polonium and Carcinoma--Bronchogenic

Topics: Animals; Background Radiation; Body Burden; Carcinoma, Bronchogenic; Environmental Health; Fishes; Humans; Lichens; Lung Neoplasms; Mining; Neoplasms, Radiation-Induced; Plankton; Plants; Polonium; Radiation Dosage; Radioactive Fallout; Reindeer; Shellfish; Smoking; Uranium; Vehicle Emissions

The effectiveness of radon-daughter inhalation and irradiation with fission neutrons and gamma rays in the induction of lung carcinomas in Sprague-Dawley rats at low doses is compared. Earlier reports which compared radon-daughter inhalations and neutron irradiations over a wider range of doses were based on dosimetry for the radon-daughter inhalations which has recently been found to be faulty. In the present analysis, low-dose experiments were designed to derive revised equivalence ratios between radon-daughter exposures, and fission neutron or gamma irradiations. The equivalence is approximately 15 working level months (WLM) of radon daughters to 10 mGy of neutrons (the earlier value was 30 WLM to 10 mGy). The relative biological effectiveness (RBE) of neutrons is 50 or more at a gamma-ray dose of 1 Gy. In these experiments with low doses and exposures, the lifetime incidences can be estimated from the raw incidences, while the derivation of the time dependence of the prevalence is essential for the estimation of RBE values and equivalence ratios.

Topics: Administration, Inhalation; Animals; Bismuth; Carcinoma, Bronchogenic; Cobalt Radioisotopes; Gamma Rays; Lead; Lung Neoplasms; Male; Neoplasms, Radiation-Induced; Neutrons; Polonium; Radon; Radon Daughters; Rats; Rats, Inbred Strains; Relative Biological Effectiveness; Sarcoma, Experimental

The alpha-activity on the bronchial airways has been calculated for 222Rn daughter exposures producing observable excess bronchogenic lung cancer in underground miners. The activity distribution of aerosol particles with attached 222Rn daughters on the bronchial tree is truly diffuse because of the short half-life of the daughters and the large number of particles in the ambient aerosol. From the bronchial airway activity and the minor epidemiology, it can be shown that it requires, on average, 4 X 10(9) stem cells in bronchial epithelium to be hit in order to produce an observed lung cancer. For very high 222Rn daughter exposures of miners, multiply hit cells are highly probable; yet the lung cancer response is lower per unit exposure at high exposures than for mining exposures--near those sustained in the environment probably due to stem cell death. A knowledge of the number of multiply hit cells in miners permits some infererences to be made about the effectiveness of particulate versus diffusely distributed alpha emitters in the lung, namely, that particulates should not be significantly more effective in lung cancer induction than a diffuse distribution.

Topics: Air Pollution, Radioactive; Alpha Particles; Bismuth; Bronchi; Carcinoma, Bronchogenic; Humans; Lead; Lung Neoplasms; Mining; Neoplasms, Radiation-Induced; Polonium; Radon Daughters

Topics: Bismuth; Carcinoma, Bronchogenic; Humans; Lead; Lung Neoplasms; Neoplasms, Radiation-Induced; Polonium; Radon Daughters; Smoking

Topics: Austria; Bronchial Neoplasms; Carcinoma, Bronchogenic; Humans; Mining; Nicotiana; Polonium; Radiation Injuries; Radon; Toxicology; Uranium