Elements of Natural Radioactive Decay Series in Iranian Drinking Water and Cigarettes

The uranium (²³8U) decay series provides the most important isotopes of elements radium (²²⁶Ra), radon (²²²Rn), and polonium (²¹⁰Po) with half-lives of about 1600 years, 3.8 days, and 140 days, respectively. Although the chemical structure of radium is very similar to calcium, the fact that it produces a radioactive gas (radon) complicates its handling in the laboratory and natural environment. In this study, we used the average concentrations of naturally occurring radionuclide ²²⁶Ra in drinking water at different parts of Iran to estimate the annual effective dose. In the other part of the study, we measured the concentrations of ²¹⁰Po in Iranian cigarettes to estimate the internal intake of this radionuclide and its concentration in the lung tissues of smokers. The results indicate that the average concentration of ²²⁶Ra in Iranian drinking water was below the 100 mBq L^-1 recommended by the World Health Organization while the average concentration of ²¹⁰Po and ²¹⁰Pb in Iranian cigarettes was relatively high in comparison with other cigarettes found on the market.