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Radon [Rn, 88]
In view of the latest scientific data, the World Health Organization (WHO) proposes a reference level of 100 Bq/m 3 to minimize health hazards due to indoor Rn
exposure. However, if this level cannot be reached, under the prevailing countryspecific conditions, the reference level should not exceed 300  Bq/m 3 , which represents approximately 10 mSv per year, according to recent calculations by the
International Commission on Radiological Protection (WHO 2009).
Radon is used in the medical field. Archeological discoveries in the Central and
Southern Europe suggest that therapeutic properties of certain waters were well recognized in ancient times, but only within the last century high concentrations of Rn
were discovered to be present in these waters. Radon spas are used extensively in the
Southern and Central Europe and Japan, to treat several health conditions (WHO
2009).
The therapeutic use of Rn involves the intake of Rn gas either through inhalation
or by transcutaneous resorption of Rn dissolved in water. Mineral Rn water is used
in the treatment and rehabilitation of chronic inflammatory and degenerative rheumatic diseases, neurological diseases, cardiovascular diseases, allergic disorders,
gynecological disorders, and endocrine and vegetative disorders.
The exact mechanism of the effect of Rn on the human body is not completely
understood. The hormesis theory (a metal or ionizing radiation that produces harmful biological effects at moderate to high doses may produce beneficial effects at
low doses) is the best explanation of the advantageous biological effect of ionizing
radiation in low doses (Zdrojewicz and Strzelczyk 2006). Radon therapy is not an
approved biomedical therapy in the United States, primarily due to continuing controversy over how much Rn exposure is safe (Erickson 2007).