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.     

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.     

Biologically induced Po emission from fresh water

Behavior of Po in fresh waters was examined in laboratory culture experiments using fresh water collected from a small pool, Xi river and Xiqing lake, showing formation of volatile Po compounds followed by emission to air. Addition of tryptone to the fresh water cultures increased the emission of Po considerably along with a growth of microorganisms, suggesting a connection of chemoheterotrophs to Po emission. Participation of photoautotrophs was also considered because Po emission was increased when NaHCO3 was added to the fresh water cultures. The emission behavior of Po and S in these experiments appeared in different ways. The quantity of Po emitted was comparable to the previous culture experiments (Momoshima, Song, Osaki & Maeda, Environ. Sci. Technol., 35, 2956-2960, 2001) in which artificial culture medium containing 3% NaCl was used and inoculated with sea sediment extract. The biological support for Po emission, thus, would be a general phenomenon in fresh water as well as a seawater environment and is possibly a source for atmospheric Po.     

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.     

Activities of 210Po and 210Pb in the water column at Kuala Selangor, Malaysia

Natural radionuclides, such as (210)Po and (210)Pb were measured in the water samples collected from six stations at Kuala Selangor, Malaysia. Results for (210)Po and (210)Pb in dissolved and particulate phases have showed the difference in distribution and chemical behavior. The fluctuation activities of (210)Po and (210)Pb depend on wave action, geology and degree of fresh water input occurring at study areas and probably due to different sampling dates. The distribution coefficient, K(d), values of (210)Po and (210)Pb ranged from 2.0 x 10(3)lg(-1) to 265.15 x 10(5)lg(-1), and from 3.0 x 10(3)lg(-1) to 558.16 x 10(5)lg(-1), respectively. High K(d) values of (210)Po and (210)Pb indicated that a strong adsorption of (210)Po and (210)Pb onto suspended particles, and the sinking of both nuclides on the seabed at study locations were controlled by the characteristics of suspended particles.     

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).     

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.     

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.     

High (210)Po atmospheric deposition flux in the subtropical coastal area of Japan

Bulk atmospheric deposition fluxes of (210)Po and (210)Pb were measured at three coastal regions of Japan, the Pacific Ocean coastal area of the Japanese mainland (Odawa Bay), the Chinese continental side of Japanese coastal area (Tsuyazaki), and an isolated island near Okinawa (Akajima). Wet and dry fallout collectors were continuously deployed from September 1997 through August 1998 for periods of 3 to 31 days depending on the frequency of precipitation events. Annual (210)Pb deposition fluxes at Odawa Bay (35 degrees N 139 degrees E), Tsuyazaki (33 degrees N 130 degrees E) and Akajima (26 degrees N 127 degrees E) were 73.3+/-8.0, 197+/-35 and 78.5+/-8.0 Bqm(-2)y(-1), respectively. Higher (210)Pb deposition was observed at the Chinese continental side of Japanese coast than at the Pacific Ocean coastal site. The high (210)Pb atmospheric flux at the Chinese continental side coast was thought to be attributable to (222)Rn-rich air-mass transport from the Chinese continent during the winter monsoon. In contrast, the annual (210)Po deposition fluxes at the three study sites were 13.0+/-2.3 (Odawa Bay), 21.9+/-4.4 (Tsuyazaki) and 58.4+/-7.7 (Akajima)Bqm(-2)y(-1), respectively, indicating unusual high (210)Po deposition at Akajima during winter. Anomalous unsupported (210)Po input was observed during summer 1997, suggesting unknown source of (210)Po at this area.     

Bioaccumulation of polonium 210Po in marine birds

The aim of this work was to determine the 210Po content in marine birds which permanently or temporally live in the Polish part of the Baltic Sea. We chose 11 species of sea birds: three species permanently residing at southern Baltic Sea, four species of wintering birds and three species of migrating birds. The results show that the polonium is non-uniformly distributed in the marine birds. The highest activities of 210Po were observed in feathers, muscles and liver and the lowest in skin and skeleton. Species of birds that eat crustaceans, molluscs, fish and plants (long-tailed duck Clangula hyemalis, white-winged scoter Melanitta fusca) accumulated more polonium than species that eat mainly fish (great cormorant Phalacrocorax carbo, common guillemot Uria aalge) or plants (tufted duck Aythya fuligula). Moreover, about 63% of the 210Po that was located in feathers of razorbil (Alca torda) and long-tailed duck (C. hyemalis) was apparently adsorbed, suggesting an external source such as the air. It means that the adsorption of 210Po on the feather surface may be an important transfer from air to water.     

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.     

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.     

Distribution of (226)Ra-(210)Pb-(210)Po in marine biota and surface sediments of the Red Sea, Sudan

Activity concentration levels and ratios of (226)Ra, (210)Pb and (210)Po are presented in multicellular marine algae, molluscs, coral as well as in surface marine sediments collected from the shallower waters of the fringing reefs area extending towards north and south (Flamingo bay) of PortSudan harbour, Sudan. The analyses were performed adopting alpha-spectrometry, liquid scintillation and Cerenkov counting techniques. Surface sediments from this coastal region are poor in their radioactivity content in contrast to similar data reported from different coastal areas around the globe. There is surface enrichment of (210)Pb and (210)Po with respect to their progenitor (226)Ra as it is evident from the activity ratios of (210)Pb/(226)Ra (3.03+/-1.79) and (210)Po/(226)Ra (2.23+/-1.56). Among marine plants and animals investigated, the green algae species, Halimeda, and coral species, Favites, show substantial concentration of radium at 8.2Bq/kg and 21.9Bq/kg dry weight, respectively. Similarly, the highest concentration of (210)Po was met in Favites at 38.7Bq/kg followed by brown algae, Cystoseria sp., at 32.6Bq/kg. There is no variation seen among algal species for (210)Pb uptake, however, converse to radium and polonium, Favites (coral) was found to contain the minimum concentration of lead (3.88Bq/kg). In most species there is preferential accumulation of polonium over its parent radium as indicated by (210)Po:(226)Ra activity ratio with Cystoseria (brown algae) showing the highest value at 8.81. On the other hand, (210)Po:(210)Pb activity concentration ratio revealed that coral species Favites (9.97) and the brown algae Sargassum (1.85) have a greater tendency to accumulate (210)Po over (210)Pb, while in the rest of species; this ratio is less than unity.     

210Po concentration in Perna perna mussels: looking for radiation effects

Twenty ropes with 400 Perna perna mussels seeds (3 cm shell size) were set-up on floating structures at Cabo Frio Island, Arraial do Cabo, approximately 100 km northeast of Rio de Janeiro city. A rope was taken out on a monthly basis, and the shell sizes of 100 seeds were measured. The haemolymph of 10 male and 10 female individuals was taken, and the same individuals were separated for 210Po/210Pb determination. After one year of monthly sampling, no clear correlation was observed between the 210Po concentration, mussel's age and weight. A mean 210Po concentration of 155 Bq kg(-1) wet weight basis, was obtained, which is comparable with data reported in the literature. The radiation dose did not have any observable effect on the micronuclei frequency and DNA breaks in the mussels. This was probably due to the low dose rate, 0.02 mGy d(-1), in comparison with the suggested potential dose limit of 10 mGy d(-1).     

Evaluation of 210Pb and 210Po in cigarette tobacco produced in Brazil

Cigarette smoking is one of the pathways that might contribute significantly to the increase in the radiation dose reaching man, due to the relatively large concentrations of 210Pb and 210Po found in tobacco leaves. In the present study, the concentrations of these two radionuclides were determined in eight of the most frequently sold cigarette brands produced in Brazil. 210Pb was determined by counting the beta activity of 210Bi with a gas flow proportional detector after radiochemical separation and precipitation of PbCrO4. 210Po was determined by alpha spectrometry using a surface barrier detector after radiochemical separation and spontaneous deposition of Po on a copper disk. The results showed concentrations ranging from 11.9 to 30.2 mBq per gram of dry tobacco for 210Pb and from 10.9 to 27.4 mBq per gram of dry tobacco for 210Po. The collective committed effective dose resulting from the use of cigarettes produced in Brazil per year is estimated to be 1.5 x 10(4) man-Sv.     

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.     

Transfer factors of Polonium from soil to parsley and mint

Transfer factors of ²¹⁰Po from soil to parsley and mint have been determined. Artificial polonium isotope (²⁰⁸Po) was used as a tracer to determine transfer factor of Po from soil to plant in pot experiments. Two plant growing systems were used for this study namely, an outdoor system and a sheltered system by a polyethylene tent. ²⁰⁸Po and ²¹⁰Po were determined in soil and different parts of the studied plants (stem and leaf), using alpha spectroscopy. The results have shown that there was a clear uptake of ²⁰⁸Po by roots to leaves and stems of both plants. Higher values of transfer factors using the ²¹⁰Po activity concentrations than the ²⁰⁸Po activity concentration were observed. Transfer factors of ²¹⁰Po from soil to parsley varied between 20 × 10⁻² and 50 × 10⁻² and 22 × 10⁻³ and 67 × 10⁻³ in mint, while ²⁰⁸Po transfer factors varied between 4 × 10⁻² and 12 × 10⁻² for parsley and 10 × 10⁻² and 22 × 10⁻² in mint. Transfer factors of Po were higher in those plants grown in the sheltered system than in the open system; about 75% of Po was transferred from atmosphere to parsley parts using the two systems. Ratios of transferred Po from soil to mint stem and leaf in the sheltered system were higher by 2 times from those in the open system.     

The subcellular localization of natural 210Po in the hepatopancreas of the rock lobster (Jasus lalandii)

The subcellular localization of the naturally occuring nuclide ²¹⁰Po in the hepatopancreas of the South African rock lobster, Jasus lalandii, has been studied using centrifugation, ultrafiltration and chromatography. Just over half of the ²¹⁰Po was found to be associated with a component in the microsomal pellet. Most of the ²¹⁰Po was tightly bound to a component of high molecular mass (10⁷ daltons or greater). Dissociation of the ²¹⁰Po from this component required incubation with sulphydryl-reducing reagents, after which the ²¹⁰Po appeared to associate with a fraction having a molecular mass of 1500 daltons or less. A search for negatively-charged, hydrophobic, sulphur-containing membrane proteins which bind ²¹⁰Po is suggested.     

Po determination in urines of people living in Central Italy

This paper presents the results of the monitoring programme on the urines of people living in an area of Central Italy (near the Republic of S. Marino) to evaluate the background level of the ²¹⁰Po excretion rate (mBq day⁻¹) in this region. The volunteers were subdivided in five age classes and in every age class groups of males and females, cigarette smokers and non-smokers were taken into account. The results indicated that the ²¹⁰Po excretion rate was widely distributed within each group of volunteers. The ²¹⁰Po excretion rate was <30 mBq day⁻¹ for 93.2% of people. The obtained results are discussed and some conclusion, based upon the average values, was drawn.     

Detection of 210Po on filter papers 16 years after use for the collection of short-lived radon progeny in a room

Radon gas was allowed to accumulate in its radium source and then injected into a 36 m(3) test room, resulting in an initial radon concentration of 15 kBq m(-3). Filter papers were used to collect the short-lived radon progeny and thus to measure the Potential Alpha Energy Concentration (PAEC) in-situ in the year 1984 at different times and conditions according to the experimental design. The radon progeny collected on the filter papers were studied as a function of aerosol particle concentration ranging from 10(2)-10(5) particles cm(-3) in three different experiments. The highest aerosol particle concentration was generated by indoor cigarette smoking. Those filters were stored after the experiment, and were used after 16 years to study the activity of the radon long-lived alpha emitter progeny, (210)Po (T(1/2)=138 days). This isotope is separated from the short-lived progeny by (210)Pb beta emitter with 22.3 years half-life. After 16 years' storage of these filters, each filter paper was sandwiched and wrapped between two CR-39 nuclear track detectors, to put the detectors in contact with the surfaces of different filters, for 337 days. Correlation between the PAEC measured using filter papers in the year 1984 and the activity of long-lived alpha emitter (210)Po on the same filter papers measured in the year 2000 were studied. The results of the (210)Po activity showed a very good correlation of 0.92 with the PAEC 16 years ago. The results also depict that the PAEC and (210)Po activity in indoor air increased with the increase of aerosol particle concentration, which shows the attachment of short-lived radon progeny with the aerosol particles. The experiment proves that indoor cigarette smoking is a major source of aerosol particles carrying radon progeny and, thus, indoor cigarette smoking is an additional source of internal radiation hazard to the occupants whether smoker or non-smoker.