The outcome of the Lithuanian radon survey.
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The results of field investigations of natural radiation exposures of the general population in two stable rural communities in Yugoslavia are presented. The principal emphasis was on exposures to contemporary indoor radon, but measurements of external penetrating radiation absorbed dose rates in air were carried out in the majority of cases. In addition, in a limited number of dwellings, measurements of thoron gas concentrations were made. By means of making a series of sequential 3-month radon measurements, both seasonal variations and annual average radon levels in the dwellings were determined. Using passive alpha track detectors, individual radon and thoron indoor concentrations as high as 9591 Bq m(-3) and 709 Bq m(-3), respectively, were detected while absorbed dose rates in air in the dwellings as high as 430 nGy h(-1) were recorded. On the basis of these different types of measurements, assessments could be made of the integrated natural radiation exposures being received by the populations. In addition to contemporary radon measurements, retrospective radon exposure assessments in most of the dwellings were made on the basis of measurements of 210Po concentrations in both surface (glass) traps and in volume (porous materials) traps. A description is given of the sampling strategies and protocols used in this field work. It is shown that at least one stable rural community receiving high natural radiation exposures, has been clearly identified and plans for future health investigations of the population there are outlined.
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.
Since the discovery of x rays, the public has shown increasing concern about exposure to radiation. In the mid-1980s, with the dissemination of information about the ubiquitous nature of radon, this concern about radiation exposure has taken on a new perspective. As the general public realizes that exposure to radiation is an unavoidable part of life, questions arise as to how much exposure is acceptable when weighed against the costs of reducing the exposure. Because limited resources are available to protect the public's health and the environment, these resources need to be used wisely. The cost-effectiveness of the various options to lessen the potential adverse health effects from radon must be considered.
Mitigation of radon gas and radon progeny in buildings is based largely on reducing the pressure difference between the point of the radiation source and the point of entry to indoor air. This study identifies the influence of mechanical systems, of air-conditioning and 'wet' systems of central heating as potential remediation agents in the control of radon and progeny concentrations. Air-conditioning was found to reduce radon levels in a systematic way within a few hours of start-up, to a low fraction of the immediately preceding concentration. Central heating reduced the level by around 40% of the preceding high within a few hours of start-up. Importantly for health concerns, under operating conditions of both types of system the level of radon progeny was reduced to a greater extent than the radon progenitor.
Lung-cancer risk to the general population from indoor radon remains controversial, although studies of radon exposure have established that radon decay products have been a cause of lung cancer among miners. For the case group of patients, suffering from lung cancer, and the control group distributions of the number of homes with high indoor levels of radon were compared with the log-normal distribution, the empirical frequency distribution of the control group obeyed the theoretical log-normal distribution. Using the ratio of frequencies of the case group to the control groups, or the relative frequencies, an association between the relative frequencies and indoor radon concentrations was found, and a positive correlation coefficient was obtained, thus enabling the rate of lung cancer to be estimated for certain indoor radon concentrations. The significant difference between the mean radon levels for the case sample and the control led to the conclusion that patients with lung cancer lived in homes with radon concentrations which were significantly higher than those of Osijek's inhabitants for the control sample.
Ionizing radiation dose levels due to home radon can rise to levels that would be illegal for workers in the nuclear industry. It is well known that radon levels within homes and from home to home, and also from month to month, vary considerably. To define an Isle of Man radon seasonal correction factor, readings were taken in eight homes over a 12 month period. An average island indoor exposure of 48 Bq m(-3) (range 4-518 Bq m(-3)) was determined from 285 homes selected from a cohort of 1300 families participating in the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) in the Isle of Man. This compares with a UK home average of 20 Bq m(-3) and a European Union average (excluding UK) of 68 Bq m(-3). Ten homes of those measured were found to have radon levels above the National Radiological Protection Board 200 Bq m(-3) action level. There are 29,377 homes on the Isle of Man, suggesting that there could be some 900 or more homes above the action level. No statistical difference was found between the NRPB and Isle of Man seasonal correction factors.
The existence of 85Kr in the air is primarily due to the reprocessing of nuclear fuel. The two major reprocessing plants in the western world are at La Hague in France and Sellafield in the UK. Prior to the commissioning of THORP at Sellafield in 1994, a programme to monitor the concentration of 85Kr in air at Clonskeagh, Dublin was commenced. While results for the measurements over the period 1993-1997 indicate that the concentration of 85Kr in the air is increasing, it has not been possible to link any particular measurement result to a krypton release from the Sellafield site. The concentration of 85Kr in air, at the existing level, does not present a significant radiological hazard. Exposure to 85Kr, which is an inert gas, results mainly in small doses to the skin. A mean annual concentration of 1.34 Bq m(-3) was calculated for 1997 which would result in a skin dose of 0.55 microSv for the year to the exposed skin of an individual.
In the UK, Action Levels for radon have been established at 400 Bq m(-3) for the workplace and 200 Bq m(-3) for the home. We have estimated the dose received by occupants of rooms with radon levels near or above the Action Level, using hourly radon readings, and a questionnaire to record occupancy. In the workplace, results for 73 staff suggest that doses are lower than expected, partly due to part-time working and partly due to the mobility of staff. The 75% quantile for the series, corrected to a 37 hour week, is 5.2 mSv at 400 Bq m(-3). Compared to the current annual limit for radiation workers, the Action Level could be increased, but the current Action Level is compatible with the recent EEC Directive requiring a lower dose limit. However, when raised radon levels in the workplace were reduced by remediation in the series we studied, the dose reduction to staff was consistently around half of the radon level reduction. Although it would be appropriate to study more locations, this suggests an Action Level for remediated workplaces of 200 Bq m(-3). Finally, in a limited series of dose assessments in domestic properties, we found that doses could considerably exceed 5 mSv at the 200 Bq m(-3) Action Level, primarily because the sample included an example of high occupancy, in our case several Asian wives in purdah, whose occupancy was almost total.
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In this paper the focus is on Arnea Chalkidikis, an area in Greece with granitic geological background and indications of possible elevated radon concentration indoors. Data are reported of indoor radon measurements with etched track detectors and those are used for dosimetric estimations. Moreover, data are reported on soil gas and soil radon concentrations in Arnea, as well as radon and uranium concentrations in water samples. From the measured radon concentrations in water samples the contribution to the overall dose has been calculated. For a period of 1 month, indoor radon and progeny activity has also been monitored in the dwelling that has the maximum indoor radon concentration in Greece. This dwelling is in Arnea and the dose delivered to the inhabitants has been calculated. The mean annual effective dose due to indoor radon was 4.5 mSv and about 11% of this was due to the use of water. Mean soil gas concentration and soil radon concentration were (90 +/- 30) kBq m(-3) (p<0.05) and (30 +/- 5) kBq m(-3) (p<0.05) respectively. Mean uranium concentration of the water samples was (98 +/- 13) mBq l(-1) (p<0.05).
The results of a first phase of an indoor radon survey in a total of 1610 dwellings distributed in nine cities of the Eastern and the Western provinces of Saudi Arabia are presented. The objective of this radon survey was to obtain representative indoor radon data for seven cities in the Eastern province. Khafji, Hafr Al-Batin, Abqaiq, Qatif, Al-Ahsa, Dammam and Khobar and to compare this with two cities in the Western province, Madina and Taif. So far, detailed radon data is not available for Saudi Arabia: therefore, this radon survey provides a base line for Saudi Arabia in the Radon World Atlas. On average, 200 indoor radon dosemeters were distributed in each city and placed for a period of one year starting from May 2001 to May 2002. The total number of collected dosemeters was 847. A total of 724 houses and 98 schools were covered in this survey. The results of the survey in the cities showed that the overall minimum, maximum and average radon concentrations were 1, 137 and 22 Bq m(-3), respectively. Geometric mean and geometric standard deviations of the radon distribution were found to be 18 and 1.92, respectively. In one of the dwellings in Qatif city, radon concentration, measured by a passive system and then confirmed by an active system, was found to be 535 +/- 23 and 523 +/- 22 Bq m(-3), respectively. The result of a radon survey in 98 schools showed that the minimum, maximum and average radon concentrations were 1, 70 and 19 Bq m(-3), respectively. The average radon concentration for each city was also determined. The lowest average radon concentration (8 Bq m(-3)) was found in Al-Ahsa while the highest average concentration (40 Bq m(-3)) was found in Khafji.
The radon concentration has been measured for three years in a hospital cave used for medical treatment of respiratory diseases. A mean value of the actual equilibrium factor measured in the cave in different seasons was used, different from the commonly used 0.4. The dose contribution to the patients and the staff was calculated using these data. The results of the dose assessment show that the staff in the hospital cave can receive doses up to the dose limit for occupational exposure (20 mSv y(-1)) when working 4 h per day in the cave. Patients receive 0.18-4.22 mSv committed effective dose during the treatment period depending on the exposure periods. The only solution to reduce the dose to the staff seems to be decreasing the time they spend underground, because intensive ventilation would disturb the special microclimate of the cave.
Due to its long physical half-life, and the fact that its long-term mobility in the environment as well as its radiotoxicity is higher than that of 137Cs, the long-term bio-availability of 90Sr in the environment is of importance with regard to the long-term population exposure after fallout from nuclear weapons detonations or a severe reactor accident. It will also substantially influence the time-span required until re-utilisation of highly contaminated territory is possible again. An assessment of the long-term decrease of the activity concentration in all foodstuffs relevant for internal exposure after severe 90Sr fallout was performed. The observed effective half-lives were approximately 1.8-2.1 years in the first 2-3 years after the end of fallout and 8-10 years in the following three decades. This is equivalent to a biological half-life of about 13.2 years and results in a total 50 year dose of 6.2 times the first year exposure. Due to this decline in 90Sr-availability, the average annual activity intake of 90Sr in Austria has decreased from 840 Bq at the climax of the nuclear weapons tests to about 42 Bq in 1997 for adults, and from 500 Bq to about 35 Bq for 1 year old infants. This is equivalent to a 90Sr ingestion dose of 1.2 microSv for adults and 2.5 microSv for 1 year old infants in 1997 or less than 0.4% of the ingestion dose by natural radionuclides in the diet.
Radon and gamma dose rates were surveyed in five Slovenian spas, at Rogaska Slatina, Radenci, Moravci, Podcetrtek, and Catez. Due to effective ventilation systems, the indoor air radon concentration rarely exceeds 200 Bq x m(-3) and is usually lower. Uncer the present operationsal conditions and working regimes of the spas, there is no basis for concern about elevated exposure of personnel to radon.
Different parameters enter models of the human respiratory tract. The unattached fraction of the radon progeny was identified as the most important parameter, with the strongest influence on lung dose. The unattached fraction depends on the indoor aerosol concentration and other environmental conditions. The recoil factor, p, which influences the unattached fraction of 214Pb and 214Bi, defined as the average detachment probability from the aerosol after an alpha decay of 218Po, has almost always been taken as a constant. Here the recoil factor was recalculated under different assumptions and found to be in the range between 0.1 and 0.8. A smaller recoil factor means lower unattached fractions of 214Pb and 214Bi. The influence of the recoil factor on lung dose was also estimated. The lung dose is smaller by about 10% if p = 0.1 is assumed in calculating the unattached fraction instead of p = 0.8.
The results of measurement of atmospheric radon concentration in Beijing, China, are reported. Continuous observation was performed hourly throughout 2003 to provide data on annual average radon concentration as well as the variation of radon concentration. An arithmetic annual mean value of 14.1 +/- 5.5 Bq m(-3) was obtained. The value was slightly higher than the world average and the national average. For the monthly average radon concentration, the maximum was 18.5 +/- 5.0 Bq m(-3) in November, while the minimum was 9.9 +/- 4.1 Bq m(-3) in May. Diurnal variation was also observed, and the average daily pattern of radon concentration consisted of a minimum in the late afternoon and a maximum in the early hours of the morning.
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