Human Exposure to Radioactivity From Tobacco Smoke: Systematic Review

Tobacco has been known to contain radioactive polonium and lead for 50 years but the literature is divided as to the public health significance. I review the data on tobacco radioactivity and its internalization by smokers. Data sources: Reports of lead-210 and polonium-210 content of tobacco leaf, cigarettes, cigarette smoke, and human respiratory tissues, published between 1964 and September 2017. Study selection: Any identified study that reported values for lead-210 and polonium-210 content. Data extraction: Data quality was addressed by comparative review of analytic methods. The data about radiation content of tobacco and smoke are robust. Early reports suggesting microsievert lifetime doses of inhaled radioactivity to smokers were not borne out. The results remain sensitive to pharmacological assumptions around absorption and redistribution of inhaled radionuclides, and radiobiological assumptions about interaction with human tissues. Literature on tobacco radioactivity has not fully contended with pharmacological and radiobiological uncertainty, and is therefore divided as to health significance. This does much to explain regulatory inaction over the last half century. Before radiation safety law can offer a vehicle for tobacco control, more must be learnt about the pharmacology and radiobiology of inhaled radionuclides in tobacco smoke. This work makes it apparent that the study of tobacco smoke radioactivity has been scientifically stagnant for the last 40 years. The field cannot advance until we improve understanding of the pharmacology and radiobiology of inhaled radionuclides in tobacco smoke. Despite this, a subset of contemporary authors is still suggesting individual health risks about 1000 times higher than can be supported by internationally accepted models.