Radon is an invisible and odorless radioactive gas and is continuously created by natural breakdown metals in soils. Any home in any state may have a radon problem. The average person receives each year more radiation from radon than from all other source. Almost all risks come from breathing air with radon and its decayed products.
The collection of deadly radon gas is an environmental hazard associated with areas of karst topography. Radon gas is a known cause of lung cancer. Many areas with karst bedrock are composed of limestone. Phosphate minerals that occur naturally in limestone contain small amounts of uranium. Uranium is a radioactive, toxic element which is easily oxidized. As a result of the uranium degrading into lead, small amounts of radon are produced as a byproduct. Over a period of time, this radon gas can accumulate within solution-derived karst cavities or in naturally occuring joints in the bedrock.
Structures built above karst cavities are prone to infiltration of radon due to fluctuations in atmospheric pressure (Ruthven, C. et. el., 2002). Also, it is believed that considerable amounts of radon are produced with in the soils overlying karst bedrock. This radon is thought to be released into water reservoirs beneath the surface following heavy rain events (Savoy, L. et el,)
Air pressure inside homes (basements) is slightly lower than in the ground creating a vacuum which draws in radon from several feet away into the basement through openings and pores in concrete. Warm air inside homes moves upward like inside a stack and this stack effect reduces air pressure in the basement. When the ground is soaked with rain, the bottled up radon gas in the ground moves to a warm opening such as a basement. This stack effect will cause radon inflow that will easily migrate in to the home.
Almost half of the water used in poured concrete mix is surplus and has to evaporate. Concrete cures and passes moisture to the surfaces creating a network of capillaries (pores). The pores allow a passage way for radon gases, water vapor, and liquid water to enter the basement.
Heavy radon gas accumulates in basements and on lower floors. According to the residential radon lung cancer study completed in Iowa, the 1st floor of a home receives 40% of its air from the basement level.
Radon gas in groundwater seeping through your leaking basement wall and floor because of hydrostatic pressure causing a wet basement can be harmful to your health. Radon decaying products causes cancer. It is estimated that 12% of all lung cancers are caused by exposure to Radon gas. It is also estimated that 15,000 to 20,000 of the 158,000 lung cancer deaths per year in the United States are caused by exposure to Radon. Many years may pass before the effects of radon are detected.
Household radon test kits are readily available and fairly inexpensive. They are easy to use and the results are easy to evalute. Levels registering greater than 4.0 picocuries are cause for concearn. If you find yourself in this category, the EPA recommends actions be taken to improve the conditions within your residence such as allowing for more ventilation of basements and crawlspaces in the house, as well as sealing crawl spaces with plastic. Also, these potential geologic hazards can be identified by geologists in order to mitigate the risks that are presented by the karst bedrock.
Radon infiltration is a problem to be taken seriously. Prolonged exposure to the gas can result in serious health problems and even death. If you believe you may have radon infiltration problems, here is a link that may help you:
Free radon testing kits through the EPA: - http://www.free-radon-test-kits.com/