Radon
Radon is a colorless, odorless and tasteless radioactive gas that occurs naturally in most rocks and soil. It is produced by the breakdown of uranium in soil, rock and water. Radon is harmlessly dispersed in outdoor air, but when trapped in buildings can increase the risk of lung cancer, especially at elevated levels. It typically enters a home the same way air and other soil gases enter the home, through cracks in the foundation, floor or walls, hollow-block walls and openings around pipes, sump pumps and floor drains. It can also be present in some construction materials and in water from underground sources including private wells.
Radon is a radioactive gas that is known to occur in Interior Alaska, especially in the hills around Fairbanks. Radon gas is only a problem when it is trapped in spaces where people live and work. Radon mitigation is most effective during initial home construction but can be retrofitted in many circumstances. Since radon was first found to be a concern in Alaska in 1986, the interest and awareness of radon as a special housing and health problem has continued to grow. Below is a map that indicates the areas in Alaska most at risk for radon problems. This map and accompanying documents can be found at http://www.uaf.edu.
Efforts at mitigation are being made that have been most effective in reducing radon under Alaska conditions. Clearly, radon must be able to enter a home in order to be a problem and four factors must exist in a house’s location for it to be a radon “at risk” home. Two of the factors are geological in nature; the other two factors are determined by the structure of the house itself and the way it is operated. Of the four criteria that have been identified the absence of any single one of these characteristics generally eliminates the possibility of radon.
1. There must be adequate uranium to provide a source for radon transport;
2. There must be enough permeability in the soil to allow rapid soil gas movement to carry radon from its origin to the interior of the home;
3. The house must have soil contact that has imperfections, holes, cracks, or intentional perforations which allow the movement of radon through the basement or crawl space;
4. There must be lower pressure inside the house than in the soil so that radon flows into the house.
During two years of testing by the University of Alaska, it became clear that Interior Alaska,especially the uplands near Fairbanks, is a radon risk area. In the first year of radon screening tests, done non-randomly with Air-Check brand charcoal screening kits, 52 % of the 353 tests were at or above the remedial action level as set by the Environmental Protection Agency (EPA). More than 20% of the tests, or one in five,were above 20 pCi/l (pico Curies/liter), which is five times the EPA recommended remedial action level.
It was determined after initial testing that Fairbanks needed further research to determine how significant the radon problem was in homes. The researchers also wanted to identify means of mitigation. They felt that because of the long heating season in Fairbanks, a factor in radon transport, testing throughout the heating season using oil-fired combustion systems, would give them further data. This type of heating system actually provides the negative pressure to move radon into the house and causes radon concentrations to rise. The heating systems in houses can tend to act as a pump that sucks radon laden air into the bottom of the house, and drives the exhaust out the top.
All of these factors relate to an understanding of the problem in a specific geological setting. This does not mean that radon cannot be present in areas which are less suspect, such as flood plains, highly porous gravel in valleys or deep silts. As you can see on the following map from the US EPA, there is potential for other areas in Alaska to have radon issues but the chances of radon in homes is less that in the Fairbanks and Mat-Su regions.
Zone 1 communities (Red Zone) have a predicted average indoor radon screening level greater than 4 pCi/L (pico curies per liter) Highest Potential
Zone 2 communities (Orange Zone) have a predicted average indoor radon screening level between 2 and 4 pCi/L Moderate Potential
Zone 3 communities (Yellow Zone) have a predicted average indoor radon screening level less than 2 pCi/L Low Potential
During the analysis there was radon located where it was not expected. One such area was the Aurora Subdivision in Fairbanks, another was Lakloey Hill on Badger Road in the North Pole. The Lakloey Hill situation was a model of the larger hills to the north of Fairbanks, so it was more explainable than the Aurora Subdivision case. The somewhat alarming experience early in Fairbanks led ultimately to Alaska’s inclusion in the third round of EPA’s Ten State Surveys. The Alaska EPA/DGGS (U.S. Environmental Protection Agency/Alaska Division of Geological and Geophysical Surveys) survey was completed in the spring of 1989 and the results explained, among other revelations, the conditions in Fairbanks uplands which constituted and still do constitute an “at risk” home.
- The homes are built high on a hill slope with bedrock consisting of Birch Creek Schist “Schist “is defined by Wikipedia as group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others.
- The top soil depth less than the basement excavation (eight feet or less)
- The standard basement construction for daylight basement notched into a hill
- The home had an oil-fired combustion heating system
- Basement material either concrete or All-Weather Wood (AWW)
Any house on a similar site with these conditions and construction styles should be tested for radon. Along with the confirmation of these radon risk characteristics, the Alaska EPA survey found that:
Interior Alaska has the highest proportion of homes with elevated radon concentrations as well as the individual homes with highest concentrations. In the Interior, 3% of homes within the sample population had screening levels higher than 20 pCi/l and 17.6% of homes had radon screening levels that were higher than 4 pCi/l. 30 to 35% of homes built in the hills around Fairbanks have elevated radon concentrations.
CASE STUDIES:
Homes built in the surrounding hills of Fairbanks, with concrete slabs or basements directly in contact with bedrock yielded the highest radon screening levels. Many of the homes without elevated radon levels were built on hillside sites and included homes which were built on thick accumulation of windblown glacial silt (loess). Thick accumulations of loess or virgin organic material rather than shale or rock fill, appear to be an effective barrier to radon movement. Homes built on alluvium from the Tanana and Chena Rivers are also much less at risk.
High radon concentrations in homes in contact with bedrock are likely to result from high fracture permeability of the bedrock as well as relatively high uranium concentrations in the schist which comprises local bedrock. Low radon concentrations in homes built on loess and alluvium may reflect low soil gas permeability, low uranium concentrations of soils, or both.
Strategies for Mitigation
With the research findings and information on at-risk sites, it is possible to pursue a strategy for mitigation. Based on the conditions previously cited for “at-risk” homes, this can provide a series of options for radon mitigation, since elimination of any of the four characteristics will achieve mitigation. The two geological conditions, uranium presence and permeability, are fixed at a home site. Removing either of these conditions would be expensive as well as impractical. Therefore, the other two conditions, which are structural, leakiness and pressure difference, can be the practical candidates for mitigation.Solutions can be sealing the basement or crawl space, and/or change the pressure differential. A review of EPA mitigation literature shows combinations of these two methods as the most common approach. The Alaska experience concurs, with more reliable results from sub-slab ventilation than from just sealing leaks. Recent surveys show that, in all but one case, sub-slab depressurization accompanied by sealing leaks in the basement or crawl space, was the most successful mitigation technique.
There are climatic as well as geologic reasons why sub-slab depressurization works as opposed to overpressurizing the slab or house interior. While it may be physically logical to overpressurize the interior of a home to exclude radon, this strategy also drives warm, moist, interior air out of all of the nooks, crannies, keyholes and doorsills. At very cold temperatures, an overpressurized system would freeze doors and windows shut. This is obviously an unacceptable alternative.
Sub-slab depressurization is presently the only option with a consistently high success rate according to the Fairbanks findings.. New construction on radon-suspect sites has been tried with mixed success.
Find more information on Radon at the following website: http://www.uaf.edu/ces/faculty/seifert/energy.html
Health Effects of Radon
While most people are aware that air pollution can be hazardous to their health, many do not know that the air they breathe inside their own homes could be killing them. Millions of homes and buildings contain high levels of radon gas. Many do not even know it is present. When radon decays and is inhaled into the lungs, it releases energy that can damage the DNA in sensitive lung tissue and lead to lung cancer. Short-term exposure to radon causes no immediate symptoms, prolonged exposure to high levels of radon is the second leading cause of lung cancer in the United States, contributing to between 7,000 and 30,000 lung cancer deaths each year. Radon is the number one cause of lung cancer among non-smokers, according to EPA estimates. Overall, radon is the second leading cause of lung cancer. About 2,900 of these deaths occur among people who have never smoked. Smokers are at higher risk of developing radon-induced lung cancer because of the combined effects of radon and smoking. For smokers about 62 people in a 1,000 will die of lung-cancer, compared to 7.3 people in a 1,000 for people who never smoked. Put another way, a person who never smoked who is exposed to 1.3 pCi/L has a 1 in 500 chance of lung cancer; while a smoker exposed to the same amount of radon has a 1 in 50 chance of dying from lung cancer.On January 13, 2005, Dr. Richard H. Carmona, the U.S. Surgeon General, issued a national health advisory on radon. Visit http://www.cheec.uiowa.edu/ for more on a study by Dr. William Field on radon-related lung cancer in women.
To learn more about lung cancer, the following sources provide a wide range of good information about lung cancer, prevention, and treatment.
American Cancer Society -- http://www.cancer.org/docroot/home/index.asp
American Lung Association -- http://www.lungusa.org/
National Cancer Institute -- http://www.cancer.gov/
Vanderbilt-Ingram Cancer Center -- http://www.vicc.org/
Memorial Sloan-Kettering -- http://www.mskcc.org/mskcc/html/44.cfm
The World Health Organization (WHO) says radon causes up to 15% of lung cancers worldwide. In an effort to reduce the rate of lung cancer around the world, the World Health Organization (WHO) launched an international radon project to help countries increase awareness, collect data and encourage action to reduce radon-related risks.
The radon health risk is underscored by the fact that in 1988 Congress added Title III on Indoor Radon Abatement to the Toxic Substances Control Act. The ACT was codified and Congress funded EPA’s then fledgling radon program. Also that year, the Office of the U.S. Surgeon General issued a warning about radon urging Americans to test their homes and to reduce the radon level when necessary.
The U.S. Surgeon General and EPA continues to recommend that all homes be tested. You can test your home yourself or speak with your tribal housing or air quality professional. You may be able to fix your home if you have a radon level of 4 pCi/L or more. If your community does not have free radon kits, you can get discounted radon test kits from the National Safety Council (or call 1-800-SOS-RADON). Some home improvement stores sell test kits. If you are in an area with identified high radon levels, you can find a qualified testing or mitigation contractor by contacting your state radon office.
The US EPA has, in the past, provided Tribal funds for testing programs in Tribal communities that may be affected. Contact Region 10 EPA for information on the State and Tribal Indoor Radon Grant (SIRG) for more information, or you can find more information at the following website: http://epa.gov/radon/sirgprogram.html.
The Alaska Radon Program can be contacted at:
Radiological Health Program
Section of Laboratories
4500 Boniface Parkway
Anchorage, AK 99507-1270
Radon Contact: Richard Seifert ffrds@uaf.edu
Radon Hotline at University of Alaska Cooperative Extension:
1-800-478-8324/(907) 474-7201