Abstract

Since 1952 two to three deaths from primary cancer of the lung have occurred regularly each year among the male inhabitants of the small fluorspar mining community of St. Lawrence, Newfoundland. These constituted 23 of the 51 deaths that occurred during the 10-year period 1952-61 among employees with one or more years of underground mining experience. A shift to a younger average age at death from lung cancer and an association between age at entry into risk and age at death were observed. Comparisons between the mortality experience of the inhabitants of St. Lawrence, of a control community of comparable size in the same geographical region, and of the population of the rest of Newfoundland confirmed the probability of an occupational factor, the observed death rate from lung cancer being about 29 times the expected.

The outstanding environmental finding in the fluorspar mines was the discovery of concentrations of radon and daughter products in the air well in excess of suggested maximum permissible concentrations. On the basis of these concentrations and other considerations, it is suggested that undergound workers were probably exposed to an average potential alpha-energy to complete decay of between 2·5 and 10 times the previously suggested working level of 1·3 × 10⁵ Mev per litre of air (Holaday, Rushing, Coleman, Woolrich, Kusnetz, and Bale, 1957). That these levels were obtained in mines in which no radioactive ore bodies have been found is of exceptional interest.

The findings at St. Lawrence are compared with those reported in the literature for uranium mines.