Radioactivity of ²¹⁰Pb in Japanese cigarettes and radiation dose from smoking inhalation

It is well known that cigarette tobaccos contain naturally occurring radioactive nuclides such as ²¹⁰Pb and ²¹⁰Po. In many countries, the radioactivity of tobaccos has been measured to estimate the effective dose from smoking inhalation. The present study covered 24 cigarette brands including the top 20 of sales in Japan between April 2008 and March 2009. The activity concentrations of ²¹⁰Pb were measured by gamma-ray spectrometry, and then those of its progeny ( ²¹⁰Po) were evaluated assuming the radioactive equilibrium between the two nuclides. Their concentrations were in the range of 2-14 mBq cigarette. ^-1 with an arithmetic mean of 8±3 mBq cigarette. ^-1. The annual committed effective doses were also calculated, based on the scenario that a smoker consumes 20 cigarettes a day. The average doses from ²¹⁰Pb and ²¹⁰Po inhalations were 22±9 and 68±27 uμSv y. ^-1, respectively.