Radioactivity of cigarettes and the importance of (210)Po and thorium isotopes for radiation dose assessment due to smoking

Determination of activities of 210Pb in Slovak tobacco and cigarettes: a study on radiological risks

This study investigates the 210Pb activity concentrations in tobacco and cigarettes available in Slovakia, utilizing two specific extraction methods including the Sr Resin sorbent used in extraction chromatography, and the AnaLig Sr01 sorbent, which operates based on molecular recognition principles. The findings revealed significant variations in 210Pb activity concentrations, with concentrations ranging from 13.3 to 33.8 mBq/g in tobacco, and from 16.8 to 28.5 mBq/g in cigarettes. The average 210Pb activity per cigarette was 14.4 mBq ± 1.7 mBq. Annual effective doses for smokers were calculated, with values for tobacco ranging from 27.9 to 126.7 µSv and for cigarettes from 25.5 to 115.7 µSv. The study highlights the importance of comparing these two methods to ensure an accurate assessment of 210Pb exposure and evaluation of radiological risks associated with smoking in Slovakia.

New insights in tobacco radiotoxicity: on the research of 210Po in modern heated tobacco product-radioactivity, distribution, and dose assessment

The purpose of the study was to assess the radiological risk to users and the environment related to the Glo system used to heat tobacco. The concentration of 210Po, radioactivity per cartridge, and radiation dose assessment were evaluated. For comparison purposes, to present the exposure scale, the same analyses were also performed for several traditional cigarettes. The tests were carried out on an alpha spectrometer equipped with a PIPS detector. After examining 60 samples, the concentration of 210Po was found in tobacco that was a filling of Neo cartridges and in traditional cigarettes. 210Po concentrations [in mBq∙g-1] in heated tobacco were higher than in unheated. After heating, a little release of polonium (mBq per cartridge) was observed. The research was also done taking into account the flavor of the Neo cartridges and cartridges from different packages. The 210Po concentrations in heated Neo cartridges were greater than 30 mBq∙g-1 and in traditional cigarettes up to 50 mBq∙g-1. The estimated annual effective dose for Neo cartridges was lower than that for traditional smoking. However, it cannot be concluded that the use of Neo cartridges is healthier and does not affect the environment. What is disturbing is the increase in the number of cartridges used daily, resulting in the creation of waste containing 210Po and, of course, a higher effective dose received by the user.

Psychological Therapies Used for the Reduction of Habitual Cigarette Smoking Cigarette Consumption: A Systematic Review

Globally, there are around 1.3 billion cigarette consumers, indicating it to be the second highest risk factor for early death and morbidity. Meanwhile, psychological therapy offers tools based on its different models and techniques, which can contribute to smoking cessation. In this context, this study gathers scientific evidence to identify psychological therapies that can be used to reduce cigarette consumption. A systematic review of controlled clinical studies was conducted, implementing the PRISMA methodology. Search queries were performed with terms extracted from MESH (Medical Subject Headings) and DECS (Descriptors in Health Sciences). Subsequently, the search was queried in the scientific databases of Medline/PubMed, Cochrane, Scopus, Science Direct, ProQuest, and PsycNet, with subsequent verification of methodological quality using the Joanna Briggs Institute checklists. The selected documents revealed that cognitive behavioral therapy prevails due to its use and effectiveness in seven publications (25%). The cognitive approach with mindfulness therapy is found in 4 publications (14%), the transtheoretical model with motivational therapy in 4 publications (14%), brief psychological therapy in 3 publications (10%), and the remaining 10 documents (37%) correspond with others. Intervention studies refer to cognitive behavioral therapy as the most used in reducing cigarette consumption; in terms of the duration of abstinence, scientific evidence shows beneficial effects with short-term reduction.

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 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.

Review of natural radioactivity in tobacco cigarette brands

Cigarettes smoking are leading causes of lung cancer in the world. In several countries, the radioactivity of tobaccos cigarette brands has been evaluated to estimate the effective dose from smoking inhalation. In this paper, we have reviewed 40 researched papers of radioactivity in tobacco cigarette brands by searching specified databases from various search engines such as Web of Science, Google Scholar, Scopus, Science Direct and PubMed for the studies published between the year 2000 and November, 2023 in English language. Results show that, the arithmetic mean and range of radioactivity concentration in mBq/g were 20.4 (0.4-128.6), 15.4 (2.0-78.8), 630.8 (1.2-1330.0), 8.1 (0.3-41.0), 15.2 (0.2-82.0) and 5.9 (2.0-16.0) from 210Po, 210Pb, 40K, 232Th and 232U and 226Ra, respectively. The annual effective doses were also estimated using the assumption that a smoker smokes 20 cigarettes per day. The mean annual effective doses in μSv/y from 210Po, 210Pb, 40K, 232Th and 232U and 226Ra were 295, 74.1, 5.80, 889.7, 192.6 and 90.1, respectively. The mean annual effective dose is lower than the reference level 1000 to 20000 μSv/y for existing situation in ICRP Publication 103. The average value of ELCR is 1.03 ×10-3, 0.26 ×10-3,0.02 ×10-3,3.11 ×10-3,0.67 ×10-3 and 0.32 ×10-3 for 210Po, 210Pb, 40K, 232Th and 232U and 226Ra, respectively. The ELCR values obtained in this study are well below the world average value of 1.45 ×10-3. The mean value of LCC in per million is 5.3, 1.3, 0.1, 16, 3.5 and 1.6 for 210Po, 210Pb, 40K, 232Th and 232U and 226Ra, respectively. The values of LCC obtained in this study are all below the limit range of 170-230 per million persons. The result shows 232Th contribute much larger for annual effective dose, annual equivalent dose, ELCR and LCC for smoking tobacco cigarette brands compared to other radionuclides. More studies in radioactivity in tobacco cigarette brands from different countries are required to have conclusive mean annual effective dose, annual equivalent dose, ELCR and LCC for each natural radionuclide.

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.

Dosimetry in the lungs of α-particles (210Po) and β-particles (210Pb) present in the tobacco smoke of conventional cigarettes and heated tobacco products

Tobacco products contain radioactive ²¹⁰Pb and ²¹⁰Po which can be transferred from the filler to the mainstream smoke. When inhaled, they can contribute to the radioactive dose to the lungs and are suspected to significantly contribute to lung cancer from smoking. Currently, no data are available on the radioactive risk of the heated tobacco products (HTP). However, due to the relatively high heat involved in some of these devices, there are concerns about the volatility of polonium particles. Here we used data on the ²¹⁰Po and ²¹⁰Pb content in tobacco smoke along with biokinetic and dosimetric models to compute the effective dose induced by conventional smoking and by using an HTP device (PMI IQOS system). Results show that conventional smoking of one pack per day induces a dose to the lung of about 0.3 mSv/year. This dose decreases by a factor of ten (0.03 mSv/year) for the IQOS system. However, this dose reduction is not obtained by specific countermeasures but by the fact that the IQOS system heats only 15% of the tobacco filler to the target temperature of 330 °C. When heated homogeneously to 300 °C, both conventional and Heets (IQOS) cigarettes release about 80% of the ²¹⁰Po from the tobacco, leading to similar doses to lungs.

Radiation doses due to smoking different types of tobacco leaves grown in Turkey

The activity concentrations of 238U, 232Th, 40 K and 137Cs radionuclides in 25 samples of tobacco leaves grown in Turkey have been measured using a high purity co-axial germanium detector. The measured activity concentrations for 238U ranged from 3.6 to 22.5 Bq kg-1 with an average of 9.8 Bq kg-1, for 232Th from 0.8 to 11.0 Bq kg-1 with an average of 2.4 Bq kg-1, and for 40 K from 360.3 to 1,479.5 Bq kg-1 with an average of 810.0 Bq kg-1. The concentrations of 137Cs, the residue of fallout from the Chernobyl reactor accident, were found to range from 0.2 to 2.1 Bq kg-1 with an average of 0.5 Bq kg-1. The results indicate that the average activity concentrations of 238U and 232Th lie within the range of measured values worldwide, whereas for 40 K the average was found to be higher. The average annual effective radiation doses from the inhalation of the corresponding tobacco smoke by an adult smoking 20 cigarettes per day was deduced to be 93.3 μSv y-1 for 238U, 193.2 μSv y-1 for 232Th, 5.6 μSv y-1 for 40 K, and 292.1 μSv y-1 in total. The average annual effective dose from 137Cs was calculated to be 8.5 nSv y-1. The resulting average annual effective radiation doses of 0.3 mSv due to the inhalation of natural radiation sources in tobacco were compared with studies worldwide and found much smaller than the worldwide average effective dose of 1.26 mSv. It is concluded that smoking may contribute a non-negligible fraction to the annual effective dose depending on cigarette consumption and activity concentration in tobacco. This study is the first in which natural and anthropogenic radioactivity in tobacco in Turkey was measured. Therefore, it is considered as a baseline study. Further studies are needed to investigate the role of tobacco refinement in the observed reduction of 238U concentration of refined tobacco.

Soil to tobacco component transfer factors for natural radionuclides 40K, 226Ra, and 232Th and the risk assessment of tobacco leaf in smoking

This study determined the activity concentrations and corresponding transfer factors (TF) of ⁴⁰K, ²²⁶Ra, and ²³²Th in three tobacco components (root, stem, and leaf). The radiation hazard index parameters were assessed for the tobacco leaf. The activity concentrations in the soil were 589-762, 32-43, and 49-59 Bq kg-dw^-1 (dry weight) for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively. The average activity concentrations of ⁴⁰K, ²²⁶Ra, and ²³²Th were 447, 5.41 and 5.69 Bq/kg-dw for the root, 670, 9.64 and 7.61 Bq kg-dw^-1 for the stem, and 793, 6.79 and 6.15 Bq kg-dw^-1 for the leaf, respectively. The TF values were 0.42-1.42, 0.10-0.49 and 0.06-0.23 for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively. The stem and leaf ⁴⁰K TF values were significantly higher than the root values. The stem ²²⁶Ra TF values were significantly higher than the root values. The ²²⁶Ra and ²³²Th activity concentrations and TFs of tobacco components had a significant positive correlation. Based on the activity concentrations of the tobacco leaves, the annual inhalation effective dose to the lungs for an adult smoker was 0.32-0.81 mSv y^-1 (average 0.60 mSv y^-1). The Excess Lifetime Cancer Risk (ELCR) caused by smoking was an average of 2.39 × 10^-3.

210Po and 210Pb content in the smoke of Heated Tobacco Products versus Conventional Cigarette smoking

210Po is a radioactive component of conventional cigarette tobacco smoke and is a recognized carcinogen. Despite the expanding market of heated tobacco products, no data are available on the activity of 210Po in the smoke of IQOS Heets cigarette. We determined the 210Po activity in the mainstream smoke of thirteen cigarette brands available on the Swiss market using a smoking machine and compared the results to the 210Po activity measured in the mainstream smoke of the IQOS system. In addition, we measured the 210Po and 210Pb loss on heating after uniform heating from 50 to 600 °C for several cigarette brands and the Heets cigarettes. 13.6 ± 4.1% of 210Po activity was found in the mainstream smoke in conventional cigarette smoking (7% for 210Pb). This dropped to 1.8 ± 0.3% in the mainstream smoke of IQOS Heets. Conversely, when the tobacco was heated uniformly at 330 °C, a loss of 210Po of more than 80% was observed for all type of cigarettes. Apparently, IQOS significantly reduced the 210Po and 210Pb activities in the mainstream smoke. However, our results show that only 15% of the Heets tobacco reaches 330 °C with IQOS. While IQOS reduces the 210Po and 210Pb activities in the mainstream smoke compared to conventional cigarettes, it only heats a marginal fraction of the tobacco present in the Heets cigarette. Because smoking is an addiction (mostly due to nicotine), IQOS could possibly deliver an unsatisfactory dose of nicotine to a Heets cigarette smoker, as most of the tobacco is left unaltered.

Thorium and fetal neural tube defects: an epidemiological evidence from large case-control study

Background

Thorium is ubiquitous in the environment and its relationship with birth defects is still under discussion. This study aimed to investigate the associations of maternal exposure to thorium with risk of neural tube defects (NTDs) by using a case–control study, as well as the relationship between thorium exposure and the indoor air pollution from coal combustion.

Methods

This study was conducted in 11 local healthcare hospitals during 2003–2007 in Shanxi and Hebei provinces, China. A total of 774 mothers were included as participants who delivering 263 fetuses with NTDs including 123 with anencephaly, 115 with spina bifida, 18 with encephalocele, and 7 other NTD subtypes (cases), and 511 health fetuses without NTDs (controls). Their hair samples were collected as close as to the occipital posterior scalp, of which those grew from 3 months before to 3 months after conception was cut to measure the thorium concentration by inductively coupled plasma-mass spectrometry.

Results

We found a higher hair thorium concentration in the total NTD cases with 0.901 (0.588–1.382) ng/g hair [median (inter-quartile range)] than that in the controls with a value of 0.621 (0.334–1.058) ng/g hair. Similar results were found for the three concerned NTD subtypes. Maternal hair thorium concentration above its median of the controls was associated with an increased risk of the total NTDs with an adjusted odds ratio of 1.80 [95% confidence interval (CI), 1.23–2.63)] by adjusting for all confounders. There was obvious dose-response relationship between maternal hair thorium concentration and the risk of total NTDs, as well as their two subtypes (i.e. anencephaly and spina bifida). Maternal hair thorium concentration was positive associated with their exposure level to indoor air pollution from coal combustion during cooking.

Conclusions

Overall, our findings revealed that maternal periconceptional thorium exposure was associated with the risk of NTDs in North China. Reducing the coal usage in the household cooking activities may decrease maternal thorium exposure level.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s41021-021-00227-w.

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.

Transfer and bioaccumulation of 210Po from soil to water spinach (Ipomoea aquatica Forrsk.) in Vietnam

The water spinach (Ipomoea aquatica Forrsk.) is a common vegetable and a part of the staple diet in Vietnam. It has a well-known tendency for the high absorption of lead, including the radioactive isotope ²¹⁰Pb. ²¹⁰ Pb day to ²¹⁰Po, which is one of the most toxic radioactive isotopes when ingested. Currently, there are few data available on the activity concentration or transfer parameters of water spinach grown in Vietnam. To provide this data, in this study, the ²¹⁰Po activity concentrations in the soil, water and the roots, stems, and leaves of two types of spinach (grown in soil flooded with water and grown in normal soil) in Hanoi, Vietnam were determined by alpha spectrometry. The order of activity concentrations for water spinach grown in unflooded was C_stem < C_leaf < C_root, while for flooded C_stem ≈ C_root < C_leaf. The transfer factors followed a similar pattern.

210PO IN SOIL AND TOBACCO LEAVES IN QUANG XUONG, VIETNAM AND ESTIMATION OF ANNUAL EFFECTIVE DOSE TO SMOKERS

210Po is the main radiotoxic chemical in tobacco smoke and one of the primary causes of lung cancer. Investigating 210Po concentration in tobacco is important in estimating the annual effective dose (AED) due to smoking. In this study, the 210Po concentrations in tobacco leaves and soil in Quang Xuong, Vietnam were measured using a high-resolution passivated and implanted planar silicon detector. Based on these data the AEDs to smokers were estimated. The 210Po activity concentration in tobacco varied significantly from 28.7 to 254.0 mBq g-1, whereas its variation in soil was insignificant. The AED due to smoking fresh tobacco leaves in Vietnam (average 565 μSv y-1) was significantly higher than the values reported for other countries (36-361 μSv y-1).

STUDY OF POLONIUM-210 IN PERSIAN CIGARETTE AND TOBACCO CROPS

Alpha radiation from Polonium-210 (210Po) is considered to be an important agent of bronchial cancer in smokers. Besides reexamination of the radionuclide in domestic and imported cigarette brands separately, the radioactive contamination was also followed during the cigarette-producing procedure in Gilan as one of the major regions of tobacco cultivation in Iran. The activity level of 210Po in Iranian domestic and imported cigarettes averaged 38.4 ± 6% and 20.0 ± 7% mBq g-1, respectively. Drying in direct contact with fumes of fossil fuel seems like one of the main excessive sources of 210Po in Persian cigarettes.

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.

Determination of Po-210 content in cigarette smoke using a smoking machine: A case study of Iranian cigarettes

The Po-210 content of tobacco has been known for a long time, however, different results can be found about the estimated amount of Po-210 that is inhaled by humans as a result of smoking cigarettes. Because of the unique properties of Po-210, the smoking machines available on the market are not suitable because of their failure to quantitatively collect Po-210 for measurement. Therefore, to estimate precisely the amount of Po-210 entering the lungs as a result of smoking, a smoking machine and sampling protocol based on relevant ISO standards - ISO-3308, ISO-3402 and ISO-4387 - was developed. A 5% HCl solution was found to be the best absorber of Po-210 from smoke. Seventeen different brands of cigarettes distributed in Iran were used to validate the new machine and sampling protocol. The Po-210 concentration was determined by alpha spectrometry; the cigarette smoke solution underwent combined acid treatment after adding a Po-209 tracer. The Po-210 activity concentration of cigarettes sold in Iran was between 9.7 ± 1.2 and 26.5 ± 4.6 mBq/cigarette and it was determined that there was no relationship between the Po-210 and nicotine contents of cigarette smoke. Additionally, it was found that 15 ± 10% of the cigarette Po-210 was transferred to the mainstream smoke.