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PubMed1993

Radon exposure and leukaemia in adulthood.

Positive associations between leukaemia and radon concentrations have been observed in England, Scotland and Wales, and Canada. Results of a similar study for the populations of 41 French administrative areas ('départements') are reported for 1984-1986. The average indoor radon and gamma ray concentrations per 'département' range from 12 to 147 Bq.m-3 and from 28 to 142 nG.h-1, respectively. Acute lymphoid leukaemia mortality rate is similar to the national level, whereas an excess of acute myeloid leukaemia deaths is observed. According to Poisson regression models and modified tests for partial correlation, acute myeloid leukaemia mortality is significantly and positively related to indoor radon concentration whether or not adjustment is made for indoor gamma ray dose, socioeconomic status and linear gradient. This result reinforces the evidence that indoor exposure to high levels of radon is a leukaemic environmental hazard.

Acute Disease↗
PubMed2002

Uncertainty analysis of the weighted equivalent lung dose per unit exposure to radon progeny in the home.

A parameter uncertainty analysis has been performed to derive the probability distribution of the weighted equivalent dose to lung for an adult (w(lung) H(lung)) per unit exposure to radon progeny in the home. The analysis was performed using the ICRP Publication 66 human respiratory tract model (HRTM) with tissue weighting factor for the lung, w(lung) = 0.12 and the radiation weighting factor for alpha particles, wR = 20. It is assumed that the HRTM is a realistic representation of the physical and biological processes, and that the parameter values are uncertain. The parameter probability distributions used in the analysis were based on a combination of experimental results and expert judgement from several prominent European scientists. The assignment of the probability distributions describing the uncertainty in the values of the assigned fractions (ABB, Abb, AAI) of the tissue weighting factor proved difficult in practice due to lack of quantitative data. Because of this several distributions were considered. The results of the analysis give a mean value of w(lung) H(lung) per unit exposure to radon progeny in the home of 15 mSv per working level month (WLM) for a population. For a given radon gas concentration, the mean value of w(lung) H(lung) per unit exposure is 13 mSv per 200 Bq.m(-3).y of 222Rn. Parameters characterising the distributions of w(lung) H(lung) per unit exposure are given. If the ICRP weighting factors are fixed at their default values (ABB, Abb, AAI = 0.333, 0.333, 0.333; w(lung) = 0.12; and wr = 20) then on the basis of this uncertainty analysis it is extremely unlikely (P approximately 0.0007) that a value of Hw/Pp for exposure in the home is as low as 4 mSv per WLM, the value determined with the epidemiological approach. Even when the uncertainties in the ABB, Abb, AAI, values are included then this probability is predicted to be between 0.01 to 0.08 depending upon the distribution assumed for describing the uncertainties in the ABB, Abb, AAI, values. Thus, it is concluded that the uncertainties in the HRTM parameters considered in this study cannot totally account for the discrepancy between the dosimetric and epidemiological approaches.

Administration, Inhalation↗
PubMed2003

Metakaolin as a radon retardant from concrete.

Granite aggregates are known to be the radon source in concrete. Recently, metakaolin has been introduced as a partial substitution of Portland cement to produce high strength concrete. It can effectively reduce the porosity of both the matrix and the aggregate/paste transition zone, which suggests its ability to retard radon emission from concrete aggregates. In the present work, radon exhalation rates from concrete cubes substituted with metakaolin were measured using charcoal canisters and gamma spectroscopy, and were considerably lower than those from normal concrete, by about 30%. The indoor radon concentration reduction is estimated as approximately 9 Bq m(-3) calculated using a room model, causing a 30% reduction in the indoor radon concentration and the corresponding radon dose. Therefore, metakaolin is a simple material to reduce the indoor radon concentration and the radon dose.

Air Pollutants, Radioactive↗
PubMed2003

Calibration of LR-115 for 222Rn monitoring taking into account the plateout effect.

The dose received by people exposed to indoor radon is mainly due to radon progeny. This fact points to the establishment of techniques that access either radon and progeny together, or only radon progeny concentration. In this work a low cost and easy to use methodology is presented to determine the total indoor alpha emission concentration. It is based on passive detection using LR-115 and CR-39 detectors, taking into account the plateout effect. A calibration of LR-115 track density response was done by indoor exposure in controlled environments and dwellings, places where 222Rn and progeny concentration were measured with CR-39. The calibration factor obtained showed great dependence on the ambient condition: (0.69 +/- 0.04) cm for controlled environments and (0.43 +/- 0.03) cm for dwellings.

Air Pollutants, Radioactive↗
PubMed2003

Seasonal correction factors for estimating radon exposure in dwellings in France.

Indoor radon concentrations are subject to seasonal variation with a maximum in winter and a minimum in summer. Procedures to correct for seasonal variation are necessary in order to get an unbiased estimate of the annual average radon concentration from data based on short-period radon measurements. To obtain correction factors, we apply the model developed by Pinel et al to the French database of indoor radon measurements (measurements performed as part of the indoor radon case-control study and of the national radon measurement campaign). For 6-month measurements, the correction factors vary from 0.87 to 1.17 and agree with those previously published. These results might be applicable when assessing indoor radon concentrations with regard to recommended action levels.

Air Pollutants, Radioactive↗
PubMed2003

The weekly measurement deviations of indoor radon concentration from the annual arithmetic mean.

The difference between weekly measurements and the annual arithmetic mean of radon indoor concentration CRn,Indoor was studied in the Czech Republic. The deviations were analysed for 1537 weekly measurements which were consecutively obtained in 29 rooms over a period of 1 year and the annual arithmetic mean was calculated for each particular room. The relationship of the deviations to three meteorological parameters (i.e. outside temperature, atmospheric pressure, and weekly rainfall) and to the sequential number of a calendar week was studied. The effect of atmospheric pressure and weekly rainfall was not significant. The deviation between a weekly measurement and the annual arithmetic mean depended significantly on outside weekly average temperatures. If the average outside weekly temperature was below 10 degrees C, the radon concentration was systematically higher than that of the annual arithmetic mean. The deviation variability was lower up to a temperature of 10 degrees C. If the weekly average outdoor temperature was higher than 10 degrees C, the uncertainty of a weekly measurement of radon concentration was also higher.

Air Pollutants, Radioactive↗
PubMed2003

Characteristics of radon and its progeny concentrations in air-conditioned office buildings in Tokyo.

A series of measurements were carried out to understand the characteristics of radon and its progeny in air-conditioned office buildings. Long-term measurements of radon were made with etched track detectors. Continuous measurements of radon and its progeny concentrations were also conducted in some buildings to study their temporal variations. The results show that radon and its progeny concentrations routinely varied along with the working activities. They are generally low while people are working, due to air conditioning, whereas they rise steadily after the air conditioning stops. When considering action levels not only in homes but also workplaces, attention should be paid to annual doses from the viewpoint of radiation protection. The annual dose is generally estimated with a long-term measurement of radon concentration using a passive device such as an etched track detector. Since its reading corresponds to a long-term average concentration regardless of working hours, but, the annual dose will be overestimated. When comparing a real dose after considering the working hours, they differ by a factor of more than 2.

Air Conditioning↗
PubMed2003

Thermal diffusion of radon in porous media.

Based on the non-intersection model of cylindrical capillaries, the mean radius of the pores of some soils and building materials are estimated. In size, the above-mentioned radii are usually of the order of the free path of gas molecules at atmospheric pressure. A review of pore size distribution data also reveals that a large fraction of concrete pores belong to Knudsen's region. This fact indicates that the thermal gradient in these media must cause gas (radon) transport. The interpretation of the experimental data concerning the rate of emanation of 222Rn from a concrete-capped source subjected to a sudden increase in temperature is given, based on irreversible thermodynamics theory. The calculations given here for radon flux, caused by concentration and thermal gradients, are in satisfactory agreement with the experimental data. It is shown that thermodiffusion can significantly contribute to radon flux in concrete. The need to include the thermodiffusion radon flux in the radon entry model is discussed.

Air Pollutants, Radioactive↗
PubMed2003

Indoor radon levels and lung cancer risk estimates in seven cities of the Bahawalpur Division, Pakistan.

Indoor radon concentration levels were measured in seven major cities of the Bahawalpur Division, Pakistan. These included Fort Abbas, Minchin Abad, Hasilpur, Bahawalpur, Liaqatpur, Rahimyar Khan and Sadiq Abad. In order to select houses for this survey, the inhabitants were approached through their school-registered children. Due to several constraints, only those 100 houses were chosen in each city that were relatively the best representatives of the built-up area. The selected houses were then divided into live categories according to the house locations and building characteristics. CR-39 detectors, placed in polyethylene bags. were installed at head height in bedrooms and sitting rooms of all the selected houses and were exposed to radon and its daughter products for 90 days. Four such measurements were performed over a year in order to average out the seasonal variation in radon levels. After exposure, all the detectors were etched and counted under an optical microscope. The track densities of four measurements were averaged out and related to radon concentration levels. The radon levels were found to be 20, 20, 26, 28, 34, 42, 47 Bq m(-3) in the bedrooms and 24, 26, 27, 26, 37, 40, 43 Bq m(-3) in sitting rooms of Hasilpur, Rahimyar Khan, Minchin Abad, Fort Abbas, Sadiq Abad, Bahawalpur and Liaqatpur respectively. The observed variation in the radon level may be attributed to the geological variation in the area. Based on the observed data, excess lung cancer risk was assessed using the risk factors recommended by the USEPA, UNSCEAR and the ICRP. According to the EPA model, the lifetime excess lung cancer risk due to the lifetime exposure is found to vary from 12-102 per million per year in the houses surveyed. This variation is from 16-114 and 26-62 per million per year if UNSCEAR and ICRP limits are applied respectively.

Air Pollutants, Radioactive↗
PubMed2001

Extended survey of indoor and outdoor terrestrial gamma radiation in Greek urban areas by in situ gamma spectrometry with a portable Ge detector.

The results obtained from more than 1000 indoor and outdoor in situ gamma spectrometry measurements in 41 towns (from all geographic subdivisions) of the Greek mainland (not islands) are presented. From the in situ gamma spectra the absorbed dose rate in air due to uranium series, thorium series, 40K and 137Cs are derived and discussed.

Air Pollutants, Radioactive↗
PubMed2001

Physical parameters and dose factors of the radon and thoron decay products.

The dose per exposure unit of the short-lived radon and thoron decay products was calculated using a dosimetric approach. The calculations are based on a lung dose model with the structure that is related to the ICRP 66 respiratory tract model. The dose relevant parameters, unattached fraction of the decay product clusters (fp) and size distribution of the unattached and aerosol-attached decay products for different living and working places are reported. Taking into account these characteristics the dose conversion factors (DCF) of the radon and thoron decay products were estimated. In addition, the living and working places were divided concerning their aerosol parameters like particle number concentration and activity size distribution.

Aerosols↗
PubMed2001

Indoor radon concentrations in Poland as determined in short-term (two-day) measurements.

The aim of the present work was to obtain a pattern of 222Rn concentration distributions in typical buildings in Poland. In the investigations, the environmental passive detectors of the PICO-RAD type were used. The study encompassed buildings that were typical for Poland. The distribution of airborne 222Rn concentrations indoors is of a log-normal type. A total 1171 detectors were measured. Measurements were made in 319 basements, the remaining 852 measurements were carried out in the inhabited part of the houses. The radon concentrations in the basements in Bq x m(-3) ranged from 6 to 1300 with the arithmetic mean AM = 60, geometric mean GM = 30 and median M = 28, whereas those in the inhabited parts of the house (above the ground level) were: AM = 25, GM = 17 and M = 16 with the highest record value of 420.

Air Pollutants, Radioactive↗
PubMed2001

In progress identification of radon prone areas: Toscana and Veneto.

Two studies aimed at defining radon prone areas in Toscana and Veneto, based on indoor measurements, are merged in this paper to extract the key points for a possible general methodology. In territorial units, the geometric mean (GM) and standard deviation (GSD) are evaluated from empirical data and the fraction of dwellings above the reference level (RL) is derived according to a log-normal model. In Toscana the sampling base is made of nearly 1,000 measurements (dwellings and kindergartens), apportioned according to the lithological classes (22) of the region. In Veneto 1,230 measurements in dwellings of the upper part of the region (estimates are given for the south), have been assigned to 6 x 5 km2 sequential units of the territory: the detection floor has been considered and results are referred to the regional mean dwellings condition with respect to the floor. Empirical GM and GSD values are corrected to increase statistical power based on two different methods. Maps of the percentages of dwellings with more than 200 Bq x m(-3) are presented. Areas with magmatic rocks in southern Toscana and northern parts of Vicenza and Belluno provinces in Veneto clearly emerge with more than 10% of dwellings above 200 Bq x m(-3). Efforts are required to establish proper confidence limits for estimates and to trace radon maps upon an administrative basis.

Air Pollutants, Radioactive↗
PubMed2004

Radon progeny size distributions and enhanced deposition effects from high radon concentrations in an enclosed chamber.

Prior work studying radon progeny in a small enclosed chamber found that at high (222)Rn concentrations an enhanced surface deposition was observed. Subsequent measurements for unfiltered air showed minimal charged particle mobility influence. Progeny particle size measurements reported here, performed at the US Department of Energy Environmental Measurement Laboratory (now with Home Security Department), using the EML graded screen array (GSA) system show in unfiltered air that the high (222)Rn levels causes a reduction in the attached (218)Po progeny airborne particulates and formation of additional normal sized unattached ( approximately 0.80 nm) and also even smaller (218)Po below 0.50 nm. At a (222)Rn level of 51 kBq m(-3), 73% of all (218)Po are of a mean particle diameter of about 0.40 +/- 0.02 nm. At this (222)Rn level, the ratio of (218)Po to (222)Rn airborne concentrations is reduced significantly from the concentration ratio at low (222)Rn levels. Similar reductions and size reformations were observed for the (214)Pb and (214)Bi/Po progeny. The particle size changes are further confirmed using the plateout rates and corresponding deposition velocities. The Crump and Seinfeld deposition theory provides the corresponding particle diffusion coefficients. With the diffusion coefficient to ultrafine clustered particle diameter correlation of Ramamurthi and Hopke, good agreement is obtained between EML GSA and deposition velocity data down to 0.40 nm. Strong evidence is presented that the progeny size reduction is due to, as a result of air ionization, the increased neutralization rate (primarily from electron scavenging of OH molecules) of the initially charged progeny. This is shown to increase with the (1/2) power of (222)Rn concentration and relative humidity as well as increased air change rate in the chamber. These results imply that at (222)Rn levels above 50 kBq m(-3), at relative humidity of 52%, a considerable reduction in lung dose could occur from preferential deposition of the progeny in the nasal and oral passages.

Adsorption↗