[Follow-up studies on chronic obstructive pulmonary disease among Ookunojima poison gas workers]

A high prevalence of chronic bronchitis has been reported among former employees of a poison gas factory in Ookunojima. The author has studied changes in clinical features by analyzing chest X-ray, sputa and respiratory function in 72 cases whose clinical courses could be observed for the 10 year period from 1981 to 1991. FEV1.0 in the patients with emphysematous change on chest X-ray was significantly decreased as compared to that of patients with inflammatory change and those with normal findings. FEV1.0 in the obstructive and infectious-obstructive type groups, in terms of clinical classification of chronic bronchitis, was significantly decreased as compared to that of simple and inflammatory types. These results show that the obstructive ventilation disorder in these two groups is progressive. Next, the author analyzed CT findings of the whole lung in 93 cases, including the former 72 cases. %(I-E) represents the alteration ratio of whole lung field CT numbers during full inspiration and full expiration. %(I-E) in the emphysematous group was significantly decreased as compared to the other two groups. %(I-E) showed a good correlation with FEV1.0 (r = 0.645), FEV1.0% (r = 0.500) and V50/V25(r = 0.523). This parameter was considered to be useful for evaluation of the obstructive ventilation disorder in these cases. The chronic bronchitis in these poison gas workers has been reported to be predominantly inflammatory and to have a variable clinical course. However, our results show that progression of the obstructive ventilation disorder caused by emphysematous change produces long term deterioration of pulmonary function in poison gas workers.