Constantin Cosma

Comparative risk assessment of residential radon exposures in two radon-prone areas, Ştei (Romania) and Torrelodones (Spain)

Radon and radon progeny are present indoors, in houses and others dwellings, representing the most important contribution to dose from natural sources of radiation. Most studies have demonstrated an increased risk of lung cancer at high concentration of radon for both smokers and nonsmokers. The work presents a comparative analysis of the radon exposure data in the two radon-prone areas, Stei, Transylvania, (Romania), in the near of old Romanian uranium mines and in the granitic area of Torrelodones town, Sierra de Guadarrama (Spain). Measurements of indoor radon were performed in 280 dwellings (Romania) and 91 dwellings (Spain) by using nuclear track detectors, CR 39. The highest value measured in Stei area was 2650 Bq m(-3) and 366 Bq m(-3) in the Spanish region. The results are computed with the BEIR VI report estimates using the age-duration model at an exposure rate below 2650 Bq m(-3). We used the EC Radon Software to calculate the lifetime lung cancer death risks for individuals groups in function of attained age, radon exposures and tobacco consumption. A total of 233 lung cancer deaths were observed in the Stei area for a period of 13 years (1994-2006), which is 116.82% higher than expected from the national statistics. In addition, the number of deaths estimated for the year 2005 is 28, which is worth more than 2.21 times the amount expected by authorities. In comparison, for Torrelodones was rated a number of 276 deaths caused by lung cancer for a period of 13 years, which is 2.09 times higher than the number expected by authorities. For the year 2005 in the Spanish region were reported 32 deaths caused by pulmonary cancer, the number of deaths exceeding seen again with a factor of 2.10 statistical expectations. This represents a significantly evidence that elevated risk can strongly be associated with cumulated radon exposure.

Recent changes in Red Lake (Romania) sedimentation rate determined from depth profiles of 210Pb and 137Cs radioisotopes

This work presents a first estimation of the sedimentation rate for the Red Lake (Romania). The sediment accumulation rates were determined by two well-known methods for recent sediment dating: (210)Pb and (137)Cs methods. Both techniques implied used the gamma emission of the above-mentioned radionuclides. The (210)Pb and (137)Cs concentrations in the sediment were measured using a gamma spectrometer with a HpGe detector, Gamma-X type. Activities ranging from 41+/-7 to 135+/-34Bq/kg were found for (210)Pb and from 3+/-0.5 to 1054+/-150Bq/kg for (137)Cs. The sediment profile indicates acceleration in sedimentation rate in the last 18 years. Thus, the sedimentation process for the Red Lake can be divided in two periods, the last 18 years, and respectively, the period before that. Using the Constant Rate of (210)Pb Supply method values between 0.18+/-0.04 and 1.85+/-0.5g/cm(2) year (0.32+/-0.08 and 2.83+/-0.7cm/year) were obtained. Considering both periods, an average sedimentation rate of 0.87+/-0.17g/cm(2) year (1.17cm/year) was calculated. Considering an average depth of 5.41m for the lake and the sedimentation rate estimated for the last 18 years, it could be estimated that the lake will disappear in 195 years.

Soil and building material as main sources of indoor radon in Băiţa-Ştei radon prone area (Romania).

Radon contributes to over than 50% of the natural radiation dose received by people. In radon risk areas this contribution can be as high as 90-95%, leading to an exposure to natural radiation 5-10 times higher than normal. This work presents results from radon measurements (indoor, soil and exhalation from building materials) in Băiţa-Ştei, a former uranium exploitation area in NW Romania. In this region, indoor radon concentrations found were as high as 5000 Bq m(-3) and soil radon levels ranged from 20 to 500 kBq m(-3). An important contribution from building materials to indoor radon was also observed. Our results indicate two independent sources of indoor radon in the surveyed houses of this region. One source is coming from the soil and regular building materials, and the second source being uranium waste and local radium reached material used in building construction. The soil as source of indoor radon shows high radon potential in 80% of the investigated area. Some local building materials reveal high radon exhalation rate (up to 80 mBq kg(-1) h(-1) from a sandy-gravel material, ten times higher than normal material). These measurements were used for the radon risk classification of this area by combining the radon potential of the soil with the additional component from building materials. Our results indicate that Băiţa-Ştei area can be categorized as a radon prone area.

Thorough investigations on indoor radon in Băiţa radon-prone area (Romania).

A comprehensive radon survey has been carried out in Băiţa radon-prone area, Transylvania, Romania, in 4 localities (Băiţa, Nucet, Fînaţe, and Cîmpani) situated in the vicinity of former Romanian uranium mines. Indoor radon concentrations have been measured in 1128 ground floor rooms and cellars of 303 family houses by using CR-39 diffusion type radon detectors. The annual average of indoor radon concentration for Băiţa area was found to be 241±178 Bq m(-3), which is about two times higher than the average value of 126 Bq m(-3), computed for Romania. About 28% of investigated houses exceed the reference level of radon gas in dwellings of 300 Bq m(-3). The indoor radon measurements on each house have been carried out in several rooms simultaneously with the aim of obtaining a more detailed picture on the exposure to radon in the studied area. An analysis on the variability of radon levels among floors (floor-to-floor variation) and rooms (room-to-room variation) and also the influence of factors like the presence of cellar or the age of the building is presented. The coefficient of variation (CV) within ground floor rooms of the same house (room-to-room variation) ranged between 0.9 and 120.8%, with an arithmetic mean of 46.2%, a large variability among rooms within surveyed dwellings being clearly identified. The mean radon concentration in bedrooms without cellar was higher than in bedrooms above the cellar, the difference being statistically significant (t test, one tail, p<0.001, n=82). For houses built during 1960-1970 an increasing trend for radon levels was observed, but overall there was no significant difference in indoor radon concentrations by age of dwelling (one-way ANOVA test, p>0.05).

A high resolution optical dating study of the Mostiştea loess-palaeosol sequence (SE Romania) using sand-sized quartz

We report on SAR-OSL dating of closely-spaced samples from the loess-palaeosol sequence near Mostiştea lake (Danube Plain, SE Romania). We used sand-sized quartz and a SAR protocol that involved a preheat of 10s at 220°C and a test dose cutheat to 180°C. It is shown that these thermal pretreatments isolate a quartz OSL signal that is dominated by the fast component. The behaviour of this signal in the SAR protocol is then documented. The ratio of the measured to given dose tends to lie slightly but systematically above unity (∼5% on average) and the recycling ratio below unity (∼6% on average); for all samples, the recuperated signal is negligible. Within analytical uncertainty, the nineteen optical ages are internally consistent and agree with the predictions from a palaeomagnetic age-depth model. Although it may be possible to optimize the SAR measurement procedure, the optical ages already confirm the chronostratigraphic position of the uppermost welldeveloped palaeosol in that it formed during MIS 5. The established chronology allows correlating the sequence near Mostiştea lake with that near Mircea VodĂ that we investigated earlier.

Preliminary integrated indoor radon measurements in Transylvania (Romania).

Measurements of indoor radon concentrations were performed in 406 residential houses in five counties (Cluj, Bihor, Alba, Bistrita, and Sibiu) using Makrofol and CR-39 alpha-track detectors. From our measurements, an average indoor radon concentration of 82.5 Bq m−3 for the Transylvanian population was calculated, i.e. an annual effective dose of 2.4 mSv for the whole body. The calculated dose is 62% higher than that previously reported but yet below the recommended action level of ICRP (International Commission on Radiological Protection). A log-normal distribution of the radon concentration was obtained for the studied counties, excluding some higher values from the Stei region – a radon-prone area in Transylvania. For the Stei region, the data show a dual log-normal distribution of the radon concentration with the second maximum being related to the houses built using uranium waste as a construction material. Assuming a cancer risk coefficient of 10−4/100 Bq m−3 year−1, one can estimate that about 600 lung cancer per year, for about 7,000,000 inhabitants of the Transylvania region, are due to radon inhalation.

Luminescence dating of neolithic ceramics from Lumea Nouă, Romania

Luminescence Dating of Neolithic Ceramics from Lumea Nouă, Romania Luminescence dating was applied to four Neolithic pottery fragments excavated at Lumea Nouă (Alba Iulia, Romania), with the purpose of improving the chronology for the archaeological finds, and hence, the occupational history of the site. The single-aliquot regenerative-dose (SAR) protocol was applied to both blue and infrared stimulated luminescence signals from coarse quartz and polymineral fine grains, respectively. A more conventional approach which uses a multiple-aliquot additive-dose protocol and thermoluminescence signals from polymineral fine grains was applied as well. The characteristics of the OSL and IRSL signals were investigated in terms of behaviour in the SAR protocol, dose response and dose recovery. Additionally, anomalous fading measurements of the 410 nm IRSL emission and of the blue TL emission from polymineral fine-grains were performed. Both signals were observed to be affected by anomalous fading. OSL dating of quartz using the SAR protocol is considered to be the technique of choice; it yields an average age of 6.0±0.4 ka (n = 4), which is in agreement with archaeological expectations. The dating results allow refining the typological interpretation of the objects and improve the chronological framework for the site.

A sedimentation study of St. Ana Lake (Romania) applying the 210Pb and 137Cs dating methods

The biggest problem with most lakes that have no contact with other water sources and are being charged by precipitation is the massive eutrophication. The aim of this work was to determine the sedimentation rate in order to evaluate the progress of eutrophication for St. Ana Lake (Ciomad Mountain near the Băile Tuşnad in Harghita County (Romania)). The concentration of 210Pb was determined by means of high resolution gamma spectrometry as well as derived from 210Po activity which was measured through alpha spectrometry; values obtained are in good agreement. For the excess 210Pb activity values between 4.0±0.5 Bq/kg and 218±20 Bq/kg have been found. As an alternative method, the 137Cs dating method was applied as well. Calculated mass sedimentation rates are in the range of 0.06±0.01 to 0.32±0.05 g/cm2 year with a mean of value of 0.15±0.02 g/cm2 year. Linear sedimentation rates yielded much higher sedimentation values (between 0.5±0.1 and 7.9±0.7 cm/year with a mean of 2.4±0.6 cm/year), due to the predominant organic matter composition and the long suspension time of the sediment. This is an indication for the process of eutrophication which will probably lead to the transformation of the lake into a peat bog.

Preliminary lung cancer risk assessment of exposure to radon progeny for Transylvania, Romania.

The objective of the present study was to assess the lung cancer risk induced by exposures to radon progeny of people living in some areas of Transylvania, Romania. Indoor radon concentrations were measured in 667 dwellings of Stei area, Cluj, Bistrita-Nasaud, Sibiu, and Alba counties. Measurements were performed using CR-39 track detectors, exposed for a minimum of 3 mo. Average annual radon concentrations were 232, 114, 71, 62, and 161 Bq m−3 for Stei area, Cluj, Bistrita-Nasaud, Sibiu, and Alba, respectively. The linear risk model of Darby was used to simulate the dose-effect relationship and relative lung cancer risk at low doses of alpha particles specific to residential radon exposures. Predicted relative risks at the measured exposure levels, together with information on the total number of reported lung cancer deaths and the number of people living in these regions, enabled us to estimate the fraction of lung cancer cases in each area that is attributable to radon. These percentages are 16.67% for Stei area, 9.09% for Cluj, 5.66% for Bistrita-Nasaud, 4.76% for Sibiu, and 12.28% for Alba county among lifetime non-smokers. Assuming that the smoking rates are similar for the investigated regions (10.72% smokers among men and 5.95% among women), around 64 to 69% of the total number of annual lung cancer deaths, stratified by sex, would be attributed to radon and occur among smoking male population, and around 35 to 44% would be attributed to radon and occur among smoking female population.

Radon survey in caves from Mallorca Island, Spain.

This study reports radon concentration in the most representative caves of Mallorca, identifying those in which the recommended action level is exceeded, thus posing health risks. Two show caves (Campanet and Artà) and three non-touristic caves (Font, Drac, Vallgornera) were investigated. Data were collected at several locations within each cave for three different periods, from March 2013 to March 2014. Except for Vallgornera, where only one monitoring period was possible, and Artà in which low values were recorded throughout the year, a clear seasonal variability, with higher values during the warm seasons and lower during winter time is prominent. Radon concentrations differed markedly from one cave to another, as well as within the same cave, ranging from below detection limit up to 3060 Bq·m(-3). The results of this study have significant practical implications, making it possible to provide some recommendation to cave administrators and other agencies involved in granting access to the investigated caves.