European Journal of Epidemiology 10: 291-297, 1994. © 1994 Kluwer Academic Publishers. Printed in the Netherlands. The evolution of pulmonary tuberculosis in coal miners in Asturias, Northern Spain An attempt to reduce the rate over a 15-year period, 1971-1985 J.A. Mosquera l, L. Rodrigo 2 & F. Gonzfilvez 3 1Department of Pulmonary Medicine, 2 Department of Internal Medicine, 3 Department of Thoracic Surgery, Institutio Nacional de Silicosis, Ovieto, Spain Accepted in revised form 22 April 1994 Abstract. A prospective study of 53,753 coal miners was undertaken at the Instituto Nacional de Silicosis (INS) in Asturias, Spain, during the period 1971 to 1985. This included a complete medical history, physical examination, pulmonary function tests, and intensive search for pulmonary tuberculosis. A total of 1,136 new cases of active pulmonary tuberculosis were found, all of which were confirmed by bacteri- ology. The average incidence was 150 + 31 cases per 100,000 miners year-1. Annual analysis revealed that this figure remained fairly stable during the period of study. Only a reduction of the prevalence in the subgroup of miners with massive pulmonary fibrosis was seen in later years. The risk of tuberculosis among miners was three times greater than that for the general population of the same area. Our inability to reduce the incidence of pulmonary tuberculosis in a large group of coal miners, in spite of the fact that the treatments given were effective and that in the last eight years chemoprophylaxis was given to close contacts, should be emphasized. Key words: Coal workers pneumoconiosis, Progressive massive fibrosis (PMF), Silicotuberculosis, Tuberculosis Introduction Different studies employing mortality indexes and rates of infection have been carried out on the epi- demiology of pulmonary tuberculosis. These have permitted the formulation of the hypothesis of a probable rapid disappearance of the disease, at least, in more industrialized Western countries [1, 2]. When we carefully analyse the data based on the rates of disease in recent years, conclusions can be drawn that if the prevalence of tuberculosis (TB) continues at its present rate, this disease and the increment of such seen in patients with AIDS and other debilitating diseases will not disappear in the near future [3]. A well-known double interaction exists between pulmonary tuberculosis and pneumoconiosis in coal workers. On the one hand, pulmonary silicosis implies an increased risk of suffering pulmonary tuberculosis, probably as a consequence of coal par- ticles inhaled into the alveoli of the lung, with later destruction by phagocytes. On the other hand, the appearance of pulmonary tuberculosis in the course of coal worker pneumoconiosis induces the progres- sion toward a picture of progressive massive fibrosis (PNF) [4]. This consequently implies the transfor- mation of uncomplicated forms of TB with little or no functional effect and good life expectancy, into complicated pneumoconiosis with a decrease of res- piratory pulmonary capacity and the appearance of multiple complications that shorten the life expectancy of these patients [5-7]. In our experience pulmonary tuberculosis is the commonest cause of complicated pneumoconiosis in coal workers. Thus any attempt to reduce its incidence is based on early detection and efficient treatment of the disease with currently available drugs. The aim of the present work was to analyse the evolutive data of the incidence of pulmonary tuberculosis in a relatively stable coal mining population over a period of time (in our case fifteen years), and also to evaluate the effectiveness of the different types of treatment used throughout the period of the study. Material and methods Asturias is located in northeast Spain and has a stable population of around one million two hundred thousand people. One of its main industrial activi- ties is coal mining. During the study period, an average of 29,949 + 1,413 persons were employed in this activity. The number of people who formerly worked in the mines and who were, at the time, retired was 21,522 + 7,368, all of whom constitute the target population under analysis (Figure 1).