The activity of 210Pb in cigarette smoked in Kazakhstan.

The radon decay product 210Pb is a known component of tobacco. In this study, the activity concentration of 210Pb in the most popular cigarette brands (six samples) for Kazakhstan consumers was determined by beta spectrometry. The activity levels of 210Pb ranged between 2.69 ± 0.27 and 27.42 ± 2.74 mBq per cigarette. Higher activity concentrations for 210Pb were found in Sample No.4 and showed an excess of the world average by 1.8 times. The average activity concentrations of 210Pb in cigarette tobacco were 10.42 ± 1.04 mBq cig-1. The daily activities inhaled in the lungs of a smoker, and the resulting effective doses due to cigarette smoking were calculated. Effective doses per year due to cigarette smoking were calculated assuming that 42.13% of the 210Pb in tobacco were retained in the lungs of the smokers. It is concluded that for a smoker in Kazakhstan, the average effective dose ranges from 9.1 ± 0.9 µSv/year to 92.8 ± 9.3 µSv/year for a cigarette consumption of one pack of cigarettes per day. The results indicate that the annual effective doses from inhalation of 210Pb due to smoking one pack of cigarettes per day are from 7 to 58 times (for different types of cigarettes) greater than the annual effective doses from ingestion of radionuclides via the diet.

210Po and 210Pb radioactivity levels in local and imported tobacco used in Palestine and Jordan.

This study aimed to assess the concentrations of 210Po and 210Pb in various tobacco samples from Palestine and Jordan. Cigarette smoking is recognized as a significant contributor to the radiation dose received by individuals, primarily due to the elevated levels of 210Pb and 210Po found in tobacco. The analysis revealed that the average concentrations of 210Po in locally sourced tobacco and cigarette samples in Palestine are 16.8 ± 2.3 mBq/g and 18.5 ± 2.0 mBq/g, with a total average of 17.8 ± 7.4 mBq/g (15.5 mBq/cigarette). Similarly, the average concentrations of 210Pb in these samples are 18.5 ± 2.6 mBq/g and 20.3 ± 2.2 mBq/g, with a total average of 19.6 ± 8.1 mBq/g (17.0 mBq/cigarette). In Jordan, the average concentrations of 210Po in cigarette samples and narghile tobacco are 20.1 ± 2.4 mBq/g and 18.3 ± 4.1 mBq/g, with a total average value of 19.6 ± 9.9 mBq/g (18.0 mBq/cigarette), while the average concentrations of 210Pb are 22.2 ± 2.6 mBq/g and 20.2 ± 4.5 mBq/g, with a total average value of 21.6 ± 10.8 mBq/g (19.9 mBq/cigarette). The annual effective doses resulting from inhalation were calculated for smokers of these samples. The findings revealed that the levels of 210Po and 210Pb radioactivity in certain investigated samples exceeded the results of studies in many countries of the world. The associated effective doses per year from smoking for all brands products in Palestine range from 34.7 µSv/y to 186.5 µSv/y with an average of 109.5 µSv/y, while in Jordan 54.5 µSv/y to 289.1 µSv/y with an average of 130.9 µSv/y.

The concentration of radioisotopes (Potassium-40, Polonium-210, Radium-226, and Thorium-230) in fillet tissue carp fishes: A systematic review and probabilistic exposure assessment.

Chemical contamination of seafood has become a global health concern. Carp fish is one of the most widely consumed globally, and several studies have been conducted on the contamination of carp fish with radioisotopes. In the current study, a meta-analysis and probabilistic exposure assessment regarding the Potassium-40 (40K), Polonium-210 (210Po), Radium-226 (226Ra), and Thorium-230 (230Th) in the fillet tissue of carp fish were performed. In this regard, Scopus and PubMed were screened to retrieve the associated citations with on the concentration of radioisotopes in the fillet tissue of carp fish until October 2021. The rank order of radioisotopes in fillet tissue carp fish was 40K (103.49 Bq kg-1) > 210Po (9.39 Bq kg-1) > 226Ra (0.62 Bq kg-1) > 230Th (0.39 Bq kg-1). The highest effective dose due to 210Po ingestion was observed in Spain (male; 4.44E-05 Sv y-1, female; 2.67E-06 Sv y-1); 40K (female, 5.07E-07 Sv y-1); 226Ra (male, 9.93E-09 Sv y-1). The mean of effective dose (ED) in the male and females in India due to ingestion of 230Th as result of carp fish consumption was (1.70E-06 Sv y-1) and (7.01E-08 Sv y-1), respectively. The probabilistic exposure assessment by the Monte Carlo simulation method revealed that consumers of fillet tissue carp fish content of radioisotopes are at a safe range (0.001 Sv y-1).

Assessment of Be-7, Pb-210 and Po-210 Activities in Airborne Particulate Matter Over Istanbul, Türkiye.

Airborne particulate matter is one of the air pollutants which can have detrimental health effects in the human body. Radionuclides adsorb onto air particles and make their way to humans primarily through inhalation. Naturally-occurring radionuclides, 210Pb and 210Po, are of notable health concern due to their relatively elevated ingestion and inhalation doses. In the current study, activity concentrations of 7Be, 210Pb and 210Po were determined in air particulate matter (PM). PM2.5 was collected on the European side, while PM10 was collected on the Anatolian side of Istanbul. Be-7, 210Pb and 210Po activities were found to be 5.17 ± 2.35, 0.96 ± 0.42; 0.25 ± 0.14 mBq m- 3 in Anatolian side, respectively. Be-7, 210Pb and 210Po activities were found to be 3.81 ± 2.27, 0.62 ± 0.29, 0.29 ± 0.26, mBq m- 3 in European side, respectively. The ratio of 210Po/210Pb was found to be higher (0.47 ± 0.31 for PM2.5 and 0.34 ± 0.27 for PM10) than the global average of 0.1. This result can be explained by the fact that Po is more volatile than Pb and enhanced in the air by the combustion process. Inhalation dose rates of 210Pb and 210Po due to PM10 exposure were calculated to be 7.70 ± 3.30 and 4.05 ± 2.31 µSv year- 1, respectively. Pb-210 bioaccessibility was assessed by the extraction of the particles in simulated lung fluids. Approximately 24.8% of inhaled 210Pb was estimated to be bioaccessible. This study suggests that 210Po and 210Pb activities are partially enhanced in the air particles in Istanbul and should be regularly monitored.

Factors Contributing to Accumulation of 210Po in Freshwater Fishes in Dong Thai Lake, Vietnam and Radiological Hazard Assessment.

210Po (polonium), one of the most toxic naturally occurring radionuclides, is well-known as a common natural radionuclide in fish species. Human consumption of 210Po-contaminated fish could result in a significant internal dose. This study determined by alpha spectrometry the 210Po activity in sixteen selected fish species with different living behaviors (pelagic, demersal), trophic positions (herbivores, carnivores, omnivorous), and masses in Dong Thai Lake, Hanoi, Vietnam. The min, max, and average of the 210Po concentration of sixteen fish species were 0.80 ± 0.44, 12.7 ± 0.20, and 3.54 ± 0.31 Bq kg-1, respectively. Regarding the different living behaviors, trophic positions, and masses, the results showed trending of 210Popelagic > 210Podemersal; 210Poherbivores < 210Pocarnivores < 210Poomnivorous and 210Po<0.2 kg > 210Po0.2-1 kg > 210Po>1 kg, respectively. The 210Po concentrations in muscle tissue were greater in fish species with a small mass, omnivorous trophic position, and pelagic living behavior relative to demersal fish with a larger mass that were herbivores or carnivores. In addition, the results showed an uneven distribution of 210Po activities in atmospheric aerosols, terrestrial soils, surface waters, and lake sediments in the study area. The primary source of 210Po could be supplied from atmospheric aerosols and/or terrestrial soils in the study area. The 210Po annual effective dose for adults due to fish consumption has been calculated with a range from 20 to 400 µSv y-1 and 111 µSv. y-1 on average, and it is far below the allowable limits of 1000 µSv y-1.

Detection of Polonium-210 in Environmental, Biological and Food Samples: A Review.

Ingestion of polonium-210 from environmental media and food can cause serious health hazards (e.g., gastrointestinal symptoms, tumours, etc.) and has been a public health concern worldwide since the 2006 poisoning of Agent Litvinenko 210Po in Russia. With the development of uranium mining and applications of nuclear technology in recent decades, the radioactive hazards posed by 210Po to living organisms and the environment have become increasingly prominent. In order to strengthen the monitoring of environmental 210Po and protect both the environment and human health, a series of explorations on the methods of 210Po determination have been ongoing by researchers across the globe. However, previous reviews have focused on individual sample types and have not provided a comprehensive account of environmental, food, and biological samples that are closely related to human health. In this work, the sources, health hazards, chemical purification, and detection methods of trace 210Po in different sample types are systematically reviewed. In particular, the advantages and disadvantages of various pretreatment methods are compared, and relevant domestic and international standards are integrated, which puts forward a new direction for the subsequent establishment of rapid, simple, and efficient measurement methods.

Study of Polonium (210Po) Activity Concentration in Fruit Wines Derived from Different Locations in Poland.

This study aimed at assessing the activity concentration and the annual effective dose of polonium-210 (210Po) in fruit wines derived from four locations in Poland (Warmian−Masurian, Podlaskie, Lubelskie and Malopolskie voivodeships). The fruit wines differed significantly (p < 0.05) in 210Po activity depending on the production site, with the Malopolskie site having the highest activity (61.4−221.4 mBq/L) and the Podlaskie having the lowest (3.5−97.1 mBq/L). The site differentiation was due to environmental conditions­soil parameters (uranium concentration), precipitations and terrain characteristics, e.g., the proximity of the lakes. The increased activity concentration of 210Po in samples from Malopolska compared with the other sites probably derived from the environment polluted with aqueous wastes and particulate air pollution. The annual effective dose due to the ingestion of fruit wines ranged from 0.112 to 1.214 µSv/year. These levels of exposure are safe according to the WHO criterion (0.1 mSv per year for ingestion) and to the IAEA reference level for public exposure including food (1 mSv per year). Summing up, the data obtained provide information on the activity concentration of 210Po in fruit wines and increase databases on the natural radioactivity of foodstuffs. Future work is needed to examine 210Po activity in samples from all vineyard regions in Poland.

Hydrogen bonding with polonium.

Hydrogen bonding (H-bonding) with heavier chalcogens such as polonium and tellurium is almost unexplored owing to their lower electronegativities, providing us an opportunity to delve into the uncharted territory of X-H⋯Po/Te H-bonds (X-H, X = O, N, C). Employing high-level quantum mechanical calculations that include dispersion correction and the relativistic effect and considering dimethyl polonium (Me2Po) as the model H-bond donor, we have provided evidence of the X-H⋯Po H-bonds for the first time. The H-bond energies can be as much as 30 kJ mol-1, which is energetically comparable to any conventional H-bonds. It is counterintuitive from the perspective of low electronegativity of polonium but possible if one considers the contributions from polarizability, dispersion, and the relativistic effect. We strongly believe that these fundamental studies are expected to impact polonium chemistry, such as in marine science, as dimethyl polonium is one of the major chemicals produced by aerobic marine microorganisms and tracer applications of polonium for environmental carbon cycles.

Environmental evaluation of radioactivity levels and associated radiation hazards in groundwater around the WIPP site.

Groundwater may contain radioactive substances which can be dangerous to human health. Concentrations of natural radionuclides polonium (Po), thorium (Th), uranium (U), and radium (Ra) isotopes were measured in groundwater samples collected from different locations in the vicinity of the Waste Isolation Pilot Plant (WIPP) site in Carlsbad, New Mexico. The average values of gross activity concentrations of 210Po, 228Th, 238U, 234U, 226Ra and 228 Ra isotopes were determined to be 1.62 Bq L-1 in shallow groundwater and 5.88 Bq L-1 in deep groundwater, respectively. The total radioactivity in deep groundwater was higher than that in shallow groundwater, and most of the radioactivity in the water is from 226Ra. Furthermore, the effective doses for ingestion of natural radionuclides were about 0.333 mSv y-1 for shallow groundwater and about 1.338 mSv y-1 for deep groundwater samples, which are higher than the World Health Organization (WHO, 2017) guideline level (0.1 mSv y-1) for drinking water. Ra dominated the total ingestion dose, contributing 93.06 % and 75.40 % of the total effective doses to the deep and shallow groundwater, respectively. The ingrowth and decay of natural radionuclides suggested that 228Ra/226Ra ratio can be a useful indicator of the source of radioactive contamination. The radioactivity data obtained from the investigated groundwater samples can be used to establish a baseline for radioactivity levels in groundwater around the WIPP site.

Estimation of the Annual Effective Dose Due to the Ingestion of 210Pb and 210Po in Crops from a Site of Coal Mining and Processing in Southwest China.

The exploitation of mineral resources may cause the environmental release of radionuclides and their introduction in the human trophic chain, affecting public health in the short and long term. A case study of the environmental radiation impact from coal mining and germanium processing was carried out in southwest China. The coal mines contain germanium and uranium and have been exploited for more than 40 years. The farmlands around the site of the coal mining and germanium processing have been contaminated by the solid waste and mine water to some extent since then. Samples of crops were collected from contaminated farmlands in the research area. The research area covers a radius of 5 km, in which there are two coal mines. 210Pb and 210Po were analyzed as the key radionuclides during the monitoring program. The average activity concentrations of 210Pb and 210Po in the crops were 1.38 and 1.32 Bq/kg in cereals, 4.07 and 2.19 Bq/kg in leafy vegetables and 1.63 and 1.32 Bq/kg in root vegetables. The annual effective doses due to the ingestion of 210Pb and 210Po in consumed crops were estimated for adult residents living in the research area. The average annual effective dose was 0.336 mSv/a, the minimum was 0.171 mSv/a and the maximum was 0.948 mSv/a. The results show that the crops grown on contaminated farmland contained an enhanced level of radioactivity concentration. The ingestion doses of local residents in the research area were significantly higher than the average level of 0.112 mSv/a in China, and the world average level of 0.042 mSv/a through 210Pb and 210Po in crop intake, respectively.

210Pb and 210Po concentration levels in tobacco products and resulting radiation dose for Egyptian smokers.

The activity concentrations of 210Pb and 210Po in the most popular cigarettes and moassel tobacco brands consumed in Egypt were determined by the spontaneous deposition method using alpha spectrometry. It turned out that the activity concentration of 210Po was higher than that of 210Pb in all tobacco brands. Higher activity concentrations for both 210Pb and 210Po were found in cigarette than in moassel tobacco. The average activity concentrations of 210Pb and 210Po in cigarette tobacco were 11.79 ± 1.67 and 15.00 ± 1.83 mBq cig-1, respectively, whereas in moassel tobacco the values were 7.08 ± 1.91 and 9.12 ± 1.12 mBq g-1, respectively. The daily activities inhaled in the lung of a smoker and the inhalation effective doses due to cigarette and shisha smoking were calculated. The results revealed that the total 210Pb and 210Po daily activities inhaled and the total annual inhalation effective doses due to shisha smoking were two times greater than the corresponding values due to cigarette smoking. Also, the results indicated that the annual effective doses from inhalation of 210Pb and 210Po due to smoking 20 cigarettes per day are 14 and 16 times greater than the annual ingestion doses from the diet, respectively. In contrast, the annual effective doses from inhalation of 210Pb and 210Po due to shisha smoking (27 g moassel tobacco per day) are 26 and 33 times greater than the annual ingestion doses from the diet, respectively.

Occurrence and Geochemistry of Lead-210 and Polonium-210 Radionuclides in Public-Drinking-Water Supplies from Principal Aquifers of the United States.

On the basis of lifetime cancer risks, lead-210 (210Pb) and polonium-210 (210Po) ≥ 1.0 and 0.7 pCi/L (picocuries per liter), respectively, in drinking-water supplies may pose human-health concerns. 210Pb and 210Po were detected at concentrations greater than these thresholds at 3.7 and 1.5%, respectively, of filtered untreated groundwater samples from 1263 public-supply wells in 19 principal aquifers across the United States. Nationally, 72% of samples with radon-222 (222Rn) concentrations > 4000 pCi/L had 210Pb ≥ 1.0 pCi/L. 210Pb is mobilized by alpha recoil associated with the decay of 222Rn and short-lived progeny. 210Pb concentrations ≥ 1.0 pCi/L occurred most frequently where acidic groundwaters inhibited 210Pb readsorption (felsic-crystalline rocks) and where reducing alkaline conditions favored dissolution of iron-manganese- (Fe-Mn-) oxyhydroxides (which adsorb 210Pb) and formation of lead-carbonate complexes (enhancing lead (Pb) mobility). 210Po concentrations ≥ 0.7 pCi/L occurred almost exclusively in confined Coastal Plain aquifers where old (low percent-modern carbon-14) groundwaters were reducing, with high pH (>7.5) and high sodium/chloride (Na/Cl) ratios resulting from cation exchange. In high-pH environments, aqueous polonium (Po) is poorly sorbed, occurring as dihydrogen polonate (H2PoO3(aq)) or, under strongly reducing conditions, as a hydrogen-polonide anion (HPo-). Fe-Mn- and sulfate-reduction and cation-exchange processes may mobilize polonium from mineral surfaces. Po2+ occurrence in low-to-neutral-pH waters is attenuated by adsorption.

The activities of 210Po and 210Pb in cigarette smoked in Tunisia.

In this study, the activity concentration of polonium 210 in cigarette for Tunisian consumers was investigated by alpha spectrometry. After chemical digestion of tobacco, 210Po was extracted, auto-deposited on disc and measured. The activity of 210Pb was assessed after radioactive equilibrium was achieved. The activity levels of 210Po ranged between 7.8 ± 0.3 and 17 ± 0.5 mBq per cigarette with an average of 12.9 ± 0.4 mBq per cigarette. Effective doses per year due to cigarette smoking were calculated assuming that 22% of the 210Pb and 210Po in tobacco were retained in the lungs of the smokers. It is concluded that for a smoker in Tunisia, the average effective dose is about 90.6 ± 3.3 µSv per year for a cigarette consumption of one pack of cigarettes per day. This value is somewhat lower than 106.4 ± 5.3 µSv per year estimated as the mean global effective dose from smoking.

Determination and distribution of 210Po in different morphological parts of tobacco plants and radiation dose assessment from cigarettes in Turkey.

Both sides of tobacco leaves accumulate 210Po through their sticky hairs (trichomes) by means of diffusive deposition. It is known that tobacco leaves may contain high amounts of 210Po concentrations. However, there is less information about radionuclides in tobacco plants. In the study, the 210Po concentrations were determined monthly in different morphological parts of tobacco plants (leaf, stem, root) and soil samples and soil-to-plant transfer factor for 210Po was determined and the activity concentrations of 210Po radionuclide in 16 different popular brands of cigarettes were investigated in order to estimate the annual effective doses of 210Po to smokers. Besides the study investigated (focused on) the correlation between the amount of rainfall and 210Po concentration of tobacco leaf. The results of the present study indicated that the activity concentration of 210Po in cigarettes distributed in Turkey ranged from 16.1 ± 1.0 to 37.6 ± 2.6 mBq per cigarette and the mean value of their activity concentrations was 22.4 ± 1.5 mBq per cigarette. The mean value of annual effective doses of 210Po to smokers (20 cigarettes smoked by an individual per day) obtained from these activity concentrations was estimated to be 188.5 ± 12.4 µSv y-1.

Activity concentrations of 210Po and 210Pb in fish and mussels in Izmir, Turkey, and the related health risk assessment (dose assessment and pesticide levels) to the consumers.

The activity concentrations of natural radionuclides (210Po and 210Pb) and residual pesticide levels were determined from the fish (red mullet, common sole, anchovy, horse mackerel, gray mullet, and sardine) and mussel samples collected in Izmir Bay seasonally from October 2012 and July 2013. The 210Po and 210Pb concentrations varied between 5.7 ± 4.0 Bq kg-1 dry weight (dw) to 353.7 ± 45.0 Bq kg-1(dw) and 0.7 ± 0.2 Bq kg-1 (dw) to 4.3 ± 0.8 Bq kg-1 (dw), respectively. From a public health point of view, the fish and mussel collected from the Izmir Bay are not harmful to consumers.

Human Exposure to Radioactivity From Tobacco Smoke: Systematic Review.

INTRODUCTION: Tobacco has been known to contain radioactive polonium and lead for 50 years but the literature is divided as to the public health significance. I review the data on tobacco radioactivity and its internalization by smokers. METHODS: Data sources: Reports of lead-210 and polonium-210 content of tobacco leaf, cigarettes, cigarette smoke, and human respiratory tissues, published between 1964 and September 2017. Study selection: Any identified study that reported values for lead-210 and polonium-210 content. Data extraction: Data quality was addressed by comparative review of analytic methods. RESULTS: The data about radiation content of tobacco and smoke are robust. Early reports suggesting microsievert lifetime doses of inhaled radioactivity to smokers were not borne out. The results remain sensitive to pharmacological assumptions around absorption and redistribution of inhaled radionuclides, and radiobiological assumptions about interaction with human tissues. CONCLUSIONS: Literature on tobacco radioactivity has not fully contended with pharmacological and radiobiological uncertainty, and is therefore divided as to health significance. This does much to explain regulatory inaction over the last half century. Before radiation safety law can offer a vehicle for tobacco control, more must be learnt about the pharmacology and radiobiology of inhaled radionuclides in tobacco smoke. IMPLICATIONS: This work makes it apparent that the study of tobacco smoke radioactivity has been scientifically stagnant for the last 40 years. The field cannot advance until we improve understanding of the pharmacology and radiobiology of inhaled radionuclides in tobacco smoke. Despite this, a subset of contemporary authors is still suggesting individual health risks about 1000 times higher than can be supported by internationally accepted models.

Comparison of 238U, 210Po and 210Pb Speciation in Six Different Types of Soils.

Speciation of 238U, 210Po and 210Pb in six different types of Syrian soil (Entisols, Inceptisol, Aridisol, Mollisols, Vertisols and Rock outcrops) was studied using a four-step sequential extraction procedure. The binding nature of 238U, 210Po and 210Pb was correlated with soil properties including soil particles, pH, EC, OM, sand, silt and clay. The results showed that the exchangeable and carbonate fractions of 238U did not exceed 10%. In addition, the 238U, 210Po and 210Pb fractions bonded to organic matter increased as the soil clay content decreased. The highest 210Po fraction was found to be bonded to soil Fe/Al/Mn-oxides for Entisols soils (56%) and silica for Aridisol soils (53%). Soil clay content showed a linear correlation with 210Po concentrations in soils ranging from 0.34 to 0.91. The results are considered useful in assessing the risks resulting from soils contaminated by naturally occurring radioactive material from the phosphate and oil industry.

Natural levels of polonium-210 in urine.

This paper presents a review and analysis of available data on background levels of polonium-210 in urine. It was established that 819 measurements could be considered to correspond to natural background levels, excluding a large number of values identified by the original investigators as potentially due to an artificial source or due to recognised enhancement of dietary intake. Almost 550 measurements were extracted from studies reported in the literature; additional measurements were contributions of previously unpublished data by authors of more recent papers. The majority of the measurements (462) were single samples from individuals but 357 values were repeat measurements provided by 81 subjects and for these the mean value for each subject was used. The final dataset consisted of measurements from 543 individuals. Analysis of the measurements confirmed the data was log normally distributed with mean and median values of 15.5 mBq d-1 and 11 mBq d-1 in urine samples, respectively. While the overall range was from 0.3-111 mBq d-1, almost 90% of the measurements were less than 30 mBq d-1, 95% were less than 45 mBq d-1, and 99% less than 70 mBq d-1. Separate analysis of data for smokers and non-smokers suggested a modest increase in smokers of up to 5 mBq d-1. Perhaps reflecting the importance of dietary differences such as seafood consumption, a marked difference between countries was observed in the range of results. While for most countries, 95% or more of results were below 30 mBq d-1, China and Italy were notable exceptions, with greater than 20% of values above this level.

Studying of 210Po and 210Pb Deposition in Some Lichen Species in Manisa, Turkey.

Lichens are very useful for monitoring of the radionuclide deposition because having a high efficiency capturing the radionuclides from the atmospheric fallout. In the present work, 210Po and 210Pb deposition in some lichen species were determined using an alpha spectrometer. Different lichens were collected around Demirci-Manisa and investigated their uses as biomonitor for 210Po and 210Pb deposition. The highest activity concentrations for 210Po and 210Pb were detected in Neofuscelia pulla (898 Bq kg-1 and 1207 Bq kg-1, respectively). The mean activities in the lichen species ranged from 164 to 584 Bq kg-1 for 210Po and from 175 to 671 Bq kg-1 for 210Pb. The activity ratios for 210Po/210Pb ranged from 0.75 to 1.57.

Polonium-210 poisoning: a first-hand account.

BACKGROUND: Polonium-210 ((210)Po) gained widespread notoriety after the poisoning and subsequent death of Mr Alexander Litvinenko in London, UK, in 2006. Exposure to (210)Po resulted initially in a clinical course that was indistinguishable from infection or exposure to chemical toxins, such as thallium. METHODS: A 43-year-old man presented to his local hospital with acute abdominal pain, diarrhoea, and vomiting, and was admitted to the hospital because of dehydration and persistent gastrointestinal symptoms. He was initially diagnosed with gastroenteritis and treated with antibiotics. Clostridium difficile toxin was subsequently detected in his stools, which is when he first raised the possibility of being poisoned and revealed his background and former identity, having been admitted under a new identity with which he had been provided on being granted asylum in the UK. Within 6 days, the patient had developed thrombocytopenia and neutropenia, which was initially thought to be drug induced. By 2 weeks, in addition to bone marrow failure, he had evidence of alopecia and mucositis. Thallium poisoning was suspected and investigated but ultimately dismissed because blood levels of thallium, although raised, were lower than toxic concentrations. The patient continued to deteriorate and within 3 weeks had developed multiple organ failure requiring ventilation, haemofiltration, and cardiac support, associated with a drop in consciousness. On the 23rd day after he first became ill, he suffered a pulseless electrical activity cardiorespiratory arrest from which he could not be resuscitated and was pronounced dead. FINDINGS: Urine analysis using gamma-ray spectroscopy on day 22 showed a characteristic 803 keV photon emission, raising the possibility of (210)Po poisoning. Results of confirmatory analysis that became available after the patient's death established the presence of (210)Po at concentrations about 10(9)-times higher than normal background levels. Post-mortem tissue analyses showed autolysis and retention of (210)Po at lethal doses in several organs. On the basis of the measured amounts and tissue distribution of (210)Po, it was estimated that the patient had ingested several 1000 million becquerels (a few GBq), probably as a soluble salt (eg, chloride), which delivered very high and fatal radiation doses over a period of a few days. INTERPRETATION: Early symptoms of (210)Po poisoning are indistinguishable from those of a wide range of chemical toxins. Hence, the diagnosis can be delayed and even missed without a high degree of suspicion. Although body surface scanning with a standard Geiger counter was unable to detect the radiation emitted by (210)Po, an atypical clinical course prompted active consideration of poisoning with radioactive material, with the diagnosis ultimately being made with gamma-ray spectroscopy of a urine sample. FUNDING: UK NHS, Public Health England, and the UK Department of Health.