Ventilatory function in Nigerian coal miners

Abstract

Ventilatory capacity has been measured in 675 Nigerian colliery employees classified in three groups according to occupation: coalface workers, other underground workers with low exposure to dust, and surface workers in administrative and clerical jobs. Men with current respiratory symptoms were excluded, as were ex-miners. The faceworkers were a slightly older group who smoked less, and they were presumed to be more active. Faceworkers had the highest forced vital capacities (adjusted for age and stature) but the lowest values for indices reflecting maximal expiratory airflows (FEV1/FVC, PFR, FEF and FMF). Apparently coalface work is associated with an 8% impairment of maximum expiratory airflow, probably due to dust exposure, but also with a modest enhancement in FVC, possibly due to training of the respiratory muscles. Regression coefficients on age for the airflow indices are significantly more negative in faceworkers than in the other groups. Smoking and duration of service did not significantly affect the pattern of results. FEV1 does not vary among the occupational groups in the colliery, and the mean value is close to that predicted on the basis of reference equations previously obtained for non-miners in Nigeria.