Effect of Volcanic Activities of Mt. Sakurajima on the Morbidity Figures for Respiratory and Other Diseases

Abstract

Utilizing the medical facility consultation records of national health insurance system, morbidity figures for selected respiratory dieases, conjunctivitis and dermatitis covering one year period from April 1984 to March 1985 were compared between the two local communities, Sakurajima town and Ohura town. The former town situates in a high ash area at the north-west foot of Mt. Sakurajima, whereas the latter town located about 50 km south-west of this volcano was selected as an ash free control area. Results obtained are as follows:
1) Age-adjusted rates of incidences and prevalences for bronchitis, asthmatoid disease and pneumonia were significantly higher in Sakurajima town than in Ohura town, whereas those for common cold were significantly lower in the former town than in the latter town and those for emphysema were not significantly different between the two towns.
2) In Sakurajima town, the number of monthly clinic visits for the patients with asthmatoid diseases correlated significantly with the coincident levels (measured as monthly average of hourly levels or monthly maximum of daily average) of sulfur dioxide rather than those of total suspended particles. On the other hand, there was no significant correlation between Sakurajima town and Ohura town regarding the number of monthly clinic visits for patients with asthmatoid diseases. These facts suggested that, in Sakurajima town, at least part of the monthly variation for the number of patients visited to clinics with asthmatoid diseases was not seasonal but a reflection of elevated levels of sulfur dioxide in the environment.
3) For the other respiratory disesaes (bronchitis, pneumonia, emphysema and common cold) in Sakurajima town, however, no significant correlations were found between the number of monthly visits for these diseases and the coincident levels of sulfur dioxide or total suspended particles.On the other hand, there were significant positive correlations between Sakurajima town and Ohura town for the number of monthly visits for these respiratory diseases. These facts suggested that the monthly variations in the number of visits for these respiratory diseases were mainly seasonal rather than the effect of volcanic air pollution.
4) For conjunctivitis, the number of new cases which were considered to be related to volcanic ash particles was significantly greater in Sakurajima town than in Ohura town, while the number of recurrent cases was significantly greater in Ohura town than in Sakurajima town. On the other hand, age-adjusted rates of incidences and prevalences for dermatitis were not significantly different between the two towns.