Follow-up study on pulmonary function of dust workers: an epidemiological evaluation of discontinued workers of dust...

An epidemiologic study on 176 dust workers from various facilities was initiated in 1978. Their mean age was 48.3 years and mean duration of employment was 21.6 years. No workers complained of chronic cough and phlegm. Their chest X-rays were found to belong to Category I of the diagnostic criteria for pneumoconiosis in Japan. Pulmonary function test was performed on these workers, however, 54 workers discontinued taking part in the study by the end of 1979, and 49 workers had discontinued by 1981. A total of 73 workers had a five-year follow-up survey of pulmonary function. Forced expiratory volume in one second divided by forced vital capacity (FEV1.0/FVC) and forced expiratory flow rate at 25% of FVC divided by height (V25/H) were mainly compared by smoking habit, work years, type of job, size of company, and the time when they discontinued their jobs. Predicted percentage values of lung function were used for the adjustment of the influence of workers' ages. Decrement of FEV1.0/FVC and V25/H in the five-year follow-up group were larger than the screening level. The mean values of those functional parameters in the early discontinued group were lower than late discontinued and active working groups. The active working group was considered to be a physically healthy workers' population.