PULMONARY AIR SPACE SIZE IN COAL-MINERS

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Abstract
Persistence of a monodisperse aerosol (mean diameter, 0.55 .mu.m) in the human respiratory tract decreases exponentially with time of breath holding. The disappearance of aerosol from inspired gas with and without breath holding was expressed as half-life (t 1/2) of aerosol persistence. The t 1/2 of aerosol persistence can be used to estimate the average or effective diameter of the parenchymal air space. Aerosol t 1/2, lung volumes, maximal expiratory flow at 50% vital capacity, airway resistance and single-breath CO diffusing capacity were measured in 35 underground coal miners with radiographic category O (no) pneumoconiosis, 34 with radiographic type q (micronodular) pneumoconiosis and 58 with type p (pinhead) pneumoconiosis. There were no significant differences between the miners with type p and those with type q simple pneumoconiosis with regard to mean height, age, total lung capacity, forced vital capacity, ratio of forced expiratory volume in 1 s to forced vital capacity, maximal expiratory flow at 50% vital capacity or CO diffusing capacity. Miners with type p opacities had a significantly longer mean aerosol persistence (t 1/2) than did miners with either type q or those with no (category O) pneumoconiosis. The mean t 1/2 values for the latter 2 groups did not differ significantly from previously reported values for 36 male nonminers. The mean percentage of aerosol recovered at zero breath holding time was significantly less for miners with type p pneumoconiosis than for miners with type q or no (category O) pneumoconiosis. The smaller percentage recovered at zero breath holding time was also associated with cigarette smoking and symptoms of bronchitis. Underground coal miners with type p pneumoconiosis have narrower small conducting airways and abnormally large peripheral air spaces. These differences are probably related in some way to the reaction in coal miners to dust deposition and cigarette smoking.

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