Determination of Radon Concentration in Some Types of Cigarettes

Transcription

1 Determination of Radon Concentration in Some Types of Cigarettes Tarfa.H.Alsheddi 1, Amal Mohamed 2 and Shaffa.Al.Mansour 3 1 Department of physics, King Faisal University, Saudi Arabia. 2 Department of physics, Zagazig University, Egypt. 3 Department of physics, Dammam University, Saudi Arabia. Received: 20/2/2013 Accepted: 20/3/2013 ABSTRACT Radon concentrations in ten different types of cigarette samples were measured using CR-39 and silicon surface barrier detectors(ssbd). The samples were collected from Saudi and Egyptian markets and were coded k1 to k10. The results obtained from the study of radon ( 222 Rn) and thoron ( 220 Rn) showed that the cigarette brands are moderate in radioactivity while others raise radon concentration in air to ± 0.4 Bq/m 3 (k10 samples). The annual effective dose corresponding to this level is 5531 ± 8 µsvy -1, which is out the security (the maximum permissible dose is 1 msvy -1 ), and so does the least radioactive brand (k4, ± 0.6 Bq/m 3 and 2270 ± 12 µsvy -1 ). Also for k10 samples, the maximum value of annual absorbed dose is 7901 ± 11 µgyy -1,and the minimum value for k4 is 3243 ± 17 µgyy -1. This may be due either to the soil and fertilizers, the additives or to both. This study may provide evidence of the intimate relation between smoke s radon and risk of lung cancer. Key words: Radon/cigarette/Lung cancer/ CR-39dosimeter/Silicon surface barrier Detector. INTRODUCTION Cigarette smoking is considered as the leading cause of lung cancer [1],but radon [2] and secondhand smoke [3] play important roles in lung cancer risk among nonsmokers. Occasionally, radon and secondhand smoke have been considered as carcinogens. Recently, evidence suggests that both may damage lung epithelia by generating reactive oxygen species [4]. Lighted tobacco produces large quantities of reactive oxygen species [4-6],and evidence grew that high lung exposure time radiation need not traverse a cell s nucleus in order to damage the DNA [7,8]. Alpha particles that pass through the cytoplasm may generate oxygen anions and hydrogen peroxide that produce mutations and other DNA lesions [8]. Further, neighbor, non irradiated cells may be damaged via a bystander effect [9,10] where cellular signals from an irradiated cell may induce oxidative stress in adjacent non irradiated cells [8,11]. Radon isotopes of mass number 222 and 220 emanate from the natural radioactive series starting with U-238 and Th-234. The danger of radon is that it is a gas transporting radioactivity from place to another and due also to the short half-lives of both it and its progeny. Alpha activity of radon and its progeny penetrates, with air,into bronchial cells of the lungs, where it may cause a damage leading to cancer. Alpha particles heavily ionize the materials they pass through. CR-39 is a very sensitive plastic that keeps the damage caused by alpha ionization effect for very long times. Etching irradiated CR-39 plastic pieces with sodium hydroxide of proper normality and temperature for appropriate time help prevailing optical microscopically obvious pits for incident alpha particles. To count alpha we took into account the detector efficiency, exposure time and yields radon concentration. Ionization caused by alpha particles in semiconductor silicon is the base of measuring 671

2 radon by radon-scout. The second system measures radioactivity instantly, while the first registers the effect latently until prevailing by chemical etching. The absorbed dose of alpha radiation is calculated by integrating alpha energies absorbed in every mass unit of the exposed system. The effective dose takes account of the radiobiological effectiveness for both alpha and the living tissues exposed. EXPERIMENTAL PROCEDURE The radon level in different smoking samples were measured using two techniques. First technique CR-39 (Intercast, Italy) based radon dosimeter; nuclear track detector with a thickness of 400 µm was used in this work. Measurements were made in 10 different cigarette samples coded k1 to k10. A fixed amount of sample (25 gm, which corresponds to 40 cigarettes) was collected from Saudi and Egyptian markets. Samples were dried, pulverized, homogenized and placed in plastic containers. A piece of CR-39 dosimeterwith area of 1x1 cm 2 was embedded in the sample in each container. At the same time, a second piece of CR-39 detector was held at the top of the container (Fig. 1). The containers were left at room temperature for one month exposure time. During this time α particles from the decay of radon, thoron and their daughters bombard the CR-39 nuclear track detectors in the air volume of the container. After exposure, the detectors were etched chemically with 6.25 N- NaOH solutions at 70 C 0 for 5.5h. The tracks were counted using an optical microscope of X400 magnification. The lower detector recorded alpha particles from radon, thoron and their daughter products present in the cigarette samples. The upper detector, however records only the 222 Rn component. The density of tracks counted was assumed to be proportional to the 222,220 Rn [12]. Air filter cover Can CR-39 detector Sample Fig. (1): The sketch of the radon sampler container. CR-39 plastic detector piece is attached in the top cover to register 222 Rn and another piece in contact with the material to register 220 radon and solid daughters of both. The second technique; Silicon Surface Barrier Detectors (SSBD) counts alpha particle emissions from radon. This system is called Radon-Scout. This system is provided with sensors to measure the temperature and relative humidity during radon measurement. The system outputs are available both in analog and digital display. Determination of the annual effective dose E (msvy 1 ) indoor closed roomby the relation [13,14]; 677

3 E=CxFxHxTxD (1) C is the radon concentration (Bq/m 3 ) F is the equilibrium factor (0.4) H is the occupancy factor (0.8) T is hours in a year (7000 hy -1 ) and D is the dose conversion factor: 9x10-6 msv (Bq/m 3 h) RESULTS AND DISCUSSION Analysis of the charts given by the SSBD was carried out on the average temperature and relative humidity during the year. Table (1) shows the annual effective dose, calculated from equation 1. The annual absorbed dose can be calculated using therelation ; Annual absorbed dose (mgy y -1 ) =[ 0.7 Sv -1 Gy x Annual effective dose (msv y -1 )] (2) The values represented in the table 1 indicated that the cigarette brands are moderate in radioactivity while others raise radon concentration in air to ± 0.4Bq/m 3 ( k 10 sampels). The annual effective dose corresponding to this level is 5531 ± 8 µsvy -1, which is out the security (the maximum permissible dose is 1 msvy -1 ), and so does the least radioactive brand (112.4 ± 0.6Bq/m 3 and 2270 ± 12 µsvy -1 ). Also for k 10 samples, the maximum value of annual absorbed dose is 7901 ± 11 µgyy -1, and the minimum value is3243 ± 17 µgyy -1. Table (1); the annual effective and absorbed dose from differentcigarettesamples. No of samples K1 K2 K3 K4 K5 K6 K7 K8 K9 K10 Radon concentration (Bq/m 3 ) ± ± ± ± ± ± ± ± ± ±0.4 Annual effective dose (µsvy -1 ) 2872 ± ± ± ± ± ± ± ± ± ± 8 Annual absorbed dose (µgyy -1 ) 4103 ± ± ± ± ± ± ± ± ± ± 11 Figure (2) shows the concentration of 222 Rnand 220 Rn in the different cigarette samples. It is obvious from the figure that the highest level of radon-222 is obtained from sample k1 and highest radon-220 level from sample k10 while the lowest corresponding levels are for k2 and k6, respectively. For 220 Rn, alpha particle shares more to the absorbed and effective doses, butfortunately 220 Rnhas shorter half life (55 s) and lower abundance. 671

4 Fig. (2): Histogram of the radon and thoron concentrations in the cigarette samples. Figure (3) shows the relation on which the radon scouts measurement bases. The alpha particle counts relate linearly to radon concentration. The display of the radon-scout is shown in Fig.(4), where the radon concentration level is instantaneously plotted along the measurement period. CONCLUSION The results obtained from this study of radon ( 222 Rn) and thoron ( 220 Rn) in 10 cigarettesamples showed that the highest concentrations were observed in the k10 samples (273.8 ± 0.4 Bq/m 3 ). The annual effective dose corresponding to this level is 5531 ± 8 µsvy -1, which is greater than the maximum permissible dose ( 1 msvy -1 ), and so does the least radioactive brand (k3, ± 0.6 Bq/m 3 and 2270 ± 12 µsvy -1 ).This may be due either to the soil and fertilizers, the additives or to both. 671

5 Fig. (3): The relation between alpha counts and radon concentration using the SSBD.. Fig. (4): The instantaneous radon level displayed by the radon-scout 611

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