Radon transfer from thermal water to human organs in radon therapy: exhalation measurements and model simulations.

The transfer of radon from thermal water via the skin to different human organs in radon therapy can experimentally be determined by measuring the radon activity concentration in the exhaled air. In this study, six volunteers were exposed to radon-rich thermal water in a bathtub, comprising eleven measurements. Exhaled activity concentrations were measured intermittently during the 20 min bathing and 20 min resting phases. Upon entering the bathtub, the radon activity concentration in the exhaled breath increased almost linearly with time, reaching its maximum value at the end of the exposure, and then decreased exponentially with time in the subsequent resting phase. Although for all individuals the time-dependence of exhaled radon activity was similar during bathing and resting, significant inter-subject variations could be observed, which may be attributed to individual respiratory parameters and body characteristics. The simulation of the transport of radon through the skin, its distribution among the organs, and the subsequent exhalation via the lungs were based on the biokinetic model of Leggett and co-workers, extended by a skin and a subcutaneous fat compartment. The coupled linear differential equations describing the radon activity concentrations in different organs as a function of time were solved numerically with the program package Mathcad. An agreement between model simulations and experimental results could only be achieved by expressing the skin permeability coefficient and the arterial blood flow rates as a function of the water temperature and the swelling of the skin.

Cryoconites from Alpine glaciers: Radionuclide accumulation and age estimation with Pu and Cs isotopes and 210Pb.

Cryoconites ("cold dust", derived from the Greek) are aeolian sediments accumulated on glacier surfaces. In cryoconites from the surface of the Stubacher Sonnblickkees, a temperate Austrian glacier, extremely high activity concentrations of artificial and natural radionuclides were found. Artificial radionuclides stem from two clearly distinguishable sources, global fallout from the nuclear weapons testing era deposited over a period of years until roughly 1966 and the fallout from Chernobyl in 1986, which was essentially deposited as a single input during one week. Anthropogenic radionuclides identified were 137Cs, 134Cs, 238Pu, 239+240Pu, 90Sr, 241Am, 60Co, 125Sb, 154Eu, and 207Bi. The naturally occurring radionuclides detected were the long-lived radon decay product 210Pb, the primordial radionuclide 4 K and the cosmogenic 7Be. Isotopic ratios of 134Cs/137Cs and 239+240Pu/238Pu were used to separate the nuclide inventory into the contributions of the two aforementioned sources, which show varying degrees of mixing and provide information on the mixing age of the cryoconites. Since isotopic ratios of Pu often have high uncertainties due to low absolute concentrations, age estimation based on this method can be quite inaccurate. Additional information about the age of cryoconites was obtained through analysis of 210Pb, which is constantly deposited over time.

Accumulation of anthropogenic radionuclides in cryoconites on Alpine glaciers.

Cryoconites are airborne sediments which accumulate on the surface of glaciers. In samples of cryoconites a temperate Austrian glacier high activity concentrations of anthropogenic radionuclides were found, which stem from global and Chernobyl fallouts. Radionuclides identified were (137)Cs, (134)Cs, (238)Pu, (239+240)Pu, (90)Sr, (241)Am, (60)Co, (154)Eu, (207)Bi, and (125)Sb. Given the approximately known isotopic ratios, Cs and Pu can be separated into the contributions of either source of origin. Published (137)Cs/(134)Cs and (239+240)Pu/(238)Pu ratios were used for the discrimination of the Dachstein-glacier cryoconites according to their origin from global or Chernobyl fallout. Two different groups of cryoconites were identified, an older population dominated by nuclear weapons fallout and a younger one with predominant Chernobyl fallout. With those data a simple model was formulated to demonstrate the transition and mixing of these two populations on the glacier surface.

Determination of (137)Cs in the water system of a pre-Alpine lake.

The aim of this study was to measure the (137)Cs activity derived from the Chernobyl accident in the water system of Lake Wallersee, a pre-Alpine lake in Austria within an area highly contaminated by the Chernobyl fallout. For this purpose, water and sediment samples of the inflows and the outflow of Lake Wallersee and lake water at different depths were collected in 2005. The obtained (137)Cs activity depth profile in the water body shows an exponential increase of (137)Cs activity in the lake water with increasing depth. Inflow and outflow sediment analyses exhibit a clear negative correlation between particle size and specific activity for (137)Cs and (40)K in sediment samples following a power function. In a first approach it was tried to calculate the catchment run-off factor of (137)Cs during a period without heavy rainfalls. The result is in good agreement with run-off factors determined in other similar investigations in Austria.

Determining the Chernobyl impact on sediments of a pre-Alpine lake with a very comprehensive set of data.

Man-made and natural radionuclides in Lake Wallersee were determined in the pre-Alpine environment at the northern slope of the Alps, which was heavily affected by the Chernobyl fallout in May 1986. The objective of this study was to get knowledge of location and quantity of man-made radionuclide input (especially (137)Cs) generated in the Chernobyl accident to lake sediments. Eleven sediment cores were sampled and activity depth profiles of (137)Cs and (210)Pb were determined with 5mm depth-resolution. The Chernobyl fallout produced an extreme (137)Cs peak in the sediment cores providing an excellent time marker. The chronological interpretation of deeper sediment layers was done by radiochemical analysis of (90)Sr and (239+240)Pu, which were released during atmospheric weapons' tests in the 1950s and 1960s. This allowed a complete chronological analysis of the sediment cores with a very compact set of data.

137Cs and 90Sr transfer to milk in Austrian alpine agriculture.

The alpine regions of Austria were among the most contaminated territories outside of the former USSR after the Chernobyl accident. In the investigated province of Salzburg the median (137)Cs surface deposition was 31.4 kBq m(-2) with maximum values exceeding 90 kBq m(-2) (May 1986). To quantify the transfer of (137)Cs and (90)Sr from vegetation to milk in these seminatural conditions nine seasonally grazed alps were identified and vegetation and milk sampled during summer 2002 and summer 2003. Mean+/-SD milk transfer coefficients (fm) for (137)Cs and (90)Sr were 0.0071+/-0.0009 d l(-1), and 0.0011+/-0.0004 d l(-1), respectively; which for (137)Cs is markedly higher than those fm values found in intensive agricultural systems. Transfer kinetics for (137)Cs into cow milk were approximated using a 2-compartment model with a short and a long-term component. Fitting the model to empirical data results in reliable estimates of the time constant of the short-term component, biological half-life 1.06+/-0.28 d, whereas the estimates of the long-term component are subject to high uncertainties.

Activity ratios of 137Cs, 90Sr and 239+240Pu in environmental samples.

Both global and Chernobyl fallout have resulted in environmental contamination with radionuclides such as 137Cs, 90Sr and 239+240Pu. In environmental samples, 137Cs and 239+240Pu can be divided into the contributions of either source, if also the isotopes 134Cs and 238Pu are measurable, based on the known isotopic ratios in global and Chernobyl fallout. No analogous method is available for 90Sr. The activity ratios of Sr to Cs and Pu, respectively, are known for the actual fallout mainly from air filter measurements; but due to the high mobility of Sr in the environment, compared to Cs and Pu, these ratios generally do not hold for the inventory many years after deposition. In this paper we suggest a method to identify the mean contributions of global and Chernobyl fallout to total Sr in soil, sediment and cryoconite samples from Alpine and pre-Alpine regions of Austria, based on a statistical evaluation of Sr/Cs/Pu radionuclide activity ratios. Results are given for Sr:Cs, Sr:Pu and Cs:Pu ratios. Comparison with fallout data shows a strong depletion of Sr against Cs and Pu.

A note on 207Bi in environmental samples.

Traces of the radionuclide (207)Bi were identified in soil and cryoconite (glacier sediment) samples from Alpine regions of Austria. This nuclide has been produced in thermonuclear explosions mainly in the early 1960s and subsequently dispersed in the atmosphere. Activity concentrations up to 22 Bq/kg d.m. have been found. The ratio (207)Bi:(137)Cs(global fallout) equals (1.70+/-0.12)10(-3), which is in accordance with literature data. When low levels of (207)Bi are assessed by gamma spectrometry, corrections must be made for a gamma line produced in the lead shield by neutron activation due to cosmic neutrons.

Radiocaesium in flowing waters of highly contaminated Austrian alpine areas.

In this study the runoff of (137)Cs, mainly originated from the Chernobyl fallout, from highly contaminated alpine regions in Salzburg (Austria) is discussed. Twenty-five water-samples and 25 sediment-samples were taken from creeks of different size to determine the runoff of dissolved (137)Cs and Cs-binding characteristics to different particle size classes in the sediments. The hypothesis, that specific activity of the sediments depended on particle size and the surface of the particle, was proved with some modifications. Caesium activity concentration in water showed a negative correlation with electrical conductivity, while no significant correlations were detectable with other variables (pH, temperature, and altitude). Enormous differences and the variations found in the (137)Cs-concentrations in water can be explained by the electrical conductivity without any dependency on the inventory of the catchment. The sediment samples analysed showed a negative correlation between specific activity [Bq/kg] and particle-diameter, mainly explained by (137)Cs-uptake proportional to the particle surface per mass.

Cytogenetic biomonitoring carried out in a village (Dolon) adjacent to the Semipalatinsk nuclear weapon test site.

The Semipalatinsk region (Kazakhstan Republic) has been affected by extensive radioactive contamination due to more than 450 nuclear tests of which almost 100 were exploded in the atmosphere. The present results refer to cytogenetic assessments in a study cohort of the population of Dolon, a settlement located on the NE boundary of the nuclear weapon test site, which was exposed to elevated doses of ionising radiation primarily due to the first Soviet nuclear test in 1949. Conventional cytogenetic analyses were carried out on 21 blood samples from individuals (more than 50 years old) living in Dolon since the very beginning of nuclear testing. A matched control group included 20 individuals living in non-contaminated areas. Higher frequencies of chromosome aberrations were found in the Dolon cohort compared to the control group, even though they remain within the range of the background levels reported for large normal human population studies on elderly individuals.

Fallout strontium and caesium transfer from vegetation to cow milk at two lowland and two Alpine pastures.

Vegetation-to-milk transfer coefficients for 137Cs, 90Sr and stable strontium were determined for cows grazing on two intensively managed lowland pastures and two Alpine pastures in Austria. The 90Sr transfer coefficient at the four pastures ranged from 0.0005 to 0.0012 dl-1 and correlated with the stable strontium transfer coefficient (0.0006-0.0013 dl-1) with the lower values found on the intensively managed pastures. The 137Cs transfer coefficient ranged from 0.0009-0.0045 dl-1.

90Sr and 137Cs in environmental samples from Dolon near the Semipalatinsk Nuclear Test Site.

The (90)Sr and (137)Cs activities of soil, plant, and milk samples from the village of Dolon, located close to the Semipalatinsk Nuclear Test Site in Kazakhstan, were determined. The areal deposition at the nine sampling sites is in the range of <500 to 6,100 Bq m(-2) and 300 to 7,900 Bq m-2 for (90)Sr and (137)Cs, respectively. Similar values have been reported in the literature. At some of the sites both nuclides mainly have remained in the top 6 cm of the soil profiles; at others they were partly transported into deeper soil layers since the deposition. For most of the samples the (90)Sr yield after destruction of the soil matrix is significantly higher than after extracting with 6 M HCl indicating that (90)Sr is partly associated with fused silicates. The low mean (90)Sr activity concentrations of vegetation samples (14 Bq kg(-1) dw) and milk samples (0.05 Bq kg(-1) fw) suggest that this has favorable consequences in terms of limiting its bioavailability.

Role of calcium in photodynamically induced cell damage of human fibroblasts.

Photodynamically induced changes in the cytoplasmic free calcium concentration ([Ca2+]i) and its role in cell damage were investigated in human skin fibroblasts using confocal laser microscopy. Fluorescence and absorbance spectrophotometry measurements indicate that the photosensitizer aluminum phthalocyanine tetrasulfonate (AIPcS4) binds to the plasma membrane and only after irradiation is able to enter the cells, causing massive morphologic alterations. Upon irradiation of sensitizer-treated cells, the increase in [Ca2+]i is related to the amount of light and extracellular [Ca2+]e. The increase in [Ca2+]i was substantially reduced in the absence of [Ca2+]a. Cell damage or death after photodynamic treatment was prevented and shifted toward higher fluence by increasing [Ca2+]i at high [Ca2+]e and was greater at low [Ca2+]e. Application of Ca2+ channel blockers, such as Co2+, Cd2+ or verapamil, could not prevent the increase of [Ca2+]i. Our results indicate that activation of the photosensitizer, AIPcS4, causes an influx of Ca2+, which protects cells from, photodamage. At low [Ca2+]e and high fluence values, release of Ca2+ from internal stores probably as a protective measure occurs in order to increase the [Ca2+]i.

Photodynamic effects on the nuclear envelope of human skin fibroblasts.

Photodynamic effects on the nuclear envelope of human skin fibroblasts were investigated by confocal laser fluorescence microscopy and transmembrane resting potential measurements. The results show staining of the nuclear envelope after short incubation times with Photosan III, Photofrin II and haematoporphyrin derivative (HPD) enriched with monomers. Maximum staining was found at the centre of the nuclear envelope. The sequence of fluorescence intensity was HPD enriched with monomers > Photofrin II > Photosan III. After lethal treatment with Photosan III and tetrasulphonated aluminium chloride phthalocyanine, the nuclear transmembrane potential of the nuclear membrane decreased from -20 mV to about -10 mV with reference to the plasma membrane potential.