Cancer Mortality Studies in Misara, a Radon Hot Spring in Japan: A Summary up to 2003

ABSTRACT

Misasa, which is well known for its radon hot springs, is a historical town located in Tottori Prefecture, Japan. The presence of the hot springs is noted in an 1164 entry in town records. The presence of radioactivity in the hot springs was recognized in 1914. Since ancient times, the spring water has been believed to be healthful. The town of Misasa has 90 radon hot spring sources, yielding a total volume of 3,000 tons of spring water a day. The concentration of ²²²Rn in the spring water ranges from 17.4 to 9,361 Bq per liter. A series of cancer mortality studies on the radon hot springs were conducted through the collaboration of scientists scattered throughout different Japanese cities. At present, no definite evidence has been discovered that indicates an increase of cancer mortality in the Misasa radon hot spring area. Even a lower risk was found for stomach cancers in both radon and no-radon hot springs.

Keywords:

• radon
• hot springs
• cancer studies
• drinking water.

ACKNOWLEDGMENTS

We thank Dr. Masaaki Mifune for his all efforts to have made the cancer mortality studies in Misasa possible. We are grateful to Dr. Sohei Kondo for his stimulating discussions in initiating these studies and to all of our collaborators. A series of the studies was supported by grants-in-aids for cancer research from the then Ministry of Health and Welfare, Japan.