IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

1W_4F-P7

Date/Time: July 21 Poster

Effects of SO 2 on the respiratory system in Miyakejima residents seven years after
returning to the island
Satoko Iwasawa1 , Tazuru Tsuboi1 , Takeshi Kochi1 , Makiko Nakano1 , Takamoto Uemura2 , Shigeru
Tanaka3 , Kazuyuki Omae1
1Keio University, Japan, 2 Kyorin University, Japan, 3 Jumonji University, Japan
E-mail: iwasawa@a5.keio.jp

Background: Miyakejima Island is an island volcano 8 km in diameter, located 180 km south-southwest of Tokyo. In
the last 500 years, Mt. Oyama has erupted repeatedly every 50 years. The last eruption started in June, 2000, anddue to continuous eruptions and emissions of lethal/unsafe amounts of volcanic gas, the Miyake village government
decided to evacuate all the citizens from the island in September, 2000. At the time of the evacuation, the amountof discharge of sulfur dioxide (SO 2 ), the major toxic component of the volcanic gas, was 50,000 tons/day. Thevolcanic activity gradually decreased, but it has not ceased, and SO 2 discharge of 400 - 700 tons/day continues tobe observed as of January, 2013. In February, 2005, citizens began to return to live on the island despite the factthat volcanic gas was still being emitted.
Objectives: In this study, the health effects of exposure to the environment on Miyakejima Island following the liftingof the evacuation order in February, 2005, were investigated, first in February, 2006, and then in each November
from 2006 to 2011. The relationship between the amount of exposure to SO 2 and health effects was studied in
Miyakejima residents.
Method: The subjects of this study were registered residents of Miyakejima. A total of 4,089 check-ups for adults
and 1,005 check-ups for children were conducted. The mean values and percentages hourly values of 0.10 ppm or
more were obtained from 81 months of exposure concentration data obtained by fixed-point monitoring. Based onthese values, we used averages to categorize the inhabited area into 1 lower-SO 2 area and 2 higher-SO 2 areas,
namely, the Izu and Kamitsuki districts, referred to as Area L, the Igaya and Tsubota districts, referred to as Area
H-1, and the Ako district, referred to as Area H-2. Health effects were evaluated through pulmonary function tests.
Results: The average SO 2 concentrations in Areas L, H-1, and H-2 were 4.57, 18.9, and 26.1 ppb, respectively.
The rates at which the one-hour average SO 2 concentrations exceeded 0.1 ppm in Areas L, H-1, and H-2 were1.35, 4.16, and 5.80 %, respectively. The Air Quality Standard of SO 2 in Japan is 0.04 ppm or below for the daily
average of one-hour SO 2 concentrations and 0.1 ppm or below for the one-hour SO 2 concentration. The island asa whole has not yet achieved the standard.
In adult Miyakejima residents, there were significant differences in the %FVC and %FEV1 values observed in acomparison of pulmonary function by area. However, no significant difference was observed in a comparison overtime. By contrast, children showed no reduction in lung function.
Conclusions: Follow-up observation should be continued with a focus on the relationship between the amount of
exposure to SO 2 and health effects until the volcanic gas emissions have ceased.

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