Concentration levels of 210Pb and 210Po in dry tobacco leaves in Greece

Tobacco leaves are large and have sticky exudates that retain the radon decay products once they deposit on the leaves. The study of 210Po in tobacco is required, because of the cumulative alpha-radiation dose delivered to humans from inhaled 210Po in cigarette smoke. 210Pb is the other element of interest since it is the 210Po precursor in the radioactive decay chain. In the present study, the concentrations of these two radionuclides were determined in tobacco samples from seven regions in Greece. 210Po was determined by alpha spectrometry using a surface barrier detector after radiochemical separation and spontaneous deposition of polonium on a nickel disk. The 210Pb activity in the samples was determined via the 210Po resulting from the decay of 210Pb. The results of the present study indicate that 210Po concentrations ranged from 3.6 to 17.0 mBqg(-1) (average 13.1 mBqg(-1)) of dry tobacco, while 210Pb concentrations ranged from 7.3 to 18.0 mBqg(-1) (average 13.4 mBqg(-1)). The mean value of the annual committed effective dose for smokers (20 cigarettes per day) of Greek tobacco was estimated to be 287 microSv (124 microSv from 210Po and 163 microSv from 210Pb). The inhalation dose for smokers is on average about 12 times higher than for non-smokers living in the mid-latitudes of the northern hemisphere.     

Polonium-210 budget in cigarettes

Due to the relatively high activity concentrations of (210)Po and (210)Pb that are found in tobacco and its products, cigarette smoking highly increases the internal intake of both radionuclides and their concentrations in the lung tissues. That might contribute significantly to an increase in the internal radiation dose and in the number of instances of lung cancer observed among smokers. Samples of most frequently smoked fine and popular brands of cigarettes were collected from those available on the Egyptian market. (210)Po activity concentrations were measured by alpha spectrometry, using surface barrier detectors, following the radiochemical separation of polonium. Samples of fresh tobacco, wrapping paper, fresh filters, ash and post-smoking filters were spiked with (208)Po for chemical recovery calculation. The samples were dissolved using mineral acids (HNO(3), HCl and HF). Polonium was spontaneously plated-out on stainless steel disks from diluted HCl solution. The (210)Po activity concentration in smoke was estimated on the basis of its activity in fresh tobacco and wrapping paper, fresh filter, ash and post-smoking filters. The percentages of (210)Po activity concentrations that were recovered from the cigarette tobacco to ash, post-smoking filters, and smokes were assessed. The results of this work indicate that the average (range) activity concentration of (210)Po in cigarette tobacco was 16.6 (9.7-22.5) mBq/cigarette. The average percentages of (210)Po content in fresh tobacco plus wrapping paper that were recovered by post-smoking filters, ash and smoke were 4.6, 20.7 and 74.7, respectively. Cigarette smokers, who are smoking one pack (20 cigarettes) per day, are inhaling on average 123 mBq/d of (210)Po and (210)Pb each. The annual effective doses were calculated on the basis of (210)Po and (210)Pb intake with the cigarette smoke. The mean values of the annual effective dose for smokers (one pack per day) were estimated to be 193 and 251 microSv from (210)Po and (210)Pb, respectively.     

Inhalation of 210Po and 210Pb from cigarette smoking in Poland.

The carcinogenic etfect of 210Po and 210Pb with respect to lung cancer is an important problem in many countries with very high cigarette consumption. Poland has one of the highest consumptions of cigarettes in the world. The results of 210Po determination on the 14 most frequently smoked brands of cigarettes which constitute over 70% of the total cigarette consumption in Poland are presented and discussed. Moreover, the polonium content in cigarette smoke was estimated on the basis of its activity in fresh tobaccos, ash, fresh filters and post-smoking filters. The annual effective doses were calculated on the basis of 210Po and 210Pb inhalation with the cigarette smoke. The results of this work indicate that Polish smokers who smoke one pack (20 cigarettes) per day inhale from 20 to 215 mBq of 210Po and 210Pb each. The mean values of the annual effective dose for smokers were estimated to be 35 and 70 microSv from 210Po and 210Pb, respectively. For persons who smoke two packs of cigarettes with higher radionuclide concentrations, the effective dose is much higher (471 microSv yr(-1)) in comparison with the intake in diet. Therefore, cigarettes and the absorption through the respiratory system are the main sources and the principal pathway of 210Po and 210Pb intake of smokers in Poland.     

Study of 210Po and 210Pb in the riverine environments of coastal Karnataka

Activity of ²¹⁰Po and ²¹⁰Pb were measured in soil and sediment samples collected from the major rivers Kali, Sharavathi and Netravathi of Coastal Karnataka. The activity of these two radionuclides were determined by radiochemical separation of ²¹⁰Po and counting the activity using a ZnS(Ag) Alpha counter. The activity of ²¹⁰Pb was higher than that of ²¹⁰Po in the riverine environs. The ²¹⁰Po and ²¹⁰Pb content in sediment was found to increase with silt/clay and organic matter contents. However no significant correlation was found between the activity ²¹⁰Po and ²¹⁰Pb with pH in sediments. The activity of ²¹⁰Po and ²¹⁰Pb and influence of physico-chemical parameters on these radionuclides were studied and discussed in this paper.     

Technologically enhanced 210Pb and 210Po in iron and steel industry

Iron and steel manufacture has been ranked as the largest industrial source of environmental contamination in the USA; the wastes generated in their production processes contain heavy elements that can be a source of contamination, and natural radionuclides that can produce an occupational and/or public radiological impact. In this work the potential occupational effective dose rate (μSv/y) due to inhalation in four integrated steel-making factories from Egypt has been evaluated, by assuming a well defined scenario and with basis in the ²¹⁰Pb and ²¹⁰Po activity concentrations determined in ore and wastes collected in the aforementioned factories. Activity concentrations, in Bq/kg, of ²¹⁰Pb and ²¹⁰Po, and leachable Pb and Fe were measured using gamma-ray spectrometry based on HPGe detector, alpha particle spectrometry based on PIPS detector, and inductively coupled plasma-mass spectrometry (ICP-MS). Levels of ²¹⁰Pb and ²¹⁰Po in the range of <DL-4238 and 1-5660 Bq/kg, respectively, were found. According to the assumed scenarios, the occupational exposures by inhalation are much lower than the recommended annual effective dose limit, although the environmental impact due to waste storage and/or use should be considered based on case by case evaluation.     

Studies on the distribution of 210Po and 210Pb in the ecosystem of Point Calimere Coast (Palk Strait), India

A systematic study on the natural radionuclides such as 210Po and 210Pb in the environmental matrices of Point Calimere ecosystem has been undertaken to establish a baseline data on the radiation profile of Point Calimere environment. The environmental samples such as water, sediment and biota (seaweeds, crustaceans, molluscs and fish) have been subjected to analyses. It has been observed that the concentration of 210Po and 210Pb in the water samples of Point Calimere to be 0.5 mBq/l and 1.3 mBq/l, respectively. The soft tissues of the organisms accumulated higher 210Po content while shells and bones contained more 210Pb. The bivalve molluscs Meretrix casta have been identified to accumulate higher concentration of 210Po suggesting that they could serve as bio-indicator of radionuclides like 210Po in the Point Calimere ecosystem. The concentration factor of 210Po for the biotic components ranged from approximately 10(3) to 10(6) while for 210Pb it ranged from approximately 10(3) to 10(5).     

Variation of the activity concentrations and fluxes of natural (210Po, 210Pb) and anthropogenic (239,240Pu, 137Cs) radionuclides in the Strait of Gibraltar (Spain)

The activity concentrations and fluxes of natural (210Pb, 210Po) and anthropogenic (239,240Pu, 137Cs) radionuclides have been determined in the different water masses crossing the Strait of Gibraltar. New data have been gathered during four multidisciplinary and multinational sampling campaigns, performed between 1997 and 1999 within the framework of the CANIGO-FLUGIST Project. Mean activity concentrations of 210Po (1.53+/-0.34 Bq m(-3), n = 30) and 210Pb (1.16+/-0.50 Bq m(-3), n = 31) in the Atlantic water entering the Mediterranean basin are about double those measured in the Mediterranean outflow, namely 0.84+/-0.34 Bq m(-3) (n = 22) for 210Po and 0.66+/-0.34 Bq m(-3) (n = 22) for 210Pb. The opposite trend is observed for 231,240Pu, with average concentrations of 9.9+/-3.0 mBq m(-3) (n = 29) in the incoming Atlantic flow and 22.0+/-3.0 mBq m(-3) (n = 22) in the outpouring Mediterranean water. In the case of 137Cs, the same concentrations were quantified in the waters moving inwards (2.52+/-0.28 Bq m(-3), n = 27) and outwards (2.14+/-0.52 Bq m(-3), n = 21) from the Mediterranean Sea. On this basis, the Mediterranean basin experiences a net annual input flux of 14 TBq of 210Pb and 19 TBq of 210Po, and a net annual loss of 0.34 TBq of 239,240Pu, while--at present--137Cs input and output fluxes appear to be balanced.     

Aspects on the analysis of 210Po

There has been little development regarding analysis of polonium (Po) in environmental samples since the 1960ies. This is due to the straightforward spontaneous deposition of this element on silver (Ag), nickel (Ni) or copper (Cu) without any radiochemical separation. For many years, no radiochemical yield determinant was used and it was generally supposed that the yield was 100% after two depositions. Counting was often done using ZnS scintillation counter coupled to a photomultiplier tube. However, the use of the yield determinants ²⁰⁸Po and ²⁰⁹Po and the development of alpha spectrometry showed that the yield was lower. Furthermore, the tendency of Po to volatilize at low temperatures constrains the sample preparation techniques; dry-ashing cannot be used. But during the wet-ashing procedure, there are still some losses.The aim of this study was to evaluate the Po losses during wet-ashing by the use of a double-tracer technique. We have found that the losses were about 30% when open glass beakers were used and about 17% when the samples were digested in microwave oven. When long-necked bottles (Kjeldahl flasks) were used, a loss of about 20% was registered.It has also been observed that ²¹⁰Pb to some extent is plating out together with its daughter nuclide Po during the electrochemical deposition. This will result in a systematic error since an unknown amount of supported ²¹⁰Po will be produced from the ²¹⁰Pb decay depending on the fraction of ²¹⁰Pb being deposited on the disc and the waiting time between deposition and measurement of the sample. A further consequence of this is that in the assessment of the ²¹⁰Pb content in the sample, very often the remaining liquid is stored after deposition for build-up of ²¹⁰Po. Since some ²¹⁰Pb is lost on the disc, the result for ²¹⁰Pb will be too low. Both these systematic errors give rise to a too high ²¹⁰Po/²¹⁰Pb ratio. The fraction of ²¹⁰Pb which is plating out has been assessed in this study for different matrices and is about 50-90%. During the measurement by solid state Si-detectors, some Po is evaporated in the vacuum conditions contaminating the detectors. Experiments have here been done by heating the discs after deposition which indicate that less Po is evaporated from Ag than from Ni. The losses from Ag are less than that from the other metals probably due to a deeper penetration into the surface of Po. We conclude that in most aspects, Ag is better to use than the other plating metals.     

Speciation of 210Po and 210Pb in air particulates determined by sequential extraction

Speciation of (210)Po and (210)Pb in air particulates of two Syrian phosphate sites with different climate conditions has been studied. The sites are the mines and Tartous port at the Mediterranean Sea. Air filters were collected during September 2000 until February 2002 and extracted chemically using different selective fluids in an attempt to identify the different forms of these two radionuclides. The results have shown that the inorganic and insoluble (210)Po and (210)Pb (attached to silica and soluble in mineral acids) portion was found to be high in both sites and reached a maximum value of 94% and 77% in the mine site and Tartous port site, respectively. In addition, only 24% of (210)Pb in air particulates was found to be associated with organic materials probably produced from the incomplete burning of fuel vehicle and similar activities. Moreover, the (210)Po/(210)Pb activity ratio in air particulates was higher than that in all samples at both sites and varied between 3.85 in November 2000 at Tartous port site and 20 in April 2001 at the mine area. These activity ratios were also higher than the natural levels. The (210)Po/(210)Pb activity ratio was also determined in each portion resulting from the selective extraction and found to be higher than that in most samples. The sources of (210)Po excess in these portions are discussed. Soil suspension, which is common in the dry climate dominant in the area, sea water spray and heating of phosphate ores were considered; polonium is more volatile than the lead compounds at even moderate temperature. Furthermore, variations in the chemical forms of (210)Po and (210)Pb during the year were also investigated. However, the results of this study can also be utilized for dose assessment to phosphate industry workers.     

Reinvestigation of airborne 210Pb, 137Cs and 207Bi in Vienna (Austria) after atmospheric nuclear weapons tests

Reconstruction of atmospheric 210Pb and 137Cs activity concentrations occurring in Vienna immediately after the atmospheric nuclear weapons tests shall answer the question, whether artificial 210Pb has been produced by fusion devices using lead materials. If so, 207Bi also can be expected. In 1962, weekly average values for 210Pb were between 0.08 +/- 0.02 and 1.31 +/- 0.30 mBq/m2, 137Cs amounts up to 5.1 +/- 0.6 mBq/m3. 207Bi remains below the detection limit, viz. < 0.5 mBq/m3. Bimonthly averages for the periods 1962-1964 and 1974-1975 show 137Cs activity concentrations with typical springtime maxima occurring together with low 210Pb values and 207Bi < 0.02 mBq/m3. Annual averages of 210Pb are varying between 0.27 and 0.53 mBq/m3, independent of whether atmospheric tests have been performed or not. Comparison of the activity ratios 207Bi/210Pb, 207Bi/137Cs and 210Pb/137Cs with published data, leads to the conclusion that no evidence exists for a significant production of 210Pb by nuclear explosions, neither after the Soviet tests in 1961-1962 nor after the Chinese tests in 1973-1976.     

210Pb and 210Po in Finnish cereals

A survey was carried out on the activity concentrations of ²¹⁰Pb and ²¹⁰Po in cereal grains produced in Finland. The cereal species were wheat (Triticum aestivum), rye (Secale cereale), oats (Avena sativa) and barley (Hordeum vulgare), which account for 90% of the Finnish consumption of cereal products. The survey consisted of 18 flour and 13 unprocessed cereal samples and one hulled grain sample from 22 flour mills. According to the results, the mean ²¹⁰Pb/²¹⁰Po concentrations in wheat grains, wheat flour, rye flour, oat grains and barley grains were 0.29, 0.12, 0.29, 0.36 and 0.36 Bq kg⁻¹, respectively. Combined with the consumption rates of the products, we assess that the mean effective doses from ²¹⁰Pb and ²¹⁰Po in cereal products for the adult male and female population are 22 and 17 μSv per year, respectively.     

Factors affecting 210Po and 210Pb activity concentrations in mussels and implications for environmental bio-monitoring programmes

The activity of ²¹⁰Po and ²¹⁰Pb was determined in mussels of the same size (3.5-4.0 cm shell length) sampled monthly over a 17-month period at the Atlantic coast of Portugal. Average radionuclide concentration values in mussels were 759 ± 277 Bq kg⁻¹ for ²¹⁰Po (range 460-1470 Bq kg⁻¹ dry weight), and 45 ± 19 Bq kg⁻¹ for ²¹⁰Pb (range 23-96 Bq kg⁻¹ dry weight). Environmental parameters and mussel biometric parameters were monitored during the same period. Although there was no seasonal variation of radionuclide concentrations in sea water during the study period, the concentration of radionuclide activity in mussels varied seasonally displaying peaks of high concentrations in winter and low concentrations in summer. Analysis of radionuclide data in relation to the physiological Condition Index of mussels revealed that ²¹⁰Po and ²¹⁰Pb activities in the mussel (average activity per individual) remained nearly constant during the investigation period, while mussel body weight fluctuated due to fat storage/expenditure in the soft tissues. Similar variation of radionuclide concentrations was observed in mussels transplanted from the sea coast into the Tejo Estuary. However, under estuarine environmental conditions and with higher food availability throughout the year, transplanted mussel Condition Index was higher than in coastal mussels and average radionuclide concentrations were 210 ± 75 Bq kg⁻¹ (dry weight) for ²¹⁰Po and 10 ± 4 Bq kg⁻¹ (dry weight) for ²¹⁰Pb, therefore lower than in coastal mussels with similar shell length. It is concluded that the apparent seasonal fluctuation and inter-site difference of radionuclide concentrations were mostly caused by mussel body weight fluctuation and not by radionuclide body burden fluctuation. This interpretation can be extended to the apparent seasonal fluctuation in concentrations of lipophilic and lipophobic contaminants in mussels, and provides an explanation for occasional high concentrations of ²¹⁰Po and man-made contaminants measured in mussels far from pollution sources.     

The impact of phosphate loading activities on near marine environment: the Syrian coast.

The impact of loading cargoes of phosphate ore into ships on the near marine environment at the Syrian coast has been evaluated. Results have shown a significant enhancement of 210Po, 210Pb and other natural radionuclides in sediment and surface water inside the port area. The highest 210Po and 210Pb concentrations observed in sediment were found to be 170 and 64 Bq kg(-1) respectively, while 210Pb and 210Po concentrations in surface water ranged from 5 to 20 mBq l(-1) and 0.93 to 3.23 mBq l(-1). In addition, comparable values of 210Po and 210Pb for all marine organisms (algae, crab and fish) suggest that their use as indicators for phosphate pollution is not recommended. However, the effect of loading cargoes on the port marine environment of Tartous was found to be mainly related to wind direction where radioactive air particulate are either being dispersed to land or sea.     

Natural radionuclides in Austrian mineral water and their sequential measurement by fast methods

Ten samples of Austrian mineral water were investigated with regard to the natural radionuclides (228)Ra, (226)Ra, (210)Pb, (210)Po, (238)U and (234)U. The radium isotopes as well as (210)Pb were measured by liquid scintillation counting (LSC) after separation on a membrane loaded with element-selective particles (Empore Radium Disks) and (210)Po was determined by alpha-spectroscopy after spontaneous deposition onto a copper planchette. Uranium was determined by ICP-MS as well as by alpha-spectroscopy after ion separation and microprecipitation with NdF(3). From the measured activity concentrations the committed effective doses for adults and babies were calculated and compared to the total indicative dose of 0.1 mSv/a given in the EC Drinking Water Directive as a maximum dose. The dominant portion of the committed effective dose was due to the radium isotopes; the dose from (228)Ra in most samples clearly exceeded the dose from (226)Ra.     

Daily ingestion of 232Th, 238U, 226Ra, 228Ra and 210Pb in vegetables by inhabitants of Rio de Janeiro City

The concentrations of the naturally occurring radionuclides 232Th, 238U, 210Pb, 226Ra and 238Ra were determined in the vegetables (leafy vegetables, fruit, root, bean and rice) and derived products (sugar, coffee, manioc flour, wheat flour, corn flour and pasta) consumed most by the adult inhabitants of Rio de Janeiro City. A total of 88 samples from 26 different vegetables and derived products were analyzed. The highest contribution to radionuclide intake arises from bean, wheat flour, manioc flour, carrot, rice, tomato and potato consumption. The estimated daily intakes due to the consumption of vegetables and derived products are 1.9 mBq of 232Th (0.47 microg), 2.0 mBq of 238U (0.17 microg), 19 mBq of 236Ra, 26 mBq of 210Pb and 47 mBq of 228Ra. The estimated annual effective dose due to the ingestion of vegetables and their derived products with the long-lived natural radionuclides is 14.5 microSv. Taking into account literature data for water and milk from Rio de Janeiro the dose value increases to 29 microSv, with vegetables and derived products responsible for 50% of the dose and water for 48%. 210Pb (62%) and 228Ra (24%) were found to be the main sources for internal irradiation.     

Transfer of (40)K, (238)U, (210)Pb, and (210)Po from soil to plant in various locations in south of Syria

Transfer factors of (40)K, (238)U, (210)Pb, and (210)Po from soil to some agriculture crops in various locations in south of Syria (Dara'a and Assuwaydaa districts) have been determined. Soil and vegetable crops (green pepper, cucumber, tomato, and eggplant), legumes crops (lentil, chickpea, and broad bean), fruit trees (apple, grape, and olives) and cereals (barley and wheat) were collected and analyzed for (238)U, (210)Pb, and (210)Po. The results have shown that higher transfer factors (calculated as Bqkg(-1) dry wt. plant material per Bqkg(-1) dry wt. soil) for (210)Po, (210)Pb and (238)U were observed in vegetable leaves than fruits and cereals leaves; the highest values of transfer factor (TF) for (238)U were found to be 0.1 for straw of chickpea. Transfer factors for (210)Po varied between 2.8x10(-2) and 2 in fruits of eggplant and grain of barley, respectively. In addition, several parameters affecting transfer factors of the radionuclides were evaluated. The results can be considered as base values for TF of natural radionuclides in the region.     

Polonium-210 and lead-210 in the terrestrial environment: a historical review

The radionuclides ²¹⁰Po and ²¹⁰Pb widely present in the terrestrial environment are the final long-lived radionuclides in the decay of ²³⁸U in the earth’s crust. Their presence in the atmosphere is due to the decay of ²²²Rn diffusing from the ground. The range of activity concentrations in ground level air for ²¹⁰Po is 0.03-0.3 Bq m⁻³ and for ²¹⁰Pb 0.2-1.5 Bq m⁻³.In drinking water from private wells the activity concentration of ²¹⁰Po is in the order of 7-48 mBq l⁻¹ and for ²¹⁰Pb around 11-40 mBq l⁻¹. From water works, however, the activity concentration for both ²¹⁰Po and ²¹⁰Pb is only in the order of 3 mBq l⁻¹.Mosses, lichens and peat have a high efficiency in capturing ²¹⁰Po and ²¹⁰Pb from atmospheric fallout and exhibit an inventory of both ²¹⁰Po and ²¹⁰Pb in the order of 0.5-5 kBq m⁻² in mosses and in lichens around 0.6 kBq m⁻². The activity concentrations in lichens lies around 250 Bq kg⁻¹, dry mass.Reindeer and caribou graze lichen which results in an activity concentration of ²¹⁰Po and ²¹⁰Pb of about 1-15 Bq kg⁻¹ in meat from these animals. The food chain lichen-reindeer or caribou, and Man constitutes a unique model for studying the uptake and retention of ²¹⁰Po and ²¹⁰Pb in humans. The effective annual dose due to ²¹⁰Po and ²¹⁰Pb in people with high consumption of reindeer/caribou meat is estimated to be around 260 and 132 μSv a⁻¹ respectively.In soils, ²¹⁰Po is adsorbed to clay and organic colloids and the activity concentration varies with soil type and also correlates with the amount of atmospheric precipitation. The average activity concentration levels of ²¹⁰Po in various soils are in the range of 20-240 Bq kg⁻¹.Plants become contaminated with radioactive nuclides both by absorption from the soil (supported Po) and by deposition of radioactive fallout on the plants directly (unsupported Po). In fresh leafy plants the level of ²¹⁰Po is particularly high as the result of the direct deposition of ²²²Rn daughters from atmospheric deposition. Tobacco is a terrestrial product with high activity concentrations of ²¹⁰Po and ²¹⁰Pb. The overall average activity concentration of ²¹⁰Po is 13 ± 2 Bq kg⁻¹. It is rather constant over time and by geographical origin.The average median daily dietary intakes of ²¹⁰Po and ²¹⁰Pb for the adult world population was estimated to 160 mBq day⁻¹ and 110 mBq day⁻¹, corresponding to annual effective doses of 70 μSv a⁻¹ and 28 μSv a⁻¹, respectively. The dietary intakes of ²¹⁰Po and ²¹⁰Pb from vegetarian food was estimated to only 70 mBq day⁻¹ and 40 mBq day⁻¹ corresponding to annual effective doses of 30.6 μSv a⁻¹ and 10 μSv a⁻¹, respectively. Since the activity concentration of ²¹⁰Po and ²¹⁰Pb in seafood is significantly higher than in vegetarian food the effective dose to populations consuming a lot of seafood might be 5-15 fold higher.     

Radiological hazards of Narghile (hookah, shisha, goza) smoking: activity concentrations and dose assessment

Narghile (hookah, shisha, goza, "water-pipe") smoking has become fashionable worldwide. Its tobacco pastes, known as moassel and jurak, are not standardized and generally contain about 30-50% (sometimes more) tobacco, molasses/juice of sugarcane, various spices and dried fruits (particularly in jurak) and, in the case of moassel, glycerol and flavoring essences. Tobacco contains minute amounts of radiotoxic elements such as (210)Pb, (210)Po and uranium, which are inhaled via smoking. Only very few data have been published on the concentrations of natural radionuclides in narghile tobacco mixtures. Consequently, the aim of this study was to draw first conclusions on the potential hazards of radioactivity in moassel tobacco in relation to narghile smoking. The results indicate the existence of a wide range in the radioactivity contents where the average (range) activity concentrations of (238)U, (234)Th (226)Ra, (210)Pb, (210)Po, (232)Th and (40)K, in Bq/kg dry weight were 55 (19-93), 11 (3-23), 3 (1.2-8), 14 (3-29), 13 (7-32), 7 (4-10) and 719 (437-1044)Bq/kg dry weight, respectively. The average concentrations of natural radionuclides in moassel tobacco pastes are comparable to their concentration in Greek cigarettes and tobacco leaves, and lower than that of Brazilian tobacco leaves. The distribution pattern of these radionuclides after smoking, between smoke, ash and filter, is unknown, except for (210)Po during cigarette smoking and from one existing study during moassel smoking. Radiological dose assessment due to intake of natural radionuclides was calculated and the possible radio-toxicity of the measured radionuclides is briefly discussed.     

Po-210 and Pb-210 as atmospheric tracers and global atmospheric Pb-210 fallout: a review

Over the past ∼5 decades, the distribution of ²²²Rn and its progenies (mainly ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po) have provided a wealth of information as tracers to quantify several atmospheric processes that include: i) source tracking and transport time scales of air masses; ii) the stability and vertical movement of air masses iii) removal rate constants and residence times of aerosols; iv) chemical behavior of analog species; and v) washout ratios and deposition velocities of aerosols. Most of these applications require that the sources and sink terms of these nuclides are well characterized.Utility of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po as atmospheric tracers requires that data on the ²²²Rn emanation rates is well documented. Due to low concentrations of ²²⁶Ra in surface waters, the ²²²Rn emanation rates from the continent is about two orders of magnitude higher than that of the ocean. This has led to distinctly higher ²¹⁰Pb concentrations in continental air masses compared to oceanic air masses. The highly varying concentrations of ²¹⁰Pb in air as well the depositional fluxes have yielded insight on the sources and transit times of aerosols. In an ideal enclosed air mass (closed system with respect to these nuclides), the residence times of aerosols obtained from the activity ratios of ²¹⁰Pb/²²²Rn, ²¹⁰Bi/²¹⁰Pb, and ²¹⁰Po/²¹⁰Pb are expected to agree with each other, but a large number of studies have indicated discordance between the residence times obtained from these three pairs. Recent results from the distribution of these nuclides in size-fractionated aerosols appear to yield consistent residence time in smaller-size aerosols, possibly suggesting that larger size aerosols are derived from resuspended dust. The residence times calculated from the ²¹⁰Pb/²²²Rn, ²¹⁰Bi/²¹⁰Pb, and ²¹⁰Po/²¹⁰Pb activity ratios published from 1970’s are compared to those data obtained in size-fractionated aerosols in this decade and possible reasons for the discordance is discussed with some key recommendations for future studies.The existing global atmospheric inventory data of ²¹⁰Pb is re-evaluated and a ‘global curve’ for the depositional fluxes of ²¹⁰Pb is established. A current global budget for atmospheric ²¹⁰Po and ²¹⁰Pb is also established. The relative importance of dry fallout of ²¹⁰Po and ²¹⁰Pb at different latitudes is evaluated. The global values for the deposition velocities of aerosols using ²¹⁰Po and ²¹⁰Pb are synthesized.     

137Cs and 210Po dose assessment from marine food in Cienfuegos Bay (Cuba)

One part of Radiological Monitoring Programme in central Cuba (1991-1995) was dedicated to study the background levels of natural and anthropogenic radioactivity in Cienfuegos Bay in the vicinity of the first Cuban nuclear power station under construction. 210Po and 137Cs concentrations in fish, molluscs and crustaceans collected in Cienfuegos Bay were determined and the committed effective doses (CED) were calculated for two population groups inhabiting this region. The highest values of 210Po concentrations were found in crustaceans, but significant accumulation was also observed in fish and molluscs. The mean 137Cs concentrations in organisms are several times lower with respect to 210Po, a situation that characterises the regions affected by the global fallout only. Values of CED from the consumption of crustaceans and molluscs are very low both from 210Po and 137Cs. The mean individual dose from 210Po in the seafood consumed varies from 39 microSv for general populations to 2802 microSv for the "critical group" consuming 320 kg of fish per year. The dose from 137Cs is negligible.