Concentrations of 210Pb and 210Po in human soft tissues

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.

Radiation doses to members of the U.S. population from ubiquitous radionuclides in the body: Part 3, results, variability, and uncertainty

This paper is Part 3 of a three-part series investigating effective dose rates to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. The radionuclides of interest are the (238)U series (14 nuclides), the actinium series (headed by (235)U; 11 nuclides), and the (232)Th series (11 nuclides); primordial radionuclides (87)Rb and (40)K; cosmogenic and fallout radionuclides (14)C and (3)H; and purely anthropogenic radionuclides (137)Cs-(137m)Ba, (129)I and (90)Sr-(90)Y. This series of papers explicitly excludes intakes from inhaling (222)Rn, (220)Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. In this work, it is assumed that instantaneous dose rates in target organs are proportional to steady-state radionuclide concentrations in source regions. Part 1 reviewed, summarized, characterized, and grouped all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Part 2 described the methods used to organize the data collected in Part 1 and segregate it into the ages and genders defined by the study, including imputed missing values from the existing data, apportioned activity in bone, and imputed activity in hollow organ contents and the remainder of the body. This paper estimates equivalent dose rates to target tissues from source regions and maps target tissues to lists of tissues with International Commission on Radiation Protection (ICRP) tissue-weighting factors or to surrogate tissue regions when there is no direct match. Effective dose rates using ICRP tissue-weighting factors recommended in 1977, 1990, and 2007, are then calculated, and an upper bound of variability of the effective dose rate is estimated by calculating the average coefficients of variation (CV), assuming all variance is due to variability. Most of the data were for adult males, whose average effective dose rate is estimated to be 337 μSv y(-1) (CV = 0.65, geometric mean = 283 μSv y(-1), geometric standard deviation s(G) = 1.81) using 2007 ICRP tissue-weighting factors. This result is between the National Council on Radiation Protection and Measurements' 1987 estimate of 390 μSv y(-1) (using 1977 w(T)s) and its 2009 estimate of 285 μSv y(-1) (using 2007 w(T)s) and is higher than the United Nations Scientific Committee on the Effects of Atomic Radiation's 2000 estimate of 310 μSv y(-1) (using 1990 w(T)s). The methods and software developed for this project are sufficiently detailed and sufficiently general to be usable with autopsy data from any or all countries.

Radiation doses to members of the U.S. population from ubiquitous radionuclides in the body: Part 1, autopsy and in vivo data

This paper is Part 1 of a three-part series investigating steady-state effective dose rates to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling (222)Rn, (220)Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. In this work, it is assumed that instantaneous dose rates in target organs are proportional to steady-state radionuclide concentrations in source regions. The goal of Part 1 of this work was to review, summarize, and characterize all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Forty-five papers and reports were obtained and their data reviewed, and three data sets were obtained via private communication. The 45 radionuclides of interest are the (238)U series (14 nuclides), the actinium series (headed by (235)U; 11 nuclides), and the (232)Th series (11 nuclides); primordial radionuclides (87)Rb and (40)K; cosmogenic and fallout radionuclides (14)C and (3)H; and purely anthropogenic radionuclides (137)Cs-(137m)Ba, (129)I, and (90)Sr-(90)Y. Measurements judged to be relevant were available for only 15 of these radionuclides: (238)U, (235)U, (234)U, (232)Th, (230)Th, (228)Th, (228)Ra, (226)Ra, (210)Pb, (210)Po, (137)Cs, (87)Rb, (40)K, (14)C, and (3)H. Recent and relevant measurements were not available for (129)I and (90)Sr-(90)Y. A total of 11,741 radionuclide concentration measurements were found in one or more tissues or organs from 14 states. Data on age, gender, geographic locations, height, and weight of subjects were available only sporadically. Too often authors did not provide meaningful values of uncertainty of measurements, so that variability in data sets is confounded with measurement uncertainty. The following papers detail how these shortcomings are overcome to achieve the goals of the three-part series.

210Po 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.

Biological response to nonuniform distributions of (210)Po in multicellular clusters

Radionuclides are distributed nonuniformly in tissue. The present work examined the impact of nonuniformities at the multicellular level on the lethal effects of (210)Po. A three-dimensional (3D) tissue culture model was used wherein V79 cells were labeled with (210)Po-citrate and mixed with unlabeled cells, and multicellular clusters were formed by centrifugation. The labeled cells were located randomly in the cluster to achieve a uniform distribution of radioactivity at the macroscopic level that was nonuniform at the multicellular level. The clusters were maintained at 10.5 degrees C for 72 h to allow alpha-particle decays to accumulate and then dismantled, and the cells were seeded for colony formation. Unlike typical survival curves for alpha particles, two-component exponential dose-response curves were observed for all three labeling conditions. Furthermore, the slopes of the survival curves for 100, 10 and 1% labeling were different. Neither the mean cluster absorbed dose nor a semi-empirical multicellular dosimetry approach could accurately predict the lethal effects of (210)Po-citrate.

Health risk evaluations for ingestion exposure of humans to polonium-210

The incident in London during November 2006 involving a lethal intake by Mr. Alexander Litvinenko of the highly-radioactive, alpha-particles-emitting polonium-210 (Po-210) isotope, presumably via ingestion, sparked renewed interest in the area of Po-210 toxicity to humans. This paper is the result of assembling and interpreting existing Po-210 data within the context of what is considered a reliable risk model (hazard-function [HF] model) for characterizing the risk of death from deterministic effects of high alpha radiation doses and dose rates to body organs. The HF model was developed to address radiation exposure scenarios involving combined exposures to alpha, beta, and gamma radiations and can be used in circumstances where only one type of radiation is involved. Under a plausible but not yet validated set of assumptions and using available megabecquerel (Po-210) to gray dose-conversion factors, acute lethality risk vs. dose curves were developed for circumstances of ingestion exposure to Po-210 by humans. Initial risk calculations were carried out for a reference adult male human (a hypothetical 70-kg person). Results were then modified for application to all ages (except the in utero child) via the use of systemic Po-210 burden. Because of the unavailability of acute lethality data derived from human ingestions of high levels of Po-210, plausibility of risk calculations were evaluated based on data from studies of Po-210 injections in animals. The animal data, although limited, were found to be consistent with the theoretical risk calculations. Key findings are as follows: (1) ingestion (or inhalation) of a few tents of a milligram of Po-210 will likely be fatal to all exposed persons. (2) Lethal intakes are expected to involve fatal damage to the bone marrow which is likely to be compounded by damage caused by higher doses to other organs including the kidneys and liver. (3) Lethal intakes are expected to cause severe damage to the kidney, spleen, stomach, small and large intestines, lymph nodes, skin, and testes (males) in addition to the fatal damage to bone marrow. (4) The time distribution of deaths is expected to depend on the level of radioactivity ingested or inhaled, with deaths occurring within about a month after very high levels of radioactivity intake (e.g., systemic burdens > 1 MBq/kg-body-mass) and occurring over longer periods, possibly up to or exceeding a year for lower but lethal intakes (systemic burdens from 0.1 to 1.0 MBq/kg-body-mass). Below a systemic burden estimate of 0.02 MBq/kg-body-mass, deaths from deterministic effects are not expected to occur but the risk of cancer and for life shortening could be significant. New, funded experimental and modeling/theoretical research is needed to improve on these estimates.

Polonium 210Po in cigarettes produced in Poland

This paper discusses the results of 210Po determinations in the fourteen most frequently smoked brands of cigarettes, which constitute over 80% of total cigarette consumption in Poland. The 210Po activity in the cigarette samples analysed (tobacco, ash, filter before and after smoking) were measured using alpha spectrometry (Canberra-Packard). The data indicates that there is considerable variation in the polonium content of these brands. The highest 210Po content per sample was found in the cheap "Popularne" brand (24.12 mBq), the lowest in "Caro" (4.23 mBq). There was also a large difference between the polonium remaining in the ash in comparison with its total content in the tobacco in all the brands (from 4.3% for "Golden American" to 71.0% for "Sobieski King-Size"). The analysis has demonstrated that filters absorbed only a small amount of the polonium contained in the tobacco. "Caro" cigarettes have the most efficient filter, retaining 25.1% of the polonium contained in the tobacco, but most filters absorbed only 0.1-7.2% of polonium. The daily inhalation of 210Po by Polish smokers who get through one pack per day ranges from 20 to 215 mBq, but people smoking two or more packs of "Popularne" brand will inhale over 430 mBq of polonium per day.

Concentrations of 210Pb and 210Po in hair and urine of workers, of the uranium mine at Poços de Caldas (Brazil)

210Po and 210Pb concentrations in urine and hair samples from individuals working in different areas of the uranium industrial complex of Poços de Caldas (Brazil) have been determined and compared with a control group of occupationally unexposed individuals. In the control group, smokers showed higher urinary excretion of these radionuclides. Such difference could not be detected in the workers group, which showed an increase in urinary excretion of 210Po for the group working in the chemical laboratory. Accumulation of 210Po and 210Pb in hair showed the same trends as for urinary excretion. The workers group, with the exception of the office employees, showed a 210Po/210Pb ratio > 1 in hair.

Cigarette smoking and semen quality in men of reproductive age

The effect of cigarette smoking on conventional semen parameters was studied in voluntary men of reproductive age (n = 190). Special attention was focused on sperm motility and its quantitative and qualitative change in vitro during the observation period. The sperm output war normal in both smokers (n = 54) and non-smokers (n = 110), but semen volume was smaller (p less than 0.03) in heavy smokers (greater than 16 cigarettes/day) than non-smokers. In sperm morphology there was no difference between study groups. The only clear difference between men with different smoking habits was in the percentual change in the sperm motility during 24 hours. At the time of first examination, the sperm motility was better (p less than 0.02) in heavy smokers than those who smoked less than 16 cigarettes per day and the motility decreased more rapidly (p less than 0.007) in heavy smokers than non-smokers. The objectively measured initial mean velocities of the whole sperm population and of the progressive spermatozoa were slightly higher in subgroup of smokers than in non-smokers. The rapid decrease in the survival spermatozoa in smokers may be uneconomical and harmful in respect of fertility.

Testicular function in potential sperm donors: normal ranges and the effects of smoking and varicocele

Testicular exocrine (semen analysis) and endocrine (plasma LH, FSH, prolactin and testosterone) function was assessed in 119 consecutive healthy men presenting for screening as potential sperm donors. Since these volunteers were unbiased with respect to their fertility status, this sample of the general male population was suitable to determine normal ranges and the influence of a variety of physical (height, weight, standardized body weight, varicocele) and demographic (age, marital and fertility status, tobacco and alcohol consumption) factors on normal human testicular endocrine and exocrine function, without the confounding effects of bias in selection of subjects. The statistical distribution of all seminal parameters was non-gaussian, but cube-root transformation of the data normalized the distribution, allowing for parametric statistical analysis. The median (and 95% confidence limits) for the various semen parameters was 73.0 (10.6-235.3) million sperm per ml; 189.0 (12.6-868) million sperm per ejaculate; 50.4 (5.9-181.9) million motile sperm per ml; 133.0 (6.9-661.7) million motile sperm per ejaculate; 54.0 (7.0-172.9) million morphologically normal sperm per ml and 138.5 (7.5-672) million morphologically normal sperm per ejaculate. Testicular volume was correlated positively with measures of physique such as standardized body weight (r = 0.25, P less than 0.01) and body surface area (r = 0.30, P less than 0.002), and negatively with plasma levels of FSH (r = -0.31), P less than 0.002) but not LH. Sperm output was positively correlated with testicular volume (r = 0.28, P less than 0.005) and negatively correlated with plasma FSH (r = -0.31, P less than 0.002) and plasma LH (r = -0.31, P less than 0.002). Smoking was associated with a highly significant reduction in sperm output and motility. Men with varicocele (25%) were significantly taller, had slightly lower haemoglobin levels and moderate left (but not right) testicular atrophy, but neither seminal nor hormonal parameters were different from men without varicocele. There was no difference in any markers of human testicular function between men according to marital or fertility status, grades of moderate alcohol consumption or the presence of low titres of sperm antibodies.

An autoradiographic search for radioactive particles in the lungs of cigarette smokers

Mucosal samples from the bifuracation of a major bronchus were examined from 23 patients undergoing diagnostic bronchoscopy. Samples were autoradiographed using a technique that avoids any contact between tissue and reagents until the end of autoradiographic exposure. The autoradiographs were scanned for a-particle tracks. No significant level of alpha -activity was detected, even in samples from heavy smokers who had continued to smoke within several hours of the bronchoscopy. The lower limit of detection of a-activity in this experiment was equivalent to about 55.5 becquerrels/kg (1,500 pCi/kg) Polonium-210. These results do not support the hypothesis presented by others that a radioactivity in particulate material of cigarette smoke contributes significantly to the association between cigarette-smoking and bronchial carcinoma.