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.

Radon risk management: the future challenge for the nuclear community.

The short-lived decay products (Rn-d) of radon gas (222Rn, 220Rn) have been identified as a health hazard in occupational exposure situations, as well as a public health risk in general. Decisions will have to be made concerning the initiation and scale of national Rn-mitigation programmes. In view of the potentially significant socio-economic impact of such programmes, it is recommended to proceed from the current approach based on Rn-d risk assessment to the integrated approach of radon risk management (RRM). A seven-step RRM is proposed, ranging from the selection of an action level based on an incremental risk-reduction, to the conduct of auditing procedures, monitoring the RRM-outreach factor.

Results and conclusions of the Austrian radon mitigation project 'SARAH'.

The Austrian radon mitigation joint research project SARAH (supported by the Austrian Ministry of Economy and the Government of Upper Austria), a 2-year follow-up study of the Austrian National Radon Project (ONRAP), was started in 1996. The objectives of the research project were to find simple, cost-effective experimental methods for the characterisation of the radon situation in dwellings and to evaluate technically and economically the implementation of state of the art remedial actions for Austrian house types. After an intercomparison exercise of the assigned radon measuring instruments and detectors five houses were closely examined in regions with elevated radon levels in the federal state of Upper Austria. In this research work for the first time an extended Blower-Door method (which is conventionally used for determining the tightness of buildings) was successfully applied to radon diagnosis of buildings. In this paper the methods used for the radon diagnosis, the applied mitigation measures and the related technical and economical aspects are discussed. In conclusion of the results of this project a common strategy for solving the radon problem in Austria in the future is presented briefly.

Elevated indoor exposure in Chinese carbon brick and cave dwellings.

In two rural provinces of China residents are exposed to significantly elevated levels of natural radiation: in Gansu Province millions of people have been living in earth-dug cave dwellings for several generations; in Jiangxi Province several hundred thousand inhabitants reside in carbon-brick dwellings, containing elevated levels of 238U and 226Ra. In a pilot study regional lung cancer mortality rates were investigated in the affected areas and were found to be higher than for control groups in normal dwellings in the same area.

Dose assessment for recent inhabitants living adjacent to zones heavily contaminated from the Chernobyl fallout.

Within the framework of the "International Chernobyl Project," selected areas in the Republics of Ukraine, Belarus, and Russia of the former USSR, contaminated by radioactive fallout from the Chernobyl accident in 1986, were investigated by international teams. In addition, environmental studies were carried out in areas officially declared as "uncontaminated regions" in order to corroborate this classification and to provide reference baseline data for the simultaneously performed medical investigations on health effects in the contaminated areas. Altogether, 141 measurements of the gamma dose rate, both outdoors and indoors, were carried out. Also, the radionuclide concentration in 58 soil and food sample was determined. In addition, results from 1,620 individual film dosimeter readings were analyzed. The results show that, in areas adjacent to those officially designated as contaminated regions (137Cs surface ground contamination > or = 37 kBq m-2), levels of environmental fallout contamination are insignificant. The additional resulting committed effective dose over the next 70 years due to the fallout is only a fraction of the corresponding value from the natural radiation environment.

The main inconsequences in the present radiological protection concept for the general population.

The present concept of radiation protection emphasizes the protection of man against ionizing radiation from manmade sources. But the overwhelming radiation exposure in a given population results from the natural radiation environment (NRE) and the use of radiation in medicine, while less than 2% of the total dose is due to occupational exposure, fallout, releases from nuclear industries, etc. Nevertheless, ICRP recommendations do not apply to, or include, "normal" NRE exposure, nor do they deal with medical exposure of patients by applying risk/benefit considerations. The increasing problems associated with various types of NRE exposures (recycling of waste materials, energy-efficient dwellings) and the continuously increasing use of ionizing radiation in medical practices (x-ray and nuclear diagnostic examinations) require a revision of the present radiation protection concept. In this paper suggestions are made concerning the applicability of a unified concept for controlling all sources of ionizing radiation.

IAEA/EPA international climatic test program for integrating radon detectors. International Atomic Energy Agency/Environmental Protection Agency.

As an element of the joint IAEA-EPA International Radon Metrology Evaluation Program, a climatic test of long-term integrating radon detectors was conducted at the U.S. EPA Radiation and Indoor Environments National Laboratory. The objective of this study was to test the performance of commonly used commercially available long-term 222Rn detector systems under extreme climatological conditions using filtered polycarbonate CR-39 plastic analyzed by the manufacturer using the track-etch method, unfiltered LR-115 film analyzed by the manufacturer, and Teflon based electrets analyzed in the field by EPA using the manufacturer's equipment. The EPA environmental radon chambers were used to expose detectors to extreme cold and dry (less than 4.0 degrees C air temperature and 25% relative humidity) and hot and humid (greater than 35 degrees C air temperature and 85% relative humidity) climatic conditions. During phase I detectors were exposed to low temperatures and low humidities, and during phase II detectors were exposed to high temperatures and high humidities. Typical indoor equilibrium fractions (near 50%) and radon concentrations of about 150 Bq m(-3) were maintained for each phase, which lasted 90 d. The results indicated that the optimal detector for extreme climatic conditions is dependent on the relative importance of bias and precision. Overall, however, the filtered track-etch type detector produced the most reliable results under the extreme conditions.

Radiation exposure of the respiratory tract and associated carcinogenic risk due to inhaled radon daughters.

The atmospheric content of radon and its decay products contributes significantly to the radiation exposure of man even in the normal environment. In this study, the risk for lung cancer induction associated with normal exposure to natural radionuclides is assessed in Salzburg, Austria. Altogether more than a thousand rooms have been investigated by using combined radon grab-sampling methods together with continuous measurements of radon and daughters at different control stations. Dose calculations were carried out for 729 demoscopically selected test persons, considering individual differences in age, sex and life-style and atmospheric nuclide concentrations at different sites. Using a specially developed age-dependent lung model, the dose frequency distribution of the absorbed dose to the basal cells of the bronchial epithelium could be evaluated for the population of Salzburg. Dose modifications caused by anatomical and physiological variabilities as well as microdosimetric considerations of the stochastic events during energy deposition result in a significantly increased dispersion of the dose histogram. Induction of lung cancer due to inhalation of radon and decay products can be correlated with cumulative exposure based on experience with lung cancer incidence amongst uranium miners. Using the recommended range of lifetime risk values of 20-45 X 10(-5)/WLM (UN77), it is shown for Salzburg that about 15% of the observed number of lung cancer cases may be induced by natural radionuclides.

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.

Relationship between the 210Pb content of teeth and exposure to Rn and Rn daughters.

Existing data on 210Pb in human teeth are reviewed for various countries. The mean value of 210Pb in the teeth of population groups exposed to "normal" levels of radon-daughter exposure is about 2 mBq/g. A detailed analysis of 48 samples from a "normal" Italian population group revealed that smoking habits and age may have some influence on 210Pb content of teeth, while this is not the case for differences in sex. A group of 45 Austrians exposed to elevated levels of radon and radon daughters is compared with the Italian group. After subtraction of background levels of 210Pb as found for the normal Italian population, the incremental 210Pb tooth content due to excessive radon-daughter exposure has been correlated with the individual cumulative exposure corrected for background radon-daughter exposure. A statistical analysis shows the significance of the linear correlation at the alpha = 0.01 level. For the incremental increase of 210Pb in teeth, a value of 1.2 mBq/g has been used for a lifetime exposure to 1 WLM. This result is compared to corresponding data published in the literature, which are predominantly related to the 210Pb content of bone after short-time exposure at high levels, e.g. in uranium mines. The comparison seems to indicate the influence of the exposure rate and the need for a comprehensive model, which takes into account radon-daughter inhalation, radon dissolved in body fluids and 210Pb metabolism.

Intercomparison of radon and decay product measurements in an underground mine and EPA Radon Laboratory: a study organized by the IAEA International Radon Metrology Programme. International Atomic Energy Agency.

The International Atomic Energy Agency (IAEA) in Vienna and the European Union (EU) in Bruxelles formed the "International Radon Metrology Programme" (IRMP, scientific secretary: F. Steinhäusler, University of Salzburg, Austria). The IRMP is designed to assess and foster the improvement of radon and decay product measurements that are made around the world. Within the framework of the IRMP, the U.S. Environmental Protection Agency Radiation and Indoor Environments National Laboratory (EPA) in Las Vegas, Nevada, organized jointly with the U.S. Bureau of Mines an international intercomparison exercise at a former uranium mine (Twilight Mine, Colorado) and the EPA Radon Laboratory. The main objective of this exercise was to compare radon and radon decay product instruments under both well-controlled as well as widely fluctuating exposure conditions. The laboratory exposures occurred under relatively steady radon and decay product conditions, with a moderate equilibrium ratio, while the conditions in the mine fluctuated greatly and the equilibrium ratio was low. An additional purpose of the exercise was to provide a forum for manufacturers and measurement organizations worldwide to exchange information and plan improvements in their operations and calibration programs. Altogether 19 organizations from seven countries intercomparing 32 different radon and radon decay product instruments participated in this exercise. This paper summarizes the results from the analysis of the experimental data obtained in the Bureau of Mines Twilight Mine in July of 1994, as well as the results from the EPA Radon laboratory in August of 1994.

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.

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.

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.