Radon Elementi (İngilizce)
10.01.2009 17:19:51
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29 kez okundu.
Radon gas is a naturally occurring radioactive gas that is invisible and odorless. It forms from the radioactive decay of small amounts of uranium and thorium naturally present in rocks and soils so some radon exists in all rocks and soils. Certain rock types, such as black shales and certain igneous rocks, can have uranium and thorium in amounts higher than is typical for the earth�s crust. Increased amounts of radon will be generated in the subsurface at these locations. Because radon is a gas, it can easily move through soil and cracks in building slabs or basement walls and concentrate in a building�s indoor air. Areas with higher amounts of radon in the underlying rocks and soil are likely to have higher percentages of buildings with indoor radon levels in excess of U.S. Environmental Protection Agency guidelines, and incidences of very high indoor radon levels are more likely in these areas.
Breathing air with elevated levels of radon gas results in an increased risk of developing lung cancer. Radon-222 is the isotope of most concern to public health because it has a much longer half-life (3.8 days) than other radon isotopes (radon-219 at 4 seconds and radon 220 at 55.3 seconds). The longer half-life allows radon-222 to migrate farther through the soil, so much more radon-222 is usually available to enter buildings than any of the other radon isotopes. Not everyone exposed to radon will develop lung cancer, but U.S. EPA and the National Cancer Institute estimate the annual number of lung cancer deaths in the United States attributable to radon is between 7,000 and 30,000. The average concentration of radon in American homes is about 1.3 picocuries per liter and the average concentration in outdoor air is about 0.4 picocuries per liter. The U.S. EPA recommends that individuals avoid long-term exposures to radon concentrations above 4 picocuries per liter. The only way to know what the radon level is in a building or home is to test the air. Fortunately, radon testing is relatively simple and inexpensive. If indoor-air testing indicates radon levels exceeding 4 picocuries per liter, the U.S. EPA recommends remediation actions be considered.