Polonium-210 budget in cigarettes

https://doi.org/10.1016/S0265-931X(03)00118-8Get rights and content

Abstract

Due to the relatively high activity concentrations of 210Po and 210Pb 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. 210Po 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 208Po for chemical recovery calculation. The samples were dissolved using mineral acids (HNO3, HCl and HF). Polonium was spontaneously plated-out on stainless steel disks from diluted HCl solution. The 210Po 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 210Po 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 210Po in cigarette tobacco was 16.6 (9.7–22.5) mBq/cigarette. The average percentages of 210Po 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 210Po and 210Pb each. The annual effective doses were calculated on the basis of 210Po and 210Pb 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 μSv from 210Po and 210Pb, respectively.

Introduction

Polonium-210 (which has a physical half-life time of 138 days) is a member of the natural uranium-238 series and one of the relatively long-lived radionuclides of radon decay products. It is an alpha-emitting radionuclide and is present in trace amounts in most plants and foodstuffs as well as in human tissues (Batarekh and Teherani, 1987). The polonium isotopes are among the most radiotoxic nuclides to human beings. The concentrations of 210Po in cigarette tobacco are in the range of 2.8–37 Bq/kg and vary with the cigarette brand, probably due to the different varieties of tobacco used and to different manufacturing procedures (Skwarzec et al., 2001b). The results obtained by Radford and Hunt (1964) indicate that 210Po in cigarettes is volatilized at the temperatures characteristic for burning cigarettes and inhaled into the lung along with the cigarette smoke (mainstream smoke). It might effectively be a factor in the increased incidence of lung cancer among cigarettes smokers (Radford and Hunt, 1964). Since then, other investigators have studied both the sources and behavior of 210Po and 210Pb in relation to smoking, and the biological effects of these on lung tissues and other organs (Batarekh and Teherani, 1987, Black and Brethauer, 1968, Boltzman and Ilcewicz, 1966, Cohen et al., 1979a, Cohen et al., 1979b, Fletcher, 1994, Godoy et al., 1992, Karali et al., 1996, Martell, 1974, Mussealo-Rauhammaa and Jaakkola, 1985, Nada et al., 1999, Rajewskey and Stahlhofen, 1966, Shabana et al., 2000, Sinh and Nilekani, 1976, Tso et al., 1964, Tso et al., 1966, Watson, 1985). Tso et al. (1966) reported that the principal source of 210Pb and thus also of 210Po in tobacco is the soil and the contribution of polonium from atmosphere onto the tobacco plant to the total activity in the plant is minor compared to the polonium absorbed from the soil via the roots (Tso et al., 1966). In contrast Skwarzec et al. (2001b) indicated that the atmospheric deposition is the main source of 210Po in the tobacco leaves. It is known to be absorbed to sub-micron-sized particles present in the smoke. Lead-210 is not sublimated at this temperature, but is rather a component of the resulting smoke and ash (Watson, 1985). Lead is inhaled with the particulate fraction of mainstream smoke and acts as long-term source of 210Po exposure. Both radionuclides contribute to cancer risk due to their deposition in the tissue of the lungs (Fletcher, 1994, Karali et al., 1996, Martell, 1974, Watson, 1985).

About 6.5–22% of the 210Po contained in cigarettes was found in the mainstream smoke (Mussealo-Rauhammaa and Jaakkola, 1985, Radford and Hunt, 1964). Other authors have reported different percentage values, ranging from 3.7 to 58%. On average, approximately 50% of the 210Po in cigarette tobacco is transferred to the smoke, 35% remains in the butt and approximately 15% is found in the ash (Parfenov, 1974). Numerous variables govern the degree of exposure via the pathway of tobacco smoke: the geographic region where the tobacco is grown, the fineness of the tobacco cut, the presence or absence of a filter, the size and composition of the filter and smoking habits (Watson, 1985).

It has been reported that the content of other carcinogens in tobacco today has been greatly reduced by means of changes in tobacco processing methods and the use of modern cigarette filters, but these have little effect in terms of reducing radioactivity levels. Although, in the last few years, many studies have been carried out to investigate the reduction in trace element and other toxic substances in cigarettes achieved through the use of modern tobacco processing techniques and filter materials, only few studies have been carried out to investigate the reductions in radioactivity levels.

This work was aimed in determining 210Po specific activity in most frequently smoked Egyptian cigarettes in order to estimate the annual effective dose to cigarettes smokers due to 210Po and 210Pb inhalation via smoking. This work is a part of the national program to estimate the radioactivity contents of consumer products. Due to a large-scale consumption of tobacco in Egypt at the present time, we found this study to be a necessity. Also, it is providing the first new data available since that of Black and Brethauer (1968).

Section snippets

Experimental work

Ten samples of Egyptian produced fine and popular brands of most frequently smoked cigarettes in Egypt were randomly selected from those available on the market. Although each brand has several types of cigarettes, only the most popular one was chosen for analysis. Five cigarettes were taken from each pack to provide combined samples from different parts of the cigarettes, i.e. fresh tobacco, wrapping papers and fresh filters. A further five cigarettes were taken from the same pack and smoked

Results and discussion

The average (range of) activity concentrations of 210Po in cigarettes tobacco, wrapping paper, fresh filters, ash and post-smoking filters from fine and popular brands of the Egyptian cigarettes are presented in mBq/g and mBq/cigarette in Table 1. The activity concentrations of 210Po in mBq/cigarette present in the cigarette tobacco, wrapping paper, ash and post-smoking filters, and the smoke, and the percentages of 210Po recovered in cigarettes ash, post-smoking filters and smoke are presented

Conclusions

Cigarette smoking increases the internal intake of 210Po and 210Pb, which are contained in cigarette tobacco in relatively high concentrations. Polonium-210 and 210Pb that are inhaled and deposited in the lung tissues will contribute to an increase in the internal radiation dose and in the number of lung cancer incidences observed among smokers. The results of this work indicate that the average activity concentration of 210Po in Egyptian cigarettes tobacco is 16.3 mBq/cigarette, with a range

Acknowledgements

I wish to express my deep gratitude to Dr. Max Pimpl for reviewing the manuscript. The author wish to acknowledge the support received from the International Bureau of Forschungszentrum Julich in Germany.

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