Radon is continuously produced in the soil by the natural decay of uranium. It will typically move up into your home through cracks, holes, construction joints, cavities inside walls and utility entry points, etc. If left undisturbed, the radon gas remains in the soil and rapidly decays. However, the stack effect, (the tendency of air to rise in homes) causes a slight vacuum in the lowest level, which draws the radon from the soil into the home. All homes are subject to radon gas whether new or old, Testing is the only way to know how high the level is.
The normal outdoor radon level is about 0/4 picoCuries per liter (pCi/L), but because of the stack effect, the average nationwide indoor level is about 1.3 pCi/L. The EPA has established 4.0 pCi/L (more than 3 times normal) as the action level, the level at which action should be taken to reduce the indoor radon level.
Several published health studies demonstrate that when residential radon levels exceed 4.0 pCi/L, the incidence of lung cancer is increased. The increases become even more significant at higher radon levels.\\Nationwide, radon accounts for about 15,000-30,000 lung cancer deaths every year making it the second leading cause of lung cancer. The EPA estimates that only 6.7% of American homes have elevated radon levels (at or above 4.0- pCi/L). However studies by the American Lung Association of Eastern Missouri have revealed that about 20% of St. Louis area homes have elevated radon levels. This is about the same as the findings of the Missouri Department of Health/EPA study. Of 1987,88, which found elevated radon in 18% and 19% of Missouri homes.
