A survey of respiratory symptoms, lung function tests, and chest radiography was carried out among the fluorspar miners of St. Lawrence, Newfoundland, in whom the incidence of carcinoma of the lung (De Villiers and Windish, 1964) had previously been shown to be 25 times greater than for the rest of the province.
The incidence of pneumoconiosis among the exposed population was low (1·93%) and the incidence of `chronic bronchitis' comparable to that reported for miners elsewhere, enabling one to dismiss these as a relevant factor in the high incidence of carcinoma.
The relevance of smoking is less easy to assess in these miners, among whom there are few non-smokers and many heavy smokers. Extrapolation from the data of Doll and Hill (1956) suggests, however, that the prevalence of heavy smoking among the miners cannot be the sole factor responsible for the higher incidence of carcinoma compared with the rest of Newfoundland, but it might well be a contributory one. It appears therefore that the main factor causing the high incidence of carcinoma among these miners was the high level of radioactivity in the air and water in the mines (De Villiers and Windish, 1964).
The reduction in lung function tests appeared to be more closely related to the presence of bronchitis than to dust exposure, but the incidence of chronic bronchitis was apparently higher in men exposed for any length of time to dust risk than in men with insignificant exposure.
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