Comprehensive survey of radionuclides in contemporary smokeless tobacco products

There is considerable interest in the chemical composition of smokeless tobacco products (STPs), owing to health concerns associated with their use. Previous studies have documented levels of ²¹⁰Po, ²¹⁰Pb and uranium in STP samples. Here, the levels of 13 α-particle and 15 β-radiation emitting radionuclides have been measured in a broad and representative range of contemporary STPs commercially available in the United States and Sweden. For each radionuclide, the level of radioactivity and calculated mass per gram of STP are reported. The results indicate that, among 34 Swedish snus and 44 US STPs, a more complex radionuclide content exists than previously reported for these products. Of the 28 radionuclides examined, 13 were detected and quantified in one or more STPs. The most frequently identified radionuclides in these STPs were ⁴⁰K, ¹⁴C, ²¹⁰Po and ²²⁶Ra. Over half the STPs also contained ²²⁸Th, and an additional 8 radionuclides were identified in a small number of STPs. The presence of ¹⁴C, ³H and ²³⁰Th are reported in tobacco for the first time. The activity of β-emitters was much greater than those of α-emitters, and the β-emitter ⁴⁰K was present in the STPs with both the greatest radioactivity and mass concentrations. Since the three radionuclides included in the FDA's HPHC list were either not detected (²³⁵U), identified in only three of 78 samples (²³⁸U), and/or had activity levels over fifty times lower than that of ⁴⁰K (²¹⁰Po, ²³⁸U), there may be a rationale for reconsidering the radionuclides currently included in the FDA HPHC list, particularly with respect to ⁴⁰K. Using a model of the physical and biological compartments which must be considered to estimate the exposure of STP users to radionuclides, we conclude that exposure from α-emitters may be minimal to STP users, but ⁴⁰K in particular may expose the oral cavities of STP users to β-radiation. Although a more comprehensive picture of the radioisotope content of STPs has emerged from this study, epidemiological evidence suggests that the levels of radionuclides measured in this study appear unlikely to present significant risks to STP users.