Radioactivity of cigarettes and the importance of 210Po and thorium isotopes for radiation dose assessment due to smoking
Tobacco and tobacco smoke are very complex mixtures. In addition to various chemical and organic compounds they also contain natural radioactive elements (radionuclides). In this work, the natural radionuclide activity concentrations (234U, 238U, 228Th, 230Th, 232Th, 226Ra, 210Pb and 210Po) of nine different cigarette samples available on the Slovenian market are reported. In addition to 210Po, the transfer of thorium isotopes from a cigarette to a smoker's body and lungs have been determined for the first time. Cigarette smoke and exhaled air from smokers' lungs were collected from volunteer smokers (C-4 brand) to determinate what quantity of 210Po and thorium isotopes is transferred from the tobacco to the smoker's lungs. Cigarette ash and smoked filters were also collected and analysed. Among the determined isotopes, 210Pb and 210Po showed the highest activity concentrations. During the smoking of one cigarette approximately 22% of 210Po (and presumably its predecessor 210Pb), 0.6% of 228Th, 24% of 230Th, and 31% of 232Th are transferred from the cigarette and retained in the smoker's body. The estimated annual effective dose for smokers is 61 μSv/year from 210Po; 9 μSv/year from 210Pb; 6 μSv/year from 228Th; 47 μSv/year from 230Th, and 37 μSv/year from 232Th. These results show the importance of thorium isotopes in contributing to the annual effective dose for smoking.