Radon-222, a nobel gas, is odorless, colorless, water soluble, radioactive, and is the heaviest known gas. Its solubility in water is inversely proportional to water temperature. (Cross, 1990) Radon gas has a half-life of 3.8 days and is a decay product of radium, that begins with uranium-238. Uranium is abundant in granite, shale, and certain phosphates that are found in small amounts dispersed throughout the earth’s crust. Radon therefore may be found everywhere. Since it is a gas, radon filters through cracks in the bedrock and soil before it finally escapes into the atmosphere. When inhaled, radon gas flows quickly in and out of the lungs, but the formation of solid particles by radon poses the most serious problem as these tend to lodge in the bronchial tree. The particles can also damage the DNA which is found in all cells, and that damage can lead to uncontrollable cell reproduction which can cause the growth of a cancerous tumor. (Cole, 1993)
Studies have shown that the most significant factor in determining radon concentration was the geographical region, followed by the soil type, year of building construction, and type of building foundation. The lower figure represents a house with a basement, built in 1950’s on clay soil. The higher figure represents a house with a concrete slab in contact with the ground, built in the 1980’s on gravel. (Makelainen, 1990) This study shows that certain geographical regions and soil types with abundant granite, shale, and certain phosphates can have a high radon concentration. It also shows that houses built in 1950’s were usually less air tight which allowed a higher air exchange rate to get rid of radon gas. Additionally, a concrete slab foundation in contact with the ground will allow for more detrimental filtering of the radon gas.