Influence of sulfur dioxide on the respiratory system of Miyakejima adult residents 6 years after returning to the island

Abstract

Background: Mount Oyama, on the Japanese island of Miyakejima, began erupting in June 2000, necessitating the evacuation of 3,000 island residents. Volcanic gas emissions, primarily consisting of sulfur dioxide (SO₂), gradually decreased and residents returned to the island after the evacuation order was lifted in February 2005. Objectives: To assess the exposure-effect and exposure-response relationships between SO₂ exposure and effects on respiratory system in adult Miyakejima residents. Method: Health checkups focusing on pulmonary function and respiratory/irritative symptoms were conducted six times every November from 2006 to 2011. The study population comprised 168 subjects who underwent all health checkups. SO₂ concentrations were measured at six fixed monitoring stations in inhabitable areas. Result: Based on the annual mean SO₂ concentration, inhabitable areas were classified into three categories; namely, lower (L), higher (H-1), and highest (H-2) areas. Average SO₂ concentrations (ppb) during 3 months prior to each health checkup dropped from 11.3 to 3.29, 32.2 to 13.4 and 75.1 to 12.6 from 2006 to 2010/2011 in L, H-1, and H-2. No significant declines in pulmonary function were observed in all areas. However, prevalence of subjective symptoms such as "Cough," "Irritation and/or pain in throat," "Irritation, runny nose, and/or nasal sniffles," and "Irritation and/or pain in the eyes," dependently increased on SO₂ concentration. Odds ratios were statistically significant at approximately 70 ppb of SO₂ or above. Conclusion: Adult residents of Miyakejima island showed no deterioration in pulmonary function at SO₂ levels, but complained of respiratory/irritative symptoms in an SO₂ concentration-dependent manner.