Radon
1/31/2011
It was not that long ago: 1986, when a construction engineer at the Limerick Nuclear Power Generating Station in Pottstown, Pa. visited the plant’s radiation-detection section. When he stepped into the radiation counting machines, his radiation levels were so high that the monitors hit overload and could not properly function. A survey showed that every part of his body was contaminated by radiation. This was shocking, especially as he didn’t work directly with radiation.
When the engineer’s house was examined it was discovered that radon gas was present in very high airborne concentrations. Indeed, his basement tested at a phenomenal 2700 picocuries per liter (pci/l). That’s the equivalent of smoking 135 packs of cigarettes a day. Thus began a national awareness and concern for radon.
Today, The U.S. Environmental Protection Agency (US EPA) and the Surgeon General’s Office have estimated that as many as 20,000 lung cancer deaths are caused each year by radon, making it the second leading cause of lung cancer. Radon-induced lung cancer costs the United States over $2 billion dollars per year in both direct and indirect health care costs. According to the US EPA, many homes have been assessed with radon levels that exceed the EPA residential screening level of 4 pCi/l: this is approximately 35 times as much radiation as the Nuclear Regulatory Commission would allow if that family was located next to the fence of a radioactive waste site.
Radon a naturally occurring element listed on the periodic table of elements; symbol Rn and atomic number 86. It is a colorless, odorless, tasteless noble gas, occurring naturally as the decay product of radium (ra-226) within the decay chain of uranium 238 (the isotope that contributes to depleted-uranium sources or “non-enriched”). While radon is one of the densest substances, it remains a gas under normal conditions and is considered to be a health hazard not only because it is a radioactive material, but because it is a gas and, therefore has the ability to transfer from inside walls or underground locations by seeping through cracks, fissures, crevices and underground pipes into spaces that are occupied by people, who then may inhale the gas due to its airborne properties.
While radon does occur in a number of forms (isotopes) it’s most stable isotope is 222Rn and has a half-life of 3.82 days. This means that ½ of the radon present during an initial count, would be decayed into other materials (referred to as progeny) within 3.82 days. All radon forms are alpha emitters, and therefore, as with all alpha emitters, there is a health concern due to inhalation.
Yet, it is really not the exposure to radon that poses this health risk to humans; rather it is its decay progeny. These isotopes, such as 218Polonium, 214Lead, 214Bismuth, and 214Polonium, have extremely short half-lives ranging from fractions of a millisecond to less than ½-hour. Therefore, once radon gas has entered into the lungs, these progeny will rapidly decay and release energy: such energy that can cause molecular ionization to various biologic systems, including cellular and molecular structures such as DNA, as well as creating free radicals: one of the current theories associated with the initiation of cancerous tissue.
Because radon is part of the normal radioactive decay chain of U-238, which has an extremely long half-life (approximately 4.5 billion years – since the earth was formed), uranium, radium, and thus radon, will continue to occur for millions of years at about the same concentrations as they do now.
Although radon, per se, was not specifically identified as a health hazard in mines in ancient times, it was known for centuries that an inhalation hazard causing serious respiratory illnesses to miners existed. It wasn’t until the twentieth century that we understood that such illnesses could be attributed to high radon concentrations, where exposures reaching 1,000,000 Becquerels per cubic meter were measured. In 1530, Paracelsus described a wasting disease of miners, the mala metallorum, and Georg Agricola recommended ventilation in mines to avoid this mountain sickness (Bergsucht). In 1879, this condition was identified as lung cancer by Herting and Hesse in their investigation of miners from Schneeberg, Germany. The first major studies with radon and health occurred in the context of uranium mining, first in the Joachimsthal region of Bohemia and then in the Southwestern United States during the early Cold War.
The highest average radon concentrations in the United States are found in Iowa and in the Appalachian Mountain areas in southeastern Pennsylvania. Iowa has the highest average radon concentrations in the United States due to significant glaciation that ground the granitic rocks from the Canadian Shield and deposited it as soils making up the rich Iowa farmland. Many cities within the state, such as Iowa City, have passed requirements for radon-resistant construction in new homes. In a few locations, uranium tailings have been used for landfills and were subsequently built on; resulting in potential increased radon exposure.
Radon is responsible for the majority of the public exposure to ionizing radiation. It is often the single largest contributor to an individual’s background radiation dose, and is the most variable from location to location. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as attics, and basements. It can also be found in some spring waters and hot springs. Radon is considered a significant contaminant that affects indoor air quality worldwide.
Testing for radon in your home can be quite simple. The EPA has a wealth of information which can be accessed through internet sites, such as, http://www.epa.gov/radon/pubs/citguide.html#howtotest (EPA’s “A Citizen’s Guide to Radon”). Test kits can be obtained that are inexpensive and easy to use. The EPA also has guidelines on controlling and mitigating radon gas build-up. Solutions can be as simple as filling in cracks and crevices in your basement (where radon is most likely to accumulate) or increasing ventilation. Today, homes built in areas where there is a potential radon problem can be constructed with a number of “radon reduction” features. These include active soil depressurization (ASD), and sub-slab depressurization (SSD) systems. These systems work by changing air pressure beneath your home and then, through the use of a specially designed radon fan, drawing out and safely venting it, through one or more pipes, above the roofline,
The highest average radon concentrations in the United States are found in Iowa and in the Appalachian Mountain areas in southeastern Pennsylvania. Iowa has the highest average radon concentrations in the United States due to significant glaciation that ground the granitic rocks from the Canadian Shield and deposited it as soils making up the rich Iowa farmland. Many cities within the state, such as Iowa City, have passed requirements for radon-resistant construction in new homes. In a few locations, uranium tailings have been used for landfills and were subsequently built on; resulting in potential increased radon exposure.
Radon is responsible for the majority of the public exposure to ionizing radiation. It is often the single largest contributor to an individual’s background radiation dose, and is the most variable from location to location. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as attics, and basements. It can also be found in some spring waters and hot springs. Radon is considered a significant contaminant that affects indoor air quality worldwide.
Testing for radon in your home can be quite simple. The EPA has a wealth of information which can be accessed through internet sites, such as, http://www.epa.gov/radon/pubs/citguide.html#howtotest (EPA’s “A Citizen’s Guide to Radon”). Test kits can be obtained that are inexpensive and easy to use. The EPA also has guidelines on controlling and mitigating radon gas build-up. Solutions can be as simple as filling in cracks and crevices in your basement (where radon is most likely to accumulate) or increasing ventilation. Today, homes built in areas where there is a potential radon problem can be constructed with a number of “radon reduction” features. These include active soil depressurization (ASD), and sub-slab depressurization (SSD) systems. These systems work by changing air pressure beneath your home and then, through the use of a specially designed radon fan, drawing out and safely venting it, through one or more pipes, above the roofline,
Most U.S. EPA lifetime safety standards for carcinogens are established based on a 1 in 100,000 risk of death. Most scientists agree that the risk of death for radon at 4 pCi/l is approximately 1 in 100. At the 4 pCi/l EPA action guideline level, radon carries approximately 1000 times the risk of death as any other EPA carcinogen. It is important to note that the action level is not a safe level, as there are no “safe” levels of radon gas.
Our life’s a stage, a comedy: either learn to play and take it lightly, or bear its troubles patiently.
Palladas (4th Century Greek Poet: lived in Alexandria, Egypt)