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No more than four (4 pCi/L)!
The average indoor radon level is estimated to be about 1.3 pCi/L and about 0.4 pCi/L of radon is normally found in the outside air. Most homes today can be reduced to 2 pCi/L.
Each year, it is estimated that radon causes about 21,000 lung cancer deaths per year, according to EPA’s 2003 Assessment of Risks from Radon in Homes (EPA 402-R-03-003). It’s found naturally in the ground and seeps through cracks or holes in the foundation and become trapped in your home.
The Discovery of Radon in Homes
In 1984, the scientific world woke up to the existence of radon in homes. A construction engineer triggered radiation alarms while entering the Limerick nuclear power plant near Philadelphia. His home in Boyertown was tested and the radon concentration was a shocking 2,700 pCi/L.
The family, including small children, was immediately evacuated. Very high radon levels were also found in nearby houses. This region, known as the Reading Prong, has low-grade uranium deposits and encompasses parts of Pennsylvania, New Jersey, and New York.
There are relatively simple tests for radon gas, but these tests are not commonly done, even in areas of known systematic hazards. Home radon test kits are widely available and can be found at your local Walmart, Target, or hardware store. The short-term radon test kits used for screening purposes are inexpensive (under $15) and some states offer home test for free. The kit includes a collector that the user hangs in the lowest livable floor of the home for 2 to 7 days. The user then sends the collector to a laboratory for analysis.
If your home radon kits result is 4 pCi/L or higher you should contact your state radon office and schedule a follow-up long-term test for a better understanding of your year-round average radon level.
If you followed up with a long-term test and the results are 4 pCi/L or more, you should fix your home.
The five principal ways of reducing the amount of radon accumulating in a home are:
The half-life for radon is 3.8 days, indicating that once the source is removed, the hazard will be greatly reduced within a few weeks.
Workers entering the Super Collider at the Argonne National Laboratory near Chicago used to trigger radioactivity alarms when it rained. It was discovered that rainwater deposited on their shoes and hands carried radioactive decay products of radon. The laboratory developed special radiation monitors to detect the specific gamma rays emitted by radon progeny in rain clouds. During the first year of operation the alarm was triggered nine times. Since the radon alarms occurred simultaneously at two monitors approximately 1,000 meters apart, it proved that large radon-saturated clouds are regularly passing over populated areas. It confirmed that radon released by wastes from uranium mines in the West can travel hundreds of miles across America.
Source: Health Physics, November 1999
Radium Dial Painters
Shortly after its discovery radium was used to make luminous paints. During World War I, hundreds of young women in New York and Illinois were applying the highly radioactive paint to aircraft instrument dials. Radium painting expanded to “glow-in-the-dark” clocks and watches.
The young women who applied the paint frequently licked the brush to keep it pointed and their work area was saturated in radon. Suspicions arose in the late 1920′s over jaw cancers among the dial painters, as their tragic saga slowly started to unfold. Initially, the plant managers accused the women of bad hygiene. Years later, most of these women died of cancer.
During World War II, young women painted radium on military instruments, so that the dials would glow in the darkness of a cockpit. Precautions were now taken to avoid the ingestion of radium, but the danger of the released radon gas was not understood. Cancer has killed many of these women during the following 20-30 years.
Since the mid 1960′s, watch manufacturers are using Tritium, a radioactive form of hydrogen with a half-life of 12 years, or Promethium, a man-made radioactive element with a half-life of 2.6 years. Both of these elements are weak beta and gamma emitters but only few of the particles penetrate the cover glass of the watch.
Center for Nuclear Science and Technology Information of the American Nuclear Society
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