Radon [Rn, 88]

Radon is easily released from granitic soils to the atmosphere, which is estimated, on a global scale, to be 2400 mCi annually. Radon may migrate freely through faults and fragmented soils, and may accumulate in caves or water. Radon concentrations in groundwaters vary from 1 to 50 Bq/L for rock aquifers in sedimentary rocks, from 10 to 300 Bq/L for wells dug in soil, and from 100 to 50,000 Bq/L in crystalline rocks. The highest contents are usually associated with high U concentrations in the bedrock. Significant seasonal variations in concentrations have also been observed. Radon and its decay products are carcinogenic to humans. Radon spas are used extensively in the Southern and Central Europe and Japan, to treat several health conditions. The therapeutic use of Radon involves the intake of Radon gas either through inhalation or by transcutaneous resorption of Radon dissolved in water.