br Am radionuclides The following radionuclides
241 Am radionuclides. The following radionuclides with their respective peaks were used to determine the experimental full-energy peak efficiency (FEPE) curve with energies in the range 45—2615 keV.
Annual effective dose and excess life time cancer risk assessment from tobacco plants 3
Table 2 Annual effective dose and ELCR of smokers due to smoking different brands of tobacco.
concentration A(E) in Bq kg−1 of the radionuclides found in the samples was calculated using the following relation: A(E ) = Cnet (1)
where Cnet is the counting rate for a specific gamma line (counts per second) corrected for background, ε(E) is the absolute photopeak efficiency, I is the intensity of the con-sidered gamma-ray line, t is the counting time in s and m is the sample mass in kg.
Results and discussion
137 Cs activity concentrations in the tobacco Cyclosporin H ranged from 0.15 ± 0.01 to 0.67 ± 0.9 (average 0.44) Bq kg−1. This concentration could be due to root uptake. Results showed that the highest activity concentration was in TAB1.
Assessment of radiological hazards
The knowledge of the radioactivity content of the vari-ous radionuclides in the investigated samples is important to assess the radiological hazard effects to human health through radiation hazard indexes.
The radium-equivalent activity (Raeq) index is used to compare the activity concentration levels of 226Ra, 232Th and 40K in the materials and it takes into account the gamma
radiation hazards associated with them. It is calculated through the relation given by (Beretka and Mathew, 1985):
where ARa, ATh and AK are the measured activities for the radionuclides 226Ra, 232Th and 40K, respectively. The per-missible maximum value of the radium equivalent activity should be less than 370 Bq kg−1, in order to limit the annual effective dose to 1 mSv for the general public as reported by UNSCEAR (1982). The results for the calculation of Raeq show that Raeq values in the investigated tobacco samples ranged from 54.2 to 109.53 (average 88.34) Bq kg−1 which is lower than the recommended limit of 370 Bq kg−1.
For cigarettes, it was assumed that an adult person consumes about 30 cigarettes (one and a half packs) of 0.82 g of tobacco per cigarette. Then the annual consump-tion of tobacco will be 8.985 kg y−1. According to Khater (2004), about 75% of the radionuclide activity concentration (Bq kg−1) contained in cigarette smoke was partially inhaled and deposited in lung tissues and about 25% is retained in the cigarette filter and ash. The annual effective dose, HE (Sv y−1), due to inhalation for adult smokers, was calculated according to equation:
Excess lifetime cancer risk (ELCR) is the risk that some-one has of getting cancer if that person were exposed to cancer-causing materials for a long time. It is calculated assuming that there is a linear relationship between dose
and the stochastic effects. The ELCR factor can be estimated using the following equation (Taskin et al., 2009):
where AED is the annual effective dose equivalent, DL is the average life exposition expectancy (assumed to be 70 years) and RF is the fatal cancer risk factor per Sievert, which is stochastically determined by ICRP (1990) to be 0.05 for the public.
The radioactivity concentrations of 226Ra, 232Th and 40K as well as the artificial radionuclide 137Cs in tobacco leaves samples as investigated using gamma ray spectrometry showed that there are low level activities in the studied locations. The activity concentrations in the tobacco leaves would be either through root uptake or through the fertil-izers used for cultivation of tobacco plants in the fields. In estimating the radiation dose induced from smoking, it was concluded that the annual effective dose to lungs due to inhalation for adults (smokers) averaged to 1.2 mSv y−1 for
226 Ra, 0.16 mSv y−1 for 232Th and 0.03 mSv y−1 for 40K giving total of 1.39 mSv y−1. The annual effective dose due to 137Cs averaged to about 25 nSv, which is very much lower than that of the naturally occurring radionuclides. The effective dose of 1.39 mSv y−1 can be compared with the average world-wide exposure to natural radiation sources due to inhalation of 1.26 mSv y−1. Excess lifetime cancer risk was also aver-aged to the value 4.88 × 10−3 that is higher than world’s average of 1.45 × 10−3 for tobacco and coal samples. This study may be taken as a basic to continuous measurement of naturally occurring radionuclides for imported tobacco leaves, processed cigarettes and other tobacco products in order to protect the population from risks caused by tobacco smoking.