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PubMed2004

Uranium-238 and thorium-232 series concentrations in soil, radon-222 indoor and drinking water concentrations and dose assessment in the city of Aldama, Chihuahua, Mexico.

High-resolution gamma spectrometry was used to determine the concentration of 40K, 238U and 232Th series in soil samples taken from areas surrounding the city of Aldama, in Chihuahua. Results of indoor air short-time sampling, with diffusion barrier charcoal detectors, revealed relatively high indoor radon levels, ranging from 29 to 422 Bq/m3; the radon concentrations detected exceeded 148 Bq/m3 in 76% of the homes tested. Additionally, liquid scintillation counting showed concentrations of radon in drinking water ranging from 4.3 to 42 kBq/m3. The high activity of 238U in soil found in some places may be a result of the uranium milling process performed 20 years ago in the area. High radon concentrations indoor and in water may be explained by assuming the presence of uranium-bearing rocks underneath of the city, similar to a felsic dike located near Aldama. The estimated annual effective dose of gamma radiation from the soil and radon inhalation was 3.83 mSv.

Air Pollutants, Radioactive↗
PubMed2006

Radiological studies in the hot spring region of Mahallat, Central Iran.

Five hot springs called 'Abegarm-e-Mahallat', located in the central part of Iran, have a mean water temperature of 46 +/- 1 degrees C and are used by visitors as spas. This is an area of high natural radiation background due to the presence of (226)Ra and its decay products in the deposited travertine (CaCO(3)). The mean concentration of (226)Ra in these hot springs, measured by the emanation method, ranged from 0.48 +/- 0.05 to 1.35 +/- 0.13 Bq l(-1). (222)Rn concentrations measured in the hot springs using a liquid scintillation counter ranged from 145 +/- 37 to 2731 +/- 98 Bq l(-1). Mean radon concentrations in air were 487 +/- 160 and 15.4 +/- 2.7 Bq m(-3) for indoor and outdoor, respectively. Radiation levels above that of normal background ( approximately 100 nGy h(-1)) were mainly limited to the Quaternary travertine formations in the vicinity of the hot springs. The results of environmental radiological studies in this region are presented and discussed.

Air Pollutants, Radioactive↗
PubMed1998

Comparative studies of indoor radon concentration levels in Jordan using CR-39 based bag and cup dosimeters.

Indoor radon concentration levels have been measured in 9 major cities of Jordan using CR(-3)9 detectors placed in punched polyethylene bags to measure both radon and thoron, and in cups to measure radon only. The average value of indoor radon and thoron concentration levels measured with bag dosimeters vary from 32 to 107 Bq m(-3) and the indoor radon concentration levels measured with cup dosimeters vary from 27 to 88 Bq m(-3). The indoor radon concentration levels in Irbid and Zaraka are comparable to the world average of 27 Bq m(-3). In Ajloun, Jerash, Salt, Tafilah and Amman, the indoor radon levels are greater than the world average by a factor of up to 2, and in Madaba and Karak these levels are greater than the world average by a factor of more than 3. The large variation in the measured radon levels may be attributed to the large variation in the 226Ra activity in the soil of the region.

Air Pollutants, Radioactive↗
PubMed2004

Natural radiation doses to the population in a granitic region in Spain.

The global average effective dose from natural radiation sources is estimated to be 2.4 mSv y(-1). Nevertheless, local variations in the radiation exposure may differ by orders of magnitude. In this paper, we study a rural area in western Salamanca (Spain) where doses are potentially well above the stated average value. Its geology consists mostly of granite and schist, presenting various uranium mineralisations, some of which were exploited in former years. Water samples, both surface and groundwater, were collected in selected villages and measured by liquid-scintillation spectrometry. 222Rn in dwellings was determined in dwellings by means of short-term measurements, using Picorad vials and long-term measurements with CR-39 detectors. The committed effective doses to the inhabitants due to indoor 222Rn and 222Rn and 226Ra in drinking water were assessed using the dose conversion factors proposed in the UNSCEAR 2000 report.

Air Pollutants, Radioactive↗
PubMed2003

Indoor radon levels in buildings in the Autonomous Community of Extremadura (Spain).

Indoor air samples taken in buildings throughout the provinces of Cáceres and Badajoz in the Autonomous Community of Extremadura, Spain, were analysed for airborne radon concentrations using charcoal canisters. Measurements were made during the years 1998-2000. The geometrical mean indoor concentration was 90 Bq m(-3). An estimated annual effective dose of 1.6 mSv y(-1) was calculated for residents, assuming an equilibrium factor of 0.4 and an occupancy factor of 0.8. The relative importance of the principal variables that condition radon concentrations inside buildings was also delimited experimentally. These were: soil type, construction materials used, the height of the room above ground level, and the degree of ventilation. The temporal evolution of the radon concentration was analysed, as this aspect could be particularly important in a Continental-Mediterranean climate such as that of the two provinces of the study.

Air Pollutants, Radioactive↗
PubMed2005

Radon-prone areas in the Lombard plain.

This paper reports the results of indoor radon measurements carried out in the Lombard plain. The aim of this study, which is based on the geological context, was to identify radon high-risk areas. The underlying geology has been established by means of the available stratigraphies giving a schematic representation of the sites in which either occurrence of gravel or silt and clay predominate with depths ranging from 0 to 50 m. Radon measurements were performed in a sample of 411 one-family houses in seven villages located in the southern area of Bergamo and Brescia. The findings indicate that when the substrate is dominated by clay, radon concentration for dwellings on the ground floor are low, whereas a strong predominance of underlying gravel mixed up in sand gives in winter months high radon flux from underground.

Air Pollutants, Radioactive↗
PubMed2004

Variation in indoor thoron levels in Mexico City dwellings.

This paper presents the results obtained for thoron concentration in 50 single-family dwellings in normal occupancy conditions (open house conditions), measured by a passive electret system (type E-PERM, SSTB configuration) in a 2001-2002 monitoring survey in the Metropolitan Zone of Mexico City. The results show the general log-normal distribution of integrated indoor thoron concentration with annual arithmetic and geometric means of 82 and 55 Bq m(-3), respectively, with ranges from 8 to 234 Bq m(-3) higher than world average of 3 Bq m(-3). The seasonal variation shows the minimum mean values in the summer season that were 35% lower than in autumn.

Air Pollutants, Radioactive↗
PubMed2003

Long-term measurements of radon equilibrium factor in Greek dwellings.

The time variation of the radon equilibrium factor F was measured every four hours in the Nuclear Technology Laboratory of the Aristotle University of Thessaloniki (in northern Greece) during October 1998-April 1999. The time dependence of the mean weekly value of radon equilibrium factor F is relatively small. During October 1999-May 2000 the radon equilibrium factor was measured in 25 apartments randomly distributed in Thessaloniki. The mean value of the equilibrium factor F is 0.47 +/- 0.09, close to the typical value of 0.4 adopted by UNSCEAR.

Air Pollutants, Radioactive↗
PubMed1993

Video display terminals and radon.

Recent reports indicate that video display terminals (VDTs) can collect radon progeny from the air. This occurs especially when they are turned off and may have negative electric fields which attract positively charged radioactive dust. We have studied this phenomenon in detail and evaluated various techniques for removing the gettered radioactivity while the video display terminal is both off and on. We have evaluated what happens when the video display terminal is switched, thereby reversing the electric field near the screen. We have also studied possible inhalation effects by a video display terminal operator during field reversal and find that although some radioactivity may be released during the cycle, room air currents redistribute it into the room with no detectable levels being inhaled by users.

Air Pollutants, Radioactive↗
PubMed2004

Waterborne radon in seven Maine schools.

This study investigated the transfer coefficient of radon from water to air in kitchens and bathrooms for seven schools located in Maine. Simulations occurred in water use rooms containing multiple airborne radon detectors. Quantities measured included radon concentration in water (10-960 Bq L(-1), 260-26,000 pCi L(-1)), air (0-3 Bq L(-1), 0-80 pCi L(-1)), volume of water used, emissivities (0.04-0.98), and ventilation rates (0.012-0.066 min). Using these parameters provides the means for calculating the transfer coefficient and by which dose due to waterborne radon can be estimated in other schools. Transfer coefficient values calculated for kitchens and baths ranged from 9.6 x 10(-6) to 2.0 x 10(-2). Multiple detectors showed that the radon concentration varied throughout a room. These measurements represent the first of this type to be done in schools in Maine.

Air Movements↗
PubMed2004

Radon exposure in the thermal spas of Lesvos Island--Greece.

The aim of this work is to study the exposure due to radon to bathers and personnel in the spas of Lesvos Island under a specific use pattern. 222Rn concentrations in the supplying water were measured during a long time period. Variations in indoor 222Rn, attached and unattached progenies, and influence of the ambient atmosphere were thoroughly analysed during bath treatment for the purpose of investigating a consequent probable short-term health impact. Concentration peaks both for 222Rn and PAEC were found to appear during bathtubs filling. These peaks considered imposing an additional short-term radiation burden for spa users. The additional doses delivered to bathers during bath treatment were found to be very low and for personnel did not exceed the value of 5 mSv per year.

Air Pollutants, Radioactive↗
PubMed2006

Radon-thoron discriminative measurements in Gansu Province, China, and their implication for dose estimates.

Indoor radon measurements were carried out in cave dwellings of the Chinese loess plateau in Gansu province, where previously the Laboratory of Industrial Hygiene (LIH), China, and the U.S. National Cancer Institute (NCI) had conducted an international collaborative epidemiological study. The LIH-NCI study showed an increased lung cancer risk due to high residential radon levels, and estimated the excess odds ratio at 100 Bq/m3 to be 0.19 (Wang et al., 2002). The present study used two types of newly developed passive monitors: One is a discriminative monitor for radon and thoron; the other is a selective monitor for thoron decay products. The arithmetic mean concentrations of indoor radon and thoron were 91 and 351 Bq/m3, respectively. As reported by our previous study in Shanxi and Shaanxi provinces (Tokonami et al., 2004), the presence of high thoron concentration was confirmed and thoron was predominant over radon in the cave dwellings. However, the mean equilibrium equivalent thoron concentration (EETC) was found to be much lower than expected when assuming the equilibrium factor of 0.1 provided by the UNSCEAR (2000) report. The effective dose by radon and thoron decay products was estimated to be 3.08 mSv/yr. It was significantly lower than the dose of 8.22 mSv/yr estimated from the measurements that did not take into consideration any discrimination between radon and thoron. Excess relative risk of lung cancer per sievert may be much higher than the risk estimated from the LIH-NCI study, considering that discriminative measurements were not used in their study.

Air Pollutants, Radioactive↗
PubMed2004

Twenty years of experience in monitoring 41Ar in a research reactor and decrease of its discharge into the environment.

The radioactive gas 41Ar has been produced at high concentration by neutron activation near the reactor core in the Kyoto University Research Reactor. A pipe line for an exhaust stream, so-called sweep gas, was fabricated at the construction of the reactor in 1964 in order to exhale 41Ar from the facilities above to the environment. Other exhaust lines with decay tanks were established separately from the sweep line for both the cold neutron source in 1986 and the heavy-water tank in 1996, respectively, because a higher amount of 41Ar was thought to be produced from these facilities due to the improvement. As a result, a slight change in the flow rate of the exhaust was found to have a great deal of influence on both the 41Ar concentration in the reactor room and the rate of emission from the stack. By monitoring the exhaust air from the decay tanks, the mechanism for decreasing the emission was clarified together with identifying an obstacle, i.e., the condensate against the steady state flow, formed in the exhaust pipe. By setting the flow rate suitably in the exhaust line, the rate of 41Ar emission from the biological shielding into both the work place in the reactor room and the environment has been controlled as low as reasonably achievable.

Air Pollutants, Radioactive↗
PubMed2003

A quantitative method for optimized placement of continuous air monitors.

Alarming continuous air monitors (CAMs) are a critical component for worker protection in facilities that handle large amounts of hazardous materials. In nuclear facilities, continuous air monitors alarm when levels of airborne radioactive materials exceed alarm thresholds, thus prompting workers to exit the room to reduce inhalation exposures. To maintain a high level of worker protection, continuous air monitors are required to detect radioactive aerosol clouds quickly and with good sensitivity. This requires that there are sufficient numbers of continuous air monitors in a room and that they are well positioned. Yet there are no published methodologies to quantitatively determine the optimal number and placement of continuous air monitors in a room. The goal of this study was to develop and test an approach to quantitatively determine optimal number and placement of continuous air monitors in a room. The method we have developed uses tracer aerosol releases (to simulate accidental releases) and the measurement of the temporal and spatial aspects of the dispersion of the tracer aerosol through the room. The aerosol dispersion data is then analyzed to optimize continuous air monitor utilization based on simulated worker exposure. This method was tested in a room within a Department of Energy operated plutonium facility at the Savannah River Site in South Carolina, U.S. Results from this study show that the value of quantitative airflow and aerosol dispersion studies is significant and that worker protection can be significantly improved while balancing the costs associated with CAM programs.

Aerosols↗
PubMed2001

Exposure of red bone marrow to ionising radiation from natural and medical sources in France.

This paper presents a review of available data on the average level of equivalent dose to the red bone marrow in France, due to natural and some medical exposures. The sources of exposure to ionising radiation which were studied are medical examinations involving x-rays (diagnostic radiology), inhalation of radon and thoron, cosmic irradiation, terrestrial irradiation and intakes of natural radionuclides. This review is based, where possible, on specific data for France. The influence of age on exposure levels is studied when data are available. The total equivalent dose to the red bone marrow is estimated at 2.4 mSv year(-1), 2.7 mSv year(-1) and 5.4 mSv year(-1) respectively for adults (> or =18 years old), children (3-17 years old) and infants (0-1 year old). The high level of exposure for infants is explained by the important contribution of 210Po. The average equivalent dose to the red bone marrow for adults is also compared with the average committed effective dose due to the same exposure sources. The importance of medical exposure and natural exposure due to intake of natural radionuclides emphasises the importance of obtaining more information about these sources of exposure.

Adolescent↗
PubMed2005

The EXPURT model for calculating external gamma doses from deposited material in inhabited areas.

EXPURT, NRPB's model for calculating external gamma doses in inhabited areas, was originally developed in the mid-1980s. Deposition on surfaces in the area, the subsequent transfer of material between different surfaces or its removal from the system, and dose rates in various locations from material on the different surfaces are modelled. The model has been updated to take account of more recent experimental data on the transfer rates between surfaces and to make it more flexible for use in assessing dose rates following an accidental release. EXPURT is a compartmental model and models the transfer of material between the surfaces using a set of first order differential equations. It enables the impact of the decontamination of surfaces on doses and dose rates to be explored. The paper describes the EXPURT model and presents some preliminary results obtained using it.

Air Pollutants, Radioactive↗
PubMed2005

Urban dose rates at Gävle, Göteborg and Lund.

Besides gamma rays from 137Cs emanating from the Chernobyl accident, gamma rays from natural radionuclides are a dominant source of radiation exposure to the public. Since people spend much more time indoors than outdoors the radiation dose obtained inside dwellings contributes greatly to individual and collective doses. Dose rate measurements were made at 20 locations within the city of Göteborg and at further 22 reference sites within a radius of 100 km. Measurements were also made at Gävle and Lund. The dose rates were measured with RNI intensimeters, TLD (LiF) meters and in in situ measurements using an HPGe. The ground cover was grass, asphalt, concrete slates or paving-stones. The dose rates varied between 0.05 and 0.25 microSv/h. Also performed in different ways, measurements made inside and outside buildings at both Göteborg and Gävle showed inside dose rates higher than outside dose rates.

Air Pollutants, Radioactive↗