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Gifu's Hot Spring Museum! Episode 2: Definition of Therapeutic Hot Springs

In addition to the definition of hot springs by the Hot Springs Law, the Ministry of the Environment's "Guidelines for Hot Spring Analysis" based on the Hot Springs Law defines the conditions for "therapeutic hot springs" that are expected to be effective for treatment purposes.
According to this, if any one of the following conditions is met, it is recognized as a therapeutic hot spring that is expected to be effective for treatment purposes: 1. The temperature when collected from the hot spring source is 25°C or higher, 2. The dissolved substances excluding gas in 1kg of hot spring water are 1000mg (1g) or more, 3. Any one of the seven specified special components such as free carbon dioxide is contained in the specified amount or more.

Table 2 Definition of Therapeutic Hot Springs

Temperature (Temperature when collected from the hot spring source)	25°C or higher
Substance (Any one of the following)	Content per 1kg
・Total dissolved substances (excluding gaseous substances)	1000mg or more
・Free carbon dioxide (CO2)	1000mg or more
・Copper ion (Cu2＋)	1mg or more
・Total iron ion (Fe2＋＋ Fe3＋)	20mg or more
・Aluminum ion (Al3＋)	100mg or more
・Hydrogen ion (H＋)	1mg or more
・Total sulfur (S) (H2S＋HS－＋S2O32－)	2mg or more
・Radon (Rn)	111Bq or more

According to Table 2, seven types of substances are specified as special components, and the specified amounts are greater than those listed in the appendix of the Hot Springs Law, making it more difficult to be recognized as a "therapeutic hot spring" than as a "hot spring" under the Hot Springs Law. Therefore, there are hot springs that are recognized as "hot springs" under the Hot Springs Law but do not meet the definition of "therapeutic hot springs".
Even if it is recognized as a "hot spring" by meeting the conditions of the Hot Springs Law, it will not be given a "spring quality name" unless it meets the conditions of a therapeutic hot spring. A spring quality name is a name such as "simple hot spring" or "sulfur spring" that is given according to the characteristics of the hot spring's quality.
The notation method for spring quality names is determined in the Guidelines for Hot Spring Analysis, and it is mandatory to use that spring quality name. Often, in hot spring guides or pamphlets, you may see unique notations such as "simple spring", "meta-silicic acid spring", "iodine spring", "boric acid spring", "alkaline spring", but these are not official spring quality names.
For hot springs that meet the conditions of the Hot Springs Law and are recognized as "hot springs" but do not meet the conditions of therapeutic hot springs, they are labeled as "Hot Springs Law Article 2 applicable hot spring", "Hot spring corresponding to the Hot Springs Law by the value of meta-silicic acid", etc.
Furthermore, only when the conditions of a therapeutic hot spring are met, the display of indications (symptoms for which effects can be expected) and contraindications (symptoms for which bathing or drinking the hot spring is not allowed) is permitted.