3), and in 8.7% (77 schools with about 16,000 pupils) they exceeded 400 Bq m(-3), which is the proposed Slovene action level. In the majority of cases, radon concentrations were high due to the geological characteristics of the ground. Approximately 70% of schools with high radon levels were found in the Karst region. Gamma dose rates were measured using a portable scintillation counter. An arithmetic mean of 102 nGy h(-1) and a geometric mean of 95 nGy h(-1) were obtained. No extraordinarily high values were recorded.

The concentrations and distributions of U and Th in Paleozoic aquifers surrounding the Llano Uplift area, central Texas, U.S.A.: application to the sources of Ra and Rn in groundwater

Interactions between groundwater and aquifer rock can result in anomalously high levels of radium (Ra) and radon (Rn) in groundwaters. An understanding of aquifer mineralogy and determining the sources of natural radionuclides are, therefore, essential to design possible means for improving groundwater quality. The Cambrian Hickory Sandstones and Cap Mountain Limestones constitute important aquifers in the area surrounding the Llano Uplift in central Texas. Groundwaters produced from these aquifers, however, have anomalous concentrations of Ra and Rn, much greater than the maximum contaminant levels (MCL) suggested by the USEPA. To determine the sources of Ra and Rn, the abundance, distribution, and nature of occurrence of U and Th, parent radionuclides of Ra and Rn, were examined in cored aquifer rock samples.

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.

Influence of Local Geology on the Concentration of Indoor Radon in Maryland

Approximately 58,000 indoor radon measurements are available for homes in Maryland. A comparative study between compilations of activated-charcoal and alpha-track measurements of indoor radon in zip-code-size geographic areas indi cated that both of these methods are useful and are equally able to estimate regional indoor radon. Indoor radon measurements compiled according to zip code areas can be used to create state-size radon hazard maps. In Maryland the area with the highest indoor radon (mostly composed of zip code areas that average over 8 pCi/L) is the western half of the Piedmont Province and the eastern side of the Coastal Plain Province. The eastern half of the Piedmont and the eastern half of the Valley and Ridge mostly have intermediate and high indoor radon levels (4-8 and > 8 pCi/L). The Blue Ridge, western side of the Valley and Ridge, and Plateau Province each has relatively few zip code areas, but the data suggest a range from low to high indoor radon levels. The western side of the Coastal Plain has the lowest indoor radon (most of the zip code areas average less than 4 pCi/L).

Experience from using plastic film in radon measurement

Plastic film is a useful detector of radon gas. The method of detection of the gas is used for several decades to measure radon concentrations both indoors and in soil. Experiences from radon measurements in Sweden indoors, in soil and in water using the plastic film Kodak LR 115-II are discussed in this report. Some examples are given from various projects. One example is taken from a large scale mapping of indoor radon levels in houses, where the building material is the main source of radon. In anotther example the measurements from a large scale soil radon mapping are discussed. The use of the plastic film for measurements of radon levels in water is also discussed. All the investigations are made in order to give the authorities concerned information of the radon situation and to study the connection between high indoor radon levels and various types of cancers.