|
|
LAWRENCE HALL OF SCIENCE STUDENT RADON RESEARCH PROJECT |
|
Radon is an important terrestrial gas whose presence and concentration are easy (and fairly inexpensive) to detect. Being an inert gas, the behavior of radon is far more affected by physical conditions in the environment than by chemical processes that affect other terrestrial gases. Consequently, radon concentration levels are strongly affected by geological and geophysical conditions, as well as atmospheric influences such as barometric pressure and rainfall.
Formed as a result of radioactive decay of the element uranium, radon is a colorless and odorless radioactive gas that is fairly abundant. Movement of radon through the earth is strongly influenced by moisture content and permeability of soil, porosity and degree of fracturing in rocks, as well as surface meteorological conditions. As a result, the ease with which radon moves in pore spaces or fractures affects how much radon reaches the earth's surface at any given location. Thus anomalously high concentrations of radon are often found in soils above highly fractured rock such as that associated with geologic faults and active volcanoes.
Investigations throughout the world over the past 15 years provide evidence which indicates that significant variations of radon concentration may occur in association with major geophysical events such as earthquakes and volcanic eruptions (Virk and Singh, 1993; Heiligmann et al., 1997). Thus, it has become clear that investigations of radon's behavior can generate valuable information useful in the study of tectonic activity within the earth's crust. As a result, radon emanation studies are currently underway in several tectonically active regions on Earth, such as Central America and Mexico (J.L.Seidel, 1996), China (Linpei, 1994), and Japan (Igarashi et al., 1995). These programs are designed to provide information needed to develop a sound understanding of mechanisms responsible for observed variations in radon concentration. Before information derived from such programs can truly contribute to a greater understanding of geophysical activity on Earth, however, non-tectonic influences on radon emanation must also be closely examined and thoroughly analyzed (King, 1986).
Radon moving through soil pore spaces and rock fractures near the surface of the earth usually escapes into the atmosphere. Where a house or other building is present, however, radon may migrate into these structures, and accumulate indoors in sufficient quantities to pose a health hazard. The potential hazard of prolonged exposure to radon gas and its daughter products has become a matter of great concern in recent years. A substantial amount of material has been published in the scientific literature derived from studies dealing with the issue of human risk from exposure to radon (e.g.Neuberger, 1993; and Stidley and Samet, 1993), as well as, in publications by the US Environmental Protection Agency (EPA), the Department of Energy (DOE), and the National Academy of Sciences (NAS). The largest study was an international one conducted by the National Cancer Institute (NCI), which examined data on 68,000 underground miners who were exposed to a wide range of radon levels.
Although the international scientific community continues to conduct research to refine our understanding of the precise nature of health risks associated with exposure to radon gas, an extensive body of epidemiological evidence examined by health and medical scientists throughout the world indicates that it is a human lung carcinogen. In fact, the US Surgeon General has warned that radon is the second leading cause of lung cancer in the United States (EPA, 1993), and a recent report published by the National Research Council estimates that between 15,000 and 21,000 deaths each year are the result of long-term exposure to radon (Samet et al, 1998).
High levels of radon have been discovered in homes in every state, and found in more than 70,000 schools in use today across the country. A nationwide survey of radon levels indicates that nearly one in five schools has at least one classroom with high radon levels (EPA, 1994). Studies of radon's behavior in the geological environment suggest that a direct relationship exists between indoor levels of radon and the concentration of the gas in soil (Ball et al., 1991; Shirav and Vulkan, 1997). Therefore, one of the most effective and expedient ways of reducing potential hazards posed to students in school and other buildings would be to conduct investigations of radon concentrations at as many school and home sites as is possible. Accordingly, student research conducted within the context of the Student Radon Research Project addresses scientific, educational, and enviornmental issues relevant to their communities.
REFERENCES
Ball, T. K., Cameron, D. G., Colman, T.B., and Roberts, P.D. 1991. Behavior of radon in the geological environment: a review. Quarterly Journal of Engineering Geology, Vol. 24: 169-182.
Environmental Protection Agency (EPA). 1993. "Radon - A Physician's Guide." EPA Document #402-K-93-008. Washington, DC: U.S. Environmental Protection Agency.
Environmental Protection Agency (EPA). 1994. "Radon In Schools." EPA Document #402-F-94-009. Washington, DC: U.S. Environmental Protection Agency.
Heiligmann, M., Stix, J., Williams-Jones, G., Lollar, B.S. and Garzon V. 1997. "Distal Degassing of Radon and Carbon Dioxide on Galeras Volcano, Colombia."Journal of Volcanology and Geothermal Research, Vol. 77, No. 1-4: 267-283.
Igarashi, G., Saeki, S., Takahata, N., Sumikawa, K., Tasaka, S., Sasaki, Y., Takahashi, M., and Sano, Y. 1995. "Ground-Water Radon Anomaly Before the Kobe Earthquake in Japan." Science, Vol. 269, No. 5520: 60-61.
King, C.Y. 1986. Gas geochemistry applied to earthquake prediction: An overview. Journal of Geophysical Research, Vol., 91, No. B12: 12,269-12,281.
Linpei, Cui. 1994. "Some Results of Radon Hazard Investigations." Geological Review, Vol. 40, No. 2: 157-164.
Neuberger, J.S. 1992. "Residential Radon Exposure and Lung Cancer: An Overview of Ongoing Studies." Health Physics, Vol.63, No.5: 503-509.
Samet, Jonathan M. et al. 1998. "Health Effects of Exposure to Radon: BEIR VI. Washington, DC: National Academy Press.
Schmidt, A, Puskin, J.S., Nelson, C, and Nelson, N. 1990. Estimate of annual radon-induced lung cancer deaths - EPA's approach. U. S. Environmental Protection Agency, The 1990 International Symposium on Radon and Radon Reduction Technology, Atlanta, Georgia.
Shirav M. and Vulkan, U. 1997. "Mapping Radon-Prone Areas; a Geophysical Approach." Environmental Geology, Vol. 31, No. 3-4: 167-173.
Siedel, J.L.1996. Personal Communication.
Stidley, C.A. and Samet, J.M. 1993. "A review of Ecologic Studies of Lung Cancer and Indoor Radon." Health Physics, Vol.65, No.3: 234-251.
Virk, H.S. and Singh, B. 1993. Radon Anomalies in soil-gas and groundwater as earthquake precursor phenomena. Tectonophysics, Vol. 27: 215-224.
RADON RELATED WEB SITES:
Applied Techniques Company -
http://www.atral.com/RnLinks.html
National Safety Council -
http://www.nsc.org/ehc/airqual.htm
Radon Information Center (this site contains a link to a clickable map that displays average radon levels by state) -
http://www.radon.com/radon/index.html
Radon Research Centre -
http://www.sbu.ac.uk/~rrc/index.html
United States Environmental Protection Agency -
http://www.epa.gov/iaq/radon/
United States Geological Survey -
http://sedwww.cr.usgs.gov:8080/radon/
http://sedwww.cr.usgs.gov:8080/radon/georadon.html
