Temporal variation of thoron decay product concentration in the atmosphere and comparison with radon decay product concentration

Seasonal and long-term variation of the airborne ²¹²Pb concentration, representative of the equilibrium equivalent concentration of thoron decay products (EEC_Rn220), was investigated from 1989 through 1996 at a semi-natural location in southern Germany. Continuous measurement yielded a long-term average concentration of 0.082 Bq m^–3, while daily mean concentrations varied from ≤0.01 to 0.34 Bq m^–3. An average annual effective dose of 1.4 mSv due to outdoor thoron progeny concen-tration was estimated. This is about 2% of the dose due to the average short-lived radon progeny concentration (EEC_Rn222) of 8.4 Bq m^–3 measured for this location in the same period. In most years the seasonal pattern of ²¹²Pb activity concentration in the atmosphere is characterized by two maxima: the first in May and the second one in September. Low concentrations are observed from November through February of each year. This is in contrast to the behaviour of the short-lived ²²²Rn progeny which exhibit enhanced concentrations exactly during these months. The most probable reason for the different temporal behaviour of ²¹²Pb is the extremely reduced flux of thoron gas from the ground during the winter months. Received: 19 August 1997 / Accepted in revised form: 22 January 1998     

Air quality monitoring with regard to222Rn in buildings constructed on disused tin-mining areas

Secondary land uses have taken place on disused tin-mining areas in the form of mixed development projects consisting of housing schemes with commercial and recreational facilities. The cassiterite minerals containing tin are rich in thorium and uranium found in the xenotime and monazite minerals commonly present in the Malaysian terrains. With the upheaval of these minerals from tin-mining activities, the environment is basically exposed to the natural radioactive materials derived from the²³²Th and²³⁸U radionuclides. One of the daughter products is²²²Rn and it is known to be one of the main indoor air pollutants related to the sick-building syndrome. High concentrations of indoor²²²Rn will be hazardous to human health, which is often associated to lung cancer and other chronic diseases. The main purpose of this study is to determine the concentrations of indoor²²²Rn in residential areas constructed on former tin-mining areas with particular reference to places with high human activities such as commercial areas. Air samples were collected using the RDX-013 scintillator cell and the quantitity of²²²Rn determined by the RDA-200 radon/thoron detector. Measurements were made at different times and intervals for the purpose of looking at variations of²²²Rn levels present in the atmosphere. Results of this study showed that the concentration of indoor²²²Rn is higher in the morning (1.64 ± 0.20 pCi L) compared to the levels detected in the afternoon (1.30 ± 0.08 pCi L) for most residential areas. As expected, the concentration of²²²Rn outdoors is lower (1.08 ± 0.08 pCi L) compared to the concentration determined indoors (1.64 ± 0.20 pCi L). Recently constructed houses or buildings in commercial centers seemed to have²²²Rn concentrations relatively higher than those occupied for longer periods of time. However, the levels of²²²Rn concentrations in the study area showed that all were below the maximum permissible level of 4.0 pCi L as stipulated by the United States Environmental Protection Agency. This work also discussed the mitigation measures taken by the building management of commercial buildings to reduce the risk of²²²Rn buildup in an effort to improve public health as a result of the poor indoor air quality.     

Thoron levels in traditional Chinese residential dwellings

A survey on radon (²²²Rn), thoron (²²⁰Rn) and its decay products (²²⁰RnD) was conducted in Chinese traditional residential dwellings constructed with loam bricks or soil wall. The activity concentrations in 164 dwellings under investigation were 72.4±59.2 (arithmetic mean, AM) and 57.5±2.0 Bq m⁻³ (geometric mean, GM) for ²²²Rn, and 318±368 and 162±3.7 Bq m⁻³ for ²²⁰Rn, respectively. For ²²⁰RnD, 67 dwellings were studied. The AM of the ²²⁰RnD equilibrium equivalent concentration was 3.8±3.3 Bq m⁻³ with a maximum value of 15.8 Bq m⁻³. On the basis of these results, the average annual effective doses to the local residents due to radon and thoron exposure were 1.44–4.62 mSv. Thoron contributes 12.9–56.6% to the total doses. Preliminary results show that there is a relation between ²²⁰RnD in air and ²³²Th in soil. The correlation factors of outdoor and indoor were 0.88 and 0.40. The ²³²Th activity content of Chinese soil is estimated to be about two times the world average. The traditional residential dwellings with soil construction are still common in China. Further investigations on the ²²⁰Rn level in these dwelling with the aim of dose reduction are proposed.     

Radiation doses to individuals due to 238U, 232Th and 222Rn from the immersion in thermal waters and to radon progeny from the inhalation of air inside thermal stations

In Morocco, thermal waters have been used for decades for the treatment of various diseases. To explore the exposure pathway of ²³⁸U, ²³²Th and ²²²Rn to the skin of bathers from the immersion in thermal waters, these radionuclides were measured inside waters collected from different Moroccan thermal springs, by means of CR-39 and LR-115 type II solid-state nuclear track detectors (SSNTDs), and corresponding annual committed effective doses to skin were determined. Accordingly, to assess radiation dose due to radon short-lived decay products from the inhalation of air by individuals, concentrations of these radionuclides were measured in indoor air of two thermal stations by evaluating mean critical angles of etching of the CR-39 and LR-115 II SSNTDs. Committed effective doses due to the short-lived radon decay products ²¹⁸Po and ²¹⁴Po by bathers and working personnel inside the thermal stations studied were determined.     

Spatial distribution of 222Rn concentrations and dose estimations in various waters

In this article, the levels of ²²²Rn concentrations, annual effective doses, and excess lifetime cancer risk estimations were investigated for water samples in the city of Osmaniye, located in the southern part of Turkey. The measurements were conducted using a radon gas analyzer (AlphaGUARD PQ 2000 PRO). The arithmetic average of ²²²Rn concentrations was 0.44 Bq.L^?1 with a geometric standard deviation of 0.19 and geometric average 0.41 Bq.L^?1. The results obtained were compared with the findings of other studies. All measured radon concentrations were below the values recommended by the World Health Organization and the U.S. Environmental Protection Agency. The associated radiological parameters such as annual effective doses (AED) and excess lifetime cancer risk (ELCR) from consumption of these waters were calculated. The computed average annual effective doses for ingestion and inhalation as well as excess lifetime cancer risk were estimated to be 1.13 μSv.y^?1, 1.10 μSv.y^?1, and 3.95 × 10^?6, respectively. ²²²Rn concentration, AED, and ELCR interpolated values of the region were determined and mapped using the Kriging method. The results of radon concentrations in this study provide a data baseline for future studies on subsequent evaluations of possible future environmental contamination of Osmaniye Province.     

Doses from beta radiation in sensitive layers of human lung and dose conversion factors due to <Superscript>222</Superscript>Rn/<Superscript>220</Superscript>Rn progeny

Great deal of work has been devoted to determine doses from alpha particles emitted by ²²²Rn and ²²⁰Rn progeny. In contrast, contribution of beta particles to total dose has been neglected by most of the authors. The present work describes a study of the detriment of ²²²Rn and ²²⁰Rn progeny to the human lung due to beta particles. The dose conversion factor (DCF) was introduced to relate effective dose and exposure to radon progeny; it is defined as effective dose per unit exposure to inhaled radon or thoron progeny. Doses and DCFs were determined for beta radiation in sensitive layers of bronchi (BB) and bronchioles (bb), taking into account inhaled ²²²Rn and ²²⁰Rn progeny deposited in mucus and cilia layer. The nuclei columnar secretory and short basal cells were considered to be sensitive target layers. For dose calculation, electron-absorbed fractions (AFs) in the sensitive layers of the BB and bb regions were used. Activities in the fast and slow mucus of the BB and bb regions were obtained using the LUNGDOSE software developed earlier. Calculated DCFs due to beta radiation were 0.21 mSv/WLM for ²²²Rn and 0.06 mSv/WLM for ²²⁰Rn progeny. In addition, the influence of Jacobi room parameters on DCFs was investigated, and it was shown that DCFs vary with these parameters by up to 50%.     

Rapid determination of radon daughters and of artificial radionuclides in air by online gamma-ray spectrometry

For the determination of airborne radionuclide concentrations in real time, a fixed filter device was constructed which fits directly onto a germanium detector with standard nuclear electronics and a multichannel analyzer buffer connected via a data line to a personal computer for remote control and on-line spectrum evaluation. The on-line gamma-ray spectrometer was applied to the study of radon decay product concentrations in ground-level air and to the rapid detection of any contamination of the environmental air by artificial radionuclides. At Munich-Neuherberg, depending on the meteorological conditions, the measured air concentrations of²¹⁴Pb, the first gamma-ray-emitting member of the²²²Rn decay series, varied from about 1 to 50 Bq m^–3. For the artifical radionuclides⁶⁰Co,¹³¹I and¹³⁷Cs the detection limits were determined as a function of the varying natural radon daughter concentrations at sampling and counting times of 1 h or 1 day. For these radionuclides minimum detectable air activity concentrations of 0.3 or 0.001 Bq m^–3, respectively, were obtained at low radon daughter levels. At high radon daughter levels the respective detection limits were found to be higher by a factor of only about 2.Dedicated to Prof. Wolfgang Jacobi on the occasion of his 65th birthday     

Distribution of 222Rn in groundwater and estimation of resulting radiation dose to different age groups: A case study from Bangalore City

Ingesting waters holding high levels of natural occurring radioactive element like Radon would contribute to increase in the effective dose received by people followed by an increased prevalence of cancer. The current study is an attempt to describe the extent of contribution of ²²²Rn to natural background radiation and the resultant effective dose to public of different age groups. In order to do so, 65 groundwater samples from selected parts of Bangalore city were collected and analyzed for radon activity using RAD7 radon monitor coupled with RAD H₂O accessories. The radon activity was in the range of 3.05–696 Bq/L (mean: 91.39 Bq/L) and 92.31% of the groundwater samples recorded elevated radon concentration above the United States environmental protection agency (USEPA's) Maximum Contaminant Level (MCL) value of 300 pCi/L, corresponding to 11.1 Bq/L. The mean annual effective dose contribution of people falling under different age groups (viz., infants, children, teens: males and females, adults: males and females, pregnant and lactating women) due to ingestion of water-borne ²²²Rn ranged from 0.082 to 0.444 mSv/y and was found to be higher in all the age groups of males compared to respective female age groups, but well within the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and World Health Organization (WHO) proposed limit of 1 mSv/y.     

Radon in Norwegian dwellings and the feasibility of epidemiological studies

Summary The results of a pilot study on radon in Norwegian dwellings are presented together with a discussion on the feasibility of an epidemiological study on the correlation between lung cancer and radon progeny exposure in dwellings. There are large variations in the mean radon concentration in Norwegian municipalities, and the population average indoor radon concentration is high (80–100 Bq m^–3). The large variations and high absolute values, together with excellent lung cancer and smoking habit data, make it feasible to conduct epidemiological studies based on representative exposure data in the Norwegian population.     

Assessments of 226Ra and 222Rn concentration in well and tap water from Sik,Malaysia, and consequent dose estimates

Abstract

The ingestion of ²²⁶Ra, inhalation, and ingestion of ²²²Rn in water is considered the primary health risk for lungs and stomach. This study presents the concentrations of ²²⁶Ra and ²²²Rn in well and tap water collected from Sik, Malaysia, using HPGe and RAD7 detectors. Maximum average concentrations of ²²⁶Ra and ²²²Rn were found 47.6?±?3.6 mBq/l and 9.3?±?1.4?Bq/l in well water, respectively, and minimum were found 17.1?±?3.6 mBq/l and 1.6?±?1.0?Bq/l in tap water, respectively. A positive correlation (R=.88) was found between ²²⁶Ra and ²²²Rn determined by HPGe and RAD7 detectors, respectively. Infants in the age group of 0–1 y appeared to be at risk with respect to the annual effective doses from ²²⁶Ra and ²²²Rn as compared to the other age groups. However, annual effective doses for all three age groups from intake of ²²⁶Ra and ²²²Rn in well and tap drinking water were found below the World Health Organization (WHO) recommended level of .1 mSv/y_.     

Long-term variation of outdoor radon equilibrium equivalent concentration

Long-term variation of outdoor radon equilibrium equivalent concentration was investigated from 1982 to 1992 at a semi-natural location 10 km north of Munich, southern Germany. For this period the continuous measurement yielded a long-term average of 8.6 Bq·m^–3 (arithmetic mean) and 6.9 Bq·m^–3 (geometric mean), from which an average annual effective dose of 0.14 mSv due to outdoor radon can be derived. A long-term trend of the radon concentration was not detectable over the whole period of observation. However, by time series analysis, a long-term cyclic pattern was identified with two maxima (1984–1986, 1989–1991) and two minima (1982–1983, 1987–1988). The seasonal pattern is characterized by an autumn maximum and an early summer minimum. On average, the seasonal maximum in October was found to be higher by a factor of 2 than the June minimum. The diurnal variation of the radon concentration shows a maximum in the early morning and a minimum in the afternoon. On average, this maximum is a factor of 2 higher than the minimum. In the long term a seasonal pattern was observed for diurnal variation, with an average diurnal maximum to minimum ratio of 1.5 in winter compared with 3.5 in the summer months. The radon concentration is correlated with a meteorological parameter (stagnation index) which takes into account horizontal and vertical exchange processes and the wash-out of aerosols in the lower atmosphere.Dedicated to Prof. F. Waschsmann on the occasion of this 90th birthday     

Estimation of dose rate for indoor radon from building materials

The internal dose rate due to indoor radon (Rn) emissions from building materials is estimated. It is observed that the contribution from building materials to the dose rate is very small. The average indoor radon concentration in 75 different rooms is found to be 55 ± 12 Bq. m^–3. Assuming an occupancy factor of 0.8, the annual average effective dose equivalent is 1.7 mSv. It seems that soil gas is mainly responsible for the internal exposure from indoor Rn.     

Dynamics of production oftrans-zeatin andtrans-zeatin riboside by immobilized cytokinin-autonomous and cytokinin-dependent tobacco cells

Two strains of cultured tobacco cells (Nicotiana tabacum L. cv. Wisconsin 38) differing in their requirement for exogenous cytokinins (cytokinin-dependent and cytokinin-autonomous) were immobilized on polyphenylenoxide (Sorfix) activated with glutaraldehyde. Columns packed with immobilized cells were continually eluted with diluted Murashige and Skoog's medium lacking or supplemented with synthetic cytokinin (6-benzylaminopurine; BA). Purified samples of column eluates were fractionated by HPLC, andtrans-zeatin (t-Z) andtrans-zeatin riboside (t-ZR) content was estimated by enzyme immunoassay. Both cytokinin-autonomous and cytokinin-dependent tobacco cells produced and excretedt-Z and its riboside, and there were significant quantitative differences between the strains. The steady-state excretion rate oft-Z was 19.8 ng · g^–1 dw · h^–1 and 4 ng · g^–1 dw · h^–1, respectively, and that oft-ZR 4 ng · g^–1 dw · h^–1 and 1 ng · g^–1 dw · h^–1, respectively. Exposure of cytokinin-dependent cells to BA after 72 h of starving for this synthetic cytokinin caused temporary increase in excretion of both zeatin and its riboside. After the application of 5 M BA for 24 h, the excretion rate oft-ZR reached 5 ng · g^–1 dw · h^–1 (5-fold increase), and that oft-Z achieved 12 ng · g^–1 dw · h^–1 (3-fold increase). The elevation oft-Z excretion was delayed about 13 h compared witht-ZR excretion, which started increasing almost immediately after BA application. A pulse of BA in lower concentration (1.5 M for 30 h) provoked lower response.     

Comparative study of 222Rn/220Rn progeny concentration and estimation of age-dependent dose due to inhalation of radon progeny for different body organs

In the present study, the age-dependent doses due to inhalation of short lived decay progeny of radon, i.e., ²¹⁴Po to different body organs have been calculated for the inhabitants of the Jammu district, Jammu &; Kashmir, India. The estimated age-dependent doses for different body organs due to inhalation of radon progeny through air for all age groups varied between 0.002E-06 and 0.10 n Svy^?1 which were found to be well within the recommended limit of 1000 µ Svy^?1 (ICRP). The progeny concentration of radon and thoron was calculated and compared by two different techniques. The attached and un-attached progeny concentration of radon and thoron was calculated by using a passive time integrating, deposition-based technique. The measured attached and un-attached radon and thoron progeny concentrations have been cross-checked by on-line active technique, i.e., Flow-mode Integrated Sampler. A weak positive correlation has been observed between the two devices. The median value of un-attached fraction was found to be 0.15 and 0.12 for thoron and radon progeny, respectively and found to have a log-normal distribution. A good positive correlation has been observed between radon and thoron progeny concentrations.     

Cancer Mortality Studies in Misara,a Radon Hot Spring in Japan: A Summary up to 2003

Misasa, which is well known for its radon hot springs, is a historical town located in Tottori Prefecture, Japan. The presence of the hot springs is noted in an 1164 entry in town records. The presence of radioactivity in the hot springs was recognized in 1914. Since ancient times, the spring water has been believed to be healthful. The town of Misasa has 90 radon hot spring sources, yielding a total volume of 3,000 tons of spring water a day. The concentration of ²²²Rn in the spring water ranges from 17.4 to 9,361 Bq per liter. A series of cancer mortality studies on the radon hot springs were conducted through the collaboration of scientists scattered throughout different Japanese cities. At present, no definite evidence has been discovered that indicates an increase of cancer mortality in the Misasa radon hot spring area. Even a lower risk was found for stomach cancers in both radon and no-radon hot springs.     

Occurrence of radon in some schools of Parma and Reggio Emilia (Northern Italy)

Summary Forty-seven measurement of radon concentration were made in some schools of Parma, Reggio Emilia, Albinea and Borzano. The method used was that of activated carbon canisters, which were placed in classrooms, laboratories, libraries and headmaster's offices for at least 48 hours in the period November '90–March '91. It was possible to determine the amount of radon in each canister counting the Pb-214 and Bi-214 gamma emitters by means of NaI (Tl) and Ge (I) detectors. The mean radon concentrations were: 20 Bq/m³ in Parma; 24 Bq/m³ in Reggio Emilia; 46 Bq/m³ in Borzano and 52 Bq/m³ in Albinea. The values recorded in schools are similar to the values previously recorded in dwellings of Parma and Reggio Emilia.     

Digestion and energy metabolism in a small arboreal marsupial,the Greater Glider (Petauroides volans), fed high-terpeneEucalyptus foliage

Summary The digestion and metabolism ofEucalyptus radiata foliage was studied in a small (1–1.5 kg) arboreal marsupial, the greater glider (Petauroides volans). Mean dry matter intake was 44 g·kg^–0.75·d^–1 and mean cell wall digestibility was 34%; these values fall within the range of other marsupials fedEucalyptus foliage. Digestible energy content ofE. radiata was high compared to other eucalypts because of the high content and digestibility of essential oils. However, excretion of essential oils and their metabolites in the urine meant that greater gliders retained only 55% of their digestible energy intakes (0.61 MJ · kg^–0.75· d^–1) as metabolizable energy (ME). Low ME intakes were not offset by low standard metabolic rates (2.39 W · kg^–0.75), but the efficiency with which ME substituted for tissue energy was high (94%), so that greater gliders were able to maintain energy balance and body mass onE. radiata foliage.Abbreviations ME metabolizable energy - DE digestible energy - RQ respiratory quotient - FHP fasting heat production     

Estimates of microcurie-days residence,bone dose equivalent,and (MPC)W for thorium-232 in man using a mammillary model

A four-compartment mammillary model for the distribution and excretion of thorium and its daughter radium is studied and applied to the problem of estimating the radiation dose to organs and tissues of man for the case of a single intake of²³²Th. The long-lived daughter²²⁸Ra (∼6 y) grows in with time and gives birth to the other short-lived daughters (<0.4 day) which irradiate those tissues in the vicinity of their point of production. Some data on²²⁸Th and its daughter²²⁴Ra are available on dogs from which a model is derived and tested. Then, from some single-intake data (Th and Ra) on man, parameters for the model are estimated and estimates of residence times of the²³²Th daughters in man are made. Also, the 50-year radiation dose (dose equivalent) to bone from a single intake of²³²Th is estimated. Research sponsored by the U.S. Atomic Energy Commission under contract with Union Carbide Corporation.     

Is Radon Emission in Caves Causing Deletions in Satellite DNA Sequences of Cave-Dwelling Crickets?

The most stable isotope of radon, ²²²Rn, represents the major source of natural radioactivity in confined environments such as mines, caves and houses. In this study, we explored the possible radon-related effects on the genome of Dolichopoda cave crickets (Orthoptera, Rhaphidophoridae) sampled in caves with different concentrations of radon. We analyzed specimens from ten populations belonging to two genetically closely related species, D. geniculata and D. laetitiae, and explored the possible association between the radioactivity dose and the level of genetic polymorphism in a specific family of satellite DNA (pDo500 satDNA). Radon concentration in the analyzed caves ranged from 221 to 26000 Bq/m³. Specimens coming from caves with the highest radon concentration showed also the highest variability estimates in both species, and the increased sequence heterogeneity at pDo500 satDNA level can be explained as an effect of the mutation pressure induced by radon in cave. We discovered a specific category of nuclear DNA, the highly repetitive satellite DNA, where the effects of the exposure at high levels of radon-related ionizing radiation are detectable, suggesting that the satDNA sequences might be a valuable tool to disclose harmful effects also in other organisms exposed to high levels of radon concentration.     

Pulmonary diffusing capacity in reptiles (Relations to temperature and O2-uptake)

Summary Pulmonary CO-diffusing capacity (D l _CO), lung volume, pulmonary perfusion and O₂-uptake were measured by non-invasive techniques in the lizardsVaranus exanthematicus andTupinambis teguixin (mean body weight 2.2 kg for both species).The CO-diffusing capacity was at 25–27°C 0.059 mlstpd·kg^–1·min^–1·Torr^–1 inVaranus, which is 47% greater than the value of 0.040 mlstpd·kg^–1·min^–1·Torr^–1 inTupinambis. The lung volume ofVaranus was 36 ml·kg^–1 and that ofTupinambis 20 ml·kg^–1. At 35–37°C the diffusing capacity of lizard lungs are about 25% of those for mammals of comparable size.InVaranus pulmonary CO-diffusing capacity increased with temperature from 0.027 mlstpd·kg^–1·min^–1·Torr^–1 at 17–19 °C to 0.075 mlstpd·kg^–1·min^–1·Torr^–1 at 35–37 °C. This change closely matched a concomitant increase of O₂-uptake. Pulmonary perfusion increased from 27 ml·kg^–1·min^–1 to 55 ml·kg^–1·min^–1 within this temperature range.The study emphasizes that pulmonary diffusing capacity cannot be fully evaluated without information on pulmonary perfusion and O₂-uptake. In reptiles and other ectotherms diffusing capacity must be reported at specified body temperature.