In the European countries of advanced balneology, the hot spring treatments based on scientific grounds are provided widely in the hot spring hospitals and medical facilities under medical doctors. On the other, in our country the hot springs are mainly utilized as the source of “a feeling” such as hot spring cure, sightseeing, or leisure, but not used as a complementary treatment to modern medicine in order to enhance our health.
The Izu Peninsula, a very limited area of Japan, consists of various strata due to the submarine volcanoes, the land volcanoes and the simple volcanoes. Those strata are distributed over the Izu Peninsula like a mosaic, and there are many hot springs on each stratum. Since such a place is very rare in the world, the Izu Peninsula is thought to be the most suitable place to investigate various hot springs scientifically.
Thus I visited these spring resorts, obtained a hot spring analysis book (onsenbunsekisho) from each hot spring facility and clarified the characteristics of each hot spring based on the information from its analysis book. The present study shows that there are three kinds of hot springs in the Izu Peninsula: sulfate springs, chloride springs and simple hot springs.
The origin of the sulfate springs in the old strata of Nishi-Izu and Naka-Izu is mainly due to the green tuff produced from the submarine volcanoes. The densities of sulfate ions in these springs are very high, suggesting their high pharmacological effects on several medical symptoms.
In addition, the chloride springs in Mimami-Izu are hypertonic due to highly concentrated sodium ions, calcium ions and chloride ions, and thus expected to have detox effects on radioactive materials such as cesium 137 and strontium 90 by bathing in this type of spring.
The simple hot springs in Nishi-Izu and Naka-Izu have the property of a sulfate spring, those in Higashi-Izu have the properties of sulfate and chloride springs, but those in Minami-Izu have many properties due to various negative ions such as hydrogen carbonate and carbonate.
The future research themes for the establishment of balneology by using the hot springs in the Izu Peninsula are as follows:
(1) Comparison of the chemical ingredients in the hot spring source water with those in its corresponding bathtub water; to examine changes in the physical and chemical properties of the water during the water-supply process.
(2) Quantitative analyses of mineral components in the hot spring waters suited for drinking use; to find out existing amounts of the minerals in the antioxidant enzymes, and those of the minerals scarce in everyday life.
(3) Establishment of indexes of the pharmacological effects of the sulfate springs by using laboratory animals or iPS cells; to evaluate scientifically the effects of the anions and cations in the sulfate springs on the animals or the cells.
(4) Examination of the detox effect from bathing in the hypertonic chloride spring on cesium 137 and strontium 90; to find out the possibility of reducing the radiation exposure of the people exposed to the Fukushima nuclear power plant accident.
(5) Examination of the protective effect of bathing in the simple hot springs on medical exposure disorders; to find out the possibility of preventing and mitigating the medical exposure disorders of exposed patients through radiation diagnosis and therapy.