Vilma R. Hunt

Polonium-210: A Volatile Radioelement in Cigarettes.

Polonium-210, which emits alpha particles, is a natural contaminant of tobacco. For an individual smoking two packages of cigarettes a day, the radiation dose to bronchial epithelium from Po210 inhaled in cigarette smoke probably is at least seven times that from background sources, and in localized areas may be up to 1000 rem or more in 25 years. Radiation from this source may, therefore, be significant in the genesis of bronchial cancer in smokers.

Distribution of Polonium 210 in Pulmonary Tissues of Cigarette Smokers.

Concentrations of the alpha-particle-emitting radioactive element polonium was measured in various pulmonary tissues of smokers and nonsmokers in order to determine 1) whether this radiation exposure is associated with the development of bronchial cancer in smokers; and 2) how smoke is absorbed and excreted in human lungs. Lung specimens from 25 current cigarette smokers, 2 current pipe smokers, 1 former cigarette smoker, and 8 nonsmokers ere analyzed. The average concentration of polonium in the peripheral parenchyma of current smokers was .0074 picocurie/gm and in nonsmokers was .0016. For smokers, the average concentration was doubled in more centrally located parenchyma and was greater in the upper than in the lower lobes. Polonium concentrations correlated with daily cigarette consumption but not with total cigarettes smoked. The concentrations in peribronchial lymph nodes of smokers were also higher than in nonsmokers. These values show no correlation with total or daily cigarette consumption. Polonium concentration was similiar in bronchial wall parenchyma as in lung parenchyma but was greater in bronchial epithelium than in parenchymal or lymph nodes. The patterns of distribution of polonium throughout the lung suggest that most inhaled smoke particles are rapidly cleared from the lung, and polonium is primarily cleared by mucus sheet. Since the highest local concentrations of polonium were found in bronchial epithelium from segmental bifurcations, leading to a high cumulative local radiation dose, polonium may be implicated in the initiation of bronchial cancer in humans.

COMPARISON OF CONCENTRATIONS OF ALPHA-EMITTING ELEMENTS IN TEETH AND BONES.

SummaryTo evaluate the suitability of teeth as indicators of the skeletal burden of alpha-emitting elements, variability of content of 226Ra, 210Pb, and 228Th has been determined: (a) for different teeth from the same individual, and (b) between tooth levels and the amount in bone samples from the iliac crest in the same individual.There was a significant correlation between the levels of 210Pb and 226Ra in teeth compared with iliac crest, supporting the conclusion that teeth are adequate samples to estimate human skeletal burdens of these alpha-emitting elements.Preliminary results are given indicating that local variations within individual bones or teeth may be considerable; thus any small sample of calcified tissue may be an inadequate indicator of total-body burden. Even so, teeth are as satisfactory as small bone fragments for comparing levels in groups of human subjects.

Autoradiographic Studies of the Distribution of Polonium-210 in Mice after a Single Intravenous Injection

SummaryThis short-term autoradiographic study has been undertaken to give survey distribution patterns of all organs and tissues simultaneously before severe tissue changes due to radiation damage were apparent.The results confirmed earlier autoradiographic studies. In addition, we have shown the importance of the accumulation of polonium in the placenta, the uptake in the organic matrix of bone. High concentrations were also found in the lacrymal and mammary glands, the meninges, and in the intestinal wall.