COMPARISON BETWEEN THE LOCALIZATION OF LUNG-TUMORS IN URANIUM MINERS AND IN NONMINERS FROM 1947 TO 1991

BACKGROUND. Lung cancer was noted to be increased in cigarette smoking miners and nonminers. Carcinogen particulates deposit differentially in the central, middle, and peripheral zones of the bronchial tree dep ending on the size of the particle. The object of this study was to ev aluate the incidence of tumors; their cell types; and the relationship of particulate size to their position in the bronchial tree. METHODS. Tumor position in the bronchial tree was studied for a cohort of 467 uranium miners and 311 nonminers with lung cancer. RESULTS. An examina tion of all histologic subtypes showed that the proportion of lung can cers in the central zone was significantly greater in miners than in n onminers presumably due to the deposition of radon decay products atta ched to the silica dust particles. The higher percentage of central tu mors in the miners was primarily due to the distribution of a greater proportion of squamous cell and small-cell tumors. The ratio of 0.75 f or the central to middle and peripheral location for adenocarcinomas w as much lower than for squamous cell and small-cell carcinomas with ra tios of 1.4 and 7.3, respectively. In the mining cohort, there were te n times as many small-cell tumors in the central area as in the middle and peripheral regions, whereas, for the nonminers there were only fi ve times as many centrally located small-cell tumors as middle and per ipheral (chi square is 7.0 degrees, P < 0.01). These data suggest that radon may be deposited preferentially to the central region of the lu ngs in uranium miners. CONCLUSIONS. Based on our observations of the d ifferential positions of lung tumors in the bronchial tree for miners and nonminers and previous studies by others regarding size-dependent deposition of particulates in the bronchial tree, it is concluded that inhaled dust, radon, and cigarette smoke combine to form large partic ulates that deposit in the central bronchial tree. Filtered cigarette smoke or other small carcinogens form smaller particulates that deposi t more peripherally. (C) 1995 American Cancer Society.