EXPOSURE LEVELS OF UKRAINIAN POPULATION IN THE CONTEXT OF AN ACTION PLAN TO REDUCE INDOOR RADON LEVELS. / RIVNI OPROMINENNIa NASELENNIa UKRAÏNY V KONTEKSTI PLANU DII ShchODO ZMENShENNIa RIVNIV RADONU V POVITRI PRYMIShchEN'.

OBJECTIVE: To analyze and evaluate the available information to indoor radon concentration in the context of theimplementation of the radon action plan. OBJECT OF STUDY: indoor radon-222 in dwellings by area and corresponding radiation risks of the population. Measurements were performed using passive track radonometry. The exposure time of the radonometers is atleast 30 days during heating season. Radiation risk calculations were performed according to the dose coefficientsand mathematical models of the ICRP. RESULTS: It was found that for the whole country, reference level 300 Bq/m3 (radon gas) is exceeded in 16 % ofcases. It was found that geometric mean of radon gas levels was 120 Bq/m3 and varies from 35 to 265 Bq/m3 bydifferent area, namely the difference between radon levels in different territories of the country can be up to 7.5times. Variability of radon levels at the district level is also significant. It was found, radon activity concentrationdiffering by almost 10 times by districts with lognormal distribution and a geometric mean of 75 Bq/m3. The analy-sis of radiation risks of the population has established that estimated annual number of lung cancer deaths due toradon in Ukraine is almost 8,900 cases; and а direct economic loss for the country are estimated at more than $450 million a year. CONCLUSIONS: Surveys of radon levels demonstrated significant variation in radon concentrations between different regions. For the whole country, reference level (300 Bq/m3) is exceeded on above 16 % of the dwellings, butpercentage of exceeding varies from 0.1 to 43.0 % by different area. Information on indoor radon concentrationsin almost a third of the country is non-available. For an effective implementation of the Action plan, it makes sense to introduce radon risk mapping.

Estimates of the Lung Cancer Cases Attributable to Radon in Municipalities of Two Apulia Provinces (Italy) and Assessment of Main Exposure Determinants.

Indoor radon exposure is responsible for increased incidence of lung cancer in communities. Building construction characteristics, materials, and environmental determinants are associated with increased radon concentration at specific sites. In this study, routine data related to radon measurements available from the Apulia (Italy) Regional Environmental Protection Agency (ARPA) were combined with building and ground characteristics data. An algorithm was created based on the experience of miners and it was able to produce estimates of lung cancer cases attributable to radon in different municipalities with the combined data. In the province of Lecce, the sites with a higher risk of lung cancer are Campi Salentina and Minervino, with 1.18 WLM (working level months) and 1.38 WLM, respectively, corresponding to lung cancer incidence rates of 3.34 and 3.89 per 10 × 10³ inhabitants. The sites in the province of Bari with higher risks of lung cancer are Gravina di Puglia and Locorotondo, measuring 1.89 WLM and 1.22 WLM, respectively, which correspond to an incidence rate of lung cancer of 5.36 and 3.44 per 10 × 10³ inhabitants. The main determinants of radon exposure are whether the buildings were built between 1999 and 2001, were one-room buildings with porous masonry, and were built on soil consisting of pelvis, clayey sand, gravel and conglomerates, calcarenites, and permeable lithotypes.

CANADIAN POPULATION RISK OF RADON INDUCED LUNG CANCER-VARIATION RANGE ASSESSMENT BASED ON VARIOUS RADON RISK MODELS.

To address public concerns regarding radon risk and variations in risk estimates based on various risk models available in the literature, lifetime lung cancer risks were calculated with five well-known risk models using more recent Canadian vital statistics (5-year averages from 2008 to 2012). Variations in population risk estimation among various models were assessed. The results showed that the Canadian population risk of radon induced lung cancer can vary from 5.0 to 17% for men and 5.1 to 18% for women based on different radon risk models. Averaged over the estimates from various risk models with better radon dosimetry, 13% of lung cancer deaths among Canadian males and 14% of lung cancer deaths among Canadian females were attributable to long-term indoor radon exposure.

Assessment of personal airborne exposures and surface contamination from x-ray vaporization of beryllium targets at the National Ignition Facility.

This article presents air and surface sampling data collected over the first two years since beryllium was introduced as a target material at the National Ignition Facility. Over this time, 101 experiments with beryllium-containing targets were executed. The data provides an assessment of current conditions in the facility and a baseline for future impacts as new, reduced regulatory limits for beryllium are being proposed by both the Occupational Safety and Health Administration and Department of Energy. This study also investigates how beryllium deposits onto exposed surfaces as a result of x-ray vaporization and the effectiveness of simple decontamination measures in reducing the amount of removable beryllium from a surface. Based on 1,961 surface wipe samples collected from entrant components (equipment directly exposed to target debris) and their surrounding work areas during routine reconfiguration activities, only one result was above the beryllium release limit of 0.2 µg/100 cm2 and 27 results were above the analytical reporting limit of 0.01 µg/100 cm2, for a beryllium detection rate of 1.4%. Surface wipe samples collected from the internal walls of the NIF target chamber, however, showed higher levels of beryllium, with beryllium detected on 73% and 87% of the samples during the first and second target chamber entries (performed annually), respectively, with 23% of the samples above the beryllium release limit during the second target chamber entry. The analysis of a target chamber wall panel exposed during the first 30 beryllium-containing experiments (cumulatively) indicated that 87% of the beryllium contamination remains fixed onto the surface after wet wiping the surface and 92% of the non-fixed contamination was removed by decontaminating the surface using a dry wipe followed by a wet wipe. Personal airborne exposures assessed during access to entrant components and during target chamber entry indicated that airborne beryllium was not present in workers' breathing zones. All the data thus far have shown that beryllium has been effectively managed to prevent exposures to workers during routine and non-routine work.

Mutagenic potential assessment associated with human exposure to natural radioactivity.

Lucrécia city, known to harbor a high cancer rate, is located in a semiarid region characterized by the presence of mineral reservoirs, facing a high exposure to metal and natural radioactivity. The present study aimed to assess the environmental scenario at a semiarid region located in Northeastern Brazil. Metal concentration, alpha and beta radiation, and cyanobacteria content in tap water along with indoor radon and gamma emitters (U, K and Th) concentrations were measured. In addition, mutagenic and nuclear instability effects were assessed using buccal micronucleus cytome assay. The study included five samplings corresponding to a period between 2007 and 2009. Drinking water from Lucrécia city presented levels of Mn, Ni and Cr along with cyanobacteria in concentrations one to four times higher than regulatory guidelines considered. Furthermore, high levels of all the tested radionuclides were found. A high percentage of the houses included in this study presented indoor radon concentrations over 100 Bq m-3. The mean annual effective dose from Lucrécia houses was six times higher than observed in a control region. The levels of exposure in most of the Lucrécia houses were classified as middle to high. A significant mutagenic effect, represented as an increase of micronuclei (MN) frequency and nuclear abnormalities as nuclear buds (NB), binucleated cells (BN), and pyknotic cells (PYC) were found. The results obtained highlight the role of high background radioactivity on the observed mutagenic effect and could help to explain the exacerbated cancer rate reported in this locality.

Radon induced hyperplasia: effective adaptation reducing the local doses in the bronchial epithelium.

There is experimental and histological evidence that chronic irritation and cell death may cause hyperplasia in the exposed tissue. As the heterogeneous deposition of inhaled radon progeny results in high local doses at the peak of the bronchial bifurcations, it was proposed earlier that hyperplasia occurs in these deposition hot spots upon chronic radon exposure. The objective of the present study is to quantify how the induction of basal cell hyperplasia modulates the microdosimetric consequences of a given radon exposure. For this purpose, computational epithelium models were constructed with spherical cell nuclei of six different cell types based on histological data. Basal cell hyperplasia was modelled by epithelium models with additional basal cells and increased epithelium thickness. Microdosimetry for alpha-particles was performed by an own-developed Monte-Carlo code. Results show that the average tissue dose, and the average hit number and dose of basal cells decrease by the increase of the measure of hyperplasia. Hit and dose distribution reveal that the induction of hyperplasia may result in a basal cell pool which is shielded from alpha-radiation. It highlights that the exposure history affects the microdosimetric consequences of a present exposure, while the biological and health effects may also depend on previous exposures. The induction of hyperplasia can be considered as a radioadaptive response at the tissue level. Such an adaptation of the tissue challenges the validity of the application of the dose and dose rate effectiveness factor from a mechanistic point of view. As the location of radiosensitive target cells may change due to previous exposures, dosimetry models considering the tissue geometry characteristic of normal conditions may be inappropriate for dose estimation in case of protracted exposures. As internal exposures are frequently chronic, such changes in tissue geometry may be highly relevant for other incorporated radionuclides.

Soil gas radon assessment and development of a radon risk map in Bolsena, Central Italy.

Vulsini Volcanic district in Northern Latium (Central Italy) is characterized by high natural radiation background resulting from the high concentrations of uranium, thorium and potassium in the volcanic products. In order to estimate the radon radiation risk, a series of soil gas radon measurements were carried out in Bolsena, the principal urban settlement in this area NE of Rome. Soil gas radon concentration ranges between 7 and 176 kBq/m(3) indicating a large degree of variability in the NORM content and behavior of the parent soil material related in particular to the occurrence of two different lithologies. Soil gas radon mapping confirmed the existence of two different areas: one along the shoreline of the Bolsena lake, characterized by low soil radon level, due to a prevailing alluvial lithology; another close to the Bolsena village with high soil radon level due to the presence of the high radioactive volcanic rocks of the Vulsini volcanic district. Radon risk assessment, based on soil gas radon and permeability data, results in a map where the alluvial area is characterized by a probability to be an area with high Radon Index lower than 20 %, while probabilities higher than 30 % and also above 50 % are found close to the Bolsena village.

A look at the grouping effect on population-level risk assessment of radon-induced lung cancer.

On the basis of considerable knowledge gained by studying health effects in uranium and other underground miners who worked in radon-rich environments, radon exposure has been identified as a cause of lung cancer. Recent pooled analyses of residential studies have shown that radon poses a similar risk of causing lung cancer in the general public when exposure occurs at generally lower levels found in homes. With the increasing accessibility of statistical data via the internet, people are performing their own analyses and asking why, in some cases, the lung cancer occurrence at the community level does not correlate to the radon levels. This study uses statistical data available to the general public from official websites and performs simple analyses. The results clearly show the difficulty in linking observed lung cancer incidence rates at the provincial/territorial level, with possible cause, such as smoking or radon exposure. Even the effect of smoking, a well-documented cause of lung cancer, can be overlooked or misinterpreted if the data being investigated is too general (i.e., summary data at population level) or is influenced by other factors. These difficulties with simple comparisons are one of the main reasons that epidemiological studies of lung cancer incidence and radon exposure requires the use of cohorts or case controls at the individual level as opposed to the more easily performed ecological studies at the population level.

Allometric methodology for the assessment of radon exposures to terrestrial wildlife.

A practical approach to calculate (222)Rn daughter dose rates to terrestrial wildlife is presented. The method scales allometrically the relevant parameters for respiration in different species of wildlife, allowing inter-species calculation of the dose per unit radon concentration in air as simple base-and-exponent power functions of the mass. For plants, passive gas exchange through the leaf surface is assumed, also leading to specific power relationships with mass. The model generates conservative predictions in which the main contributor to the dose rate of target tissues of the respiratory system is from α radiation arising from (222)Rn daughters. Tabulated (222)Rn DPURn values are given for 69 species used by the England & Wales Environment Agency for habitats assessments. The approach is then applied to assess the authorised discharges of (222)Rn from sites in England, demonstrating that, from a whole-body dose perspective, the biota considered are protected from effects at the population level.

Modeling joint exposures and health outcomes for cumulative risk assessment: the case of radon and smoking.

Community-based cumulative risk assessment requires characterization of exposures to multiple chemical and non-chemical stressors, with consideration of how the non-chemical stressors may influence risks from chemical stressors. Residential radon provides an interesting case example, given its large attributable risk, effect modification due to smoking, and significant variability in radon concentrations and smoking patterns. In spite of this fact, no study to date has estimated geographic and sociodemographic patterns of both radon and smoking in a manner that would allow for inclusion of radon in community-based cumulative risk assessment. In this study, we apply multi-level regression models to explain variability in radon based on housing characteristics and geological variables, and construct a regression model predicting housing characteristics using U.S. Census data. Multi-level regression models of smoking based on predictors common to the housing model allow us to link the exposures. We estimate county-average lifetime lung cancer risks from radon ranging from 0.15 to 1.8 in 100, with high-risk clusters in areas and for subpopulations with high predicted radon and smoking rates. Our findings demonstrate the viability of screening-level assessment to characterize patterns of lung cancer risk from radon, with an approach that can be generalized to multiple chemical and non-chemical stressors.

Assessment of intakes and doses to workers followed for 15 years after accidental inhalation of 60CO.

Intakes and doses are assessed for seven workers who accidentally inhaled particles containing Co in the same incident. Comprehensive whole body data to 15 y, and some early urine and fecal data, are available for each individual. The biokinetic and dosimetric models currently recommended by ICRP have been used to assess these cases. It was not possible to obtain good fits to the data using the ICRP models with their default parameter values. However, good fits to all the measurement data were obtained by varying parameter values following a procedure similar to that recommended in recently developed guidelines for assessment of internal doses from monitoring data. It was found that retention in the lungs was much longer than predicted by the ICRP Human Respiratory Tract Model, and so for each case it was necessary to reduce the particle transport clearance of material from the deep lungs. This reduction in lung clearance rates, and the use of specific AMAD values, were the dominating factors in changing assessed doses from those calculated using ICRP default values.

Assessment and prevention of radioactive risk due to 222Radon on University Premises in Genoa, Italy.

From October 2004 to September 2005, Radon222 activity in high-risk indoor spaces used by employees and students at the University of Genoa was measured with CR-39 nuclear track detectors. The mean concentration in winter (78.9 Bq/m3 +/- 74.92 S.D.) was low in relation to the microenvironment considered. When data were broken down by type and location of the spaces, no significant differences were found, despite the fact that the Genoa conurbation lies on soil of variable geological composition. The dose absorbed by employees was 0.42 mSv/year, with a relative risk of 4.2/1000 cases of Radon-related lung cancer. The dose absorbed by students was 0.28 mSv/year, with a relative risk of 2.5/1000 cases of Radon-related lung cancer. The level of radon activity detected never exceeded the limit of 500 Bq/m3 established by Italian law. Nevertheless, the value of the compound uncertainty index suggested that the real level of Radon contamination could have exceeded 400 Bq/m3 in selected spaces, a value requiring annual concentration tests.

Interaction of alpha particles at the cellular level--implications for the radiation weighting factor.

Since low dose effects of alpha particles are produced by cellular hits in a relatively small fraction of exposed cells, the present study focuses on alpha particle interactions in bronchial epithelial cells following exposure to inhaled radon progeny. A computer code was developed for the calculation of microdosimetric spectra, dose and hit probabilities for alpha particles emitted from uniform and non-uniform source distributions in cylindrical and Y-shaped bronchial airway geometries. Activity accumulations at the dividing spur of bronchial airway bifurcations produce hot spots of cellular hits, indicating that a small fraction of cells located at such sites may receive substantially higher doses. While presently available data on in vitro transformation frequencies suggest that the relative biological effectiveness for alpha particles ranges from about 3 to 10, the effect of inhomogeneous activity distributions of radon progeny may slightly increase the radiation weighting factor relative to a uniform distribution. Thus a radiation weighting factor of about 10 may be more realistic than the current value of 20, at least for lung cancer risk following inhalation of short-lived radon progeny.

Assessment of health risks to skin and lung of elevated radon levels in abandoned mines.

Radon, together with its progeny, is present in high levels in some underground sites. Radon is known to increase the risk of lung cancer, while increased levels of radon decay products on the skin surface have been implicated in skin cancer induction and at sufficient levels might cause deterministic effects such as erythema. Although radon levels in working mines are controlled, radon in abandoned mines can reach very high levels, which would result in an occupant exceeding recommended annual exposure limits in less than 2 h in some mines. The relative importance of dose limits for the lung, skin cancer, and deterministic effects is discussed in the light of practical experience.

Evaluation of the NESHAP radiological risk assessment.

The Environmental Protection Agency performed a risk assessment as a basis for the National Emission Standards for Hazardous Air Pollutants. This paper compares the Environmental Protection Agency's risk assessment with the models used by the National Research Council's fifth Committee on the Biological Effects of Ionizing Radiations, the United Nations Scientific Committee on the Effects of Atomic Radiation, and the International Commission on Radiological Protection. Comparison of the parameters used by each organization suggests that the Environmental Protection Agency could improve its own risk assessment by adopting one of the assessments done by the BEIR V Committee, the United Nations Scientific Committee on the Effects of Atomic Radiation, and the International Commission on Radiological Protection.

Critical considerations in the assessment of health and environmental risks - what we have learned from the nuclear experience.

The radiological experience has produced some sophisticated approaches to estimating the environmental risks of anthropogenic chemicals, based on well-validated models for both health effects and exposure assessment. As to exposure assessment, site- and situation-specific data must be acquired for quantitative predictions. However, the requirements for quantitative estimation are often overlooked, even with the radiological models. Metabolism or other chemical processes, also, may more profoundly alter a chemical contaminant than they would a radioelement. Suitably developed models provide useful guidance in deciding what kinds of data to get and how extensive particular data bases need to be.