Survival Analysis of Victims of Sulfur Oxide Air Pollution Suffering from COPD or Asthma in Yokkaichi, Japan, in Relation to Predisposing Exposure

To investigate the relationships between clinical findings and symptoms and the survival of patients with Yokkaichi Asthma, in relation to predisposing sulfur dioxide (SO2) exposure, we examined records of 1836 patients registered in the city of Yokkaichi during 1973-1988 by “Pollution-Related Health Damage Compensation Law.” Complete records were obtained from 735 patients (352 males and 383 females) until December 31, 2007, and were used for the analysis. Ambient SO2 concentrations in the Yokkaichi area were obtained from the Environmental Numeric Database of the National Institute for Environmental Science, Japan. It was found that severity of clinical symptoms and decreased pulmonary function were significantly correlated with predisposing SO2 exposure. A Cox proportional hazards analysis revealed that among all patients (COPD and asthma), age, forced expiratory volume 1.0 (sec) % and smoking affected mortality for both males and females. Significant associations between mortality, vital capacity (percent predicted) and cough and sputum were observed in males. Thus, the survival of patients with Yokkaichi Asthma was affected by severity of clinical symptoms and decreased pulmonary function, which were related to predisposing SO2 exposure. It appeared that the effects of clinical changes were greater in males than in females.