Transcript 13. Radon: A Deadly Carcinogen in the

13 Radon: A Deadly Carcinogen in the Geologic Environment
Joni Osborn, Western Oregon University
Faculty Advisor: Steve Taylor, PhD
Abstract
Radon: A Deadly Carcinogen in the
Geologic Environment
Radon is a naturally occurring noble
gas that results from radioactive
decay in uranium-bearing bedrock
and regolith. Radon occurs in a
variety of geologic settings around
the world, including the United
States.
Bedrock sources most
associated with radon include
metamorphic rocks and granites,
black shales, feldspathic glacial
deposits, and uranium ores. Health
hazards associated with this gas
include lung and stomach cancers,
caused primarily by inhalation or
ingestion.
Radon
exposure
increases chances of lung cancer
deaths in smokers and miners who
work in underground enclosures.
Radon hazard mapping helps
locate risk areas and guides public
health protection. Global hot spots
for radon exposure include the
Sierra Nevada-Rocky-Appalachian
mountain regions of the U.S. ,
glacial terrains of the upper
Midwest, Great Britain, Norway, and
the Czech Republic. This paper
provides an overview of the
geochemistry
behind
radon
occurrence and presents examples
of mitigation projects from around
the world.
Contact
Name: Joni Osborn
Organization: Western Oregon University
Dept. of Earth and Physical Sciences
Email: [email protected]
Introduction
Radon is a radioactive, naturally occurring
noble gas. A noble gas is odorless, colorless,
tasteless and has relatively low chemical
reactivity. Radon is the product of the decay of
radium. Radium is the product of the radioactive
decay of uranium (Appleton, 2007). Radon gas
is found throughout the United States and the
world. Radon gas disperses in the open air but
accumulates in enclosed areas. It is in these
enclosed areas where increased levels of radon
become a health hazard. There are ways to
mitigate radon gas in homes and buildings.
Extensive amount of epidemiological data has
accumulated over several decades relating to
studies of the incidence of lung cancer in
miners.
These
studies
consistently
demonstrated an increase in lung cancer
incidence with exposure to radon decay
products (Appleton2005).
Figure 1. Orange counties moderate potential,
Yellow counties low potential of radon
Case Examples
According to the Environmental Protection
Agency (EPA), twenty-three out of thirty-six
Oregon counties have the potential for
moderate levels of radon with the other sixteen
counties have the potential of low levels of
radon (EPA 2010). Polk County falls into the
potential of low level. Figure 1.
According to Appleton (2005) Studies of
thousands of miners, some with follow-up
periods more than thirty years, have been
conducted in uranium, iron, tin, and fluorspar
mines in Australia, Canada, China, Europe and
the United States. The results consistently
demonstrated an increase in lung cancer
incidence with exposure to radon decay
products.
The miner studies prove low
exposures over longer periods produced greater
lung cancer risk than high exposures over short
periods (Appleton, 2005).
Geologic Process/Phenomena
The radioactivity decay of Uranium produces the radioactive
decay of radium which radon gas is the result. Radon gas
(222Rn) is one of three radon isotopes 219Rn, 220Rn, and
222Rn. Uranium is found in granite, uranium-enriched, and
phosphatic rocks, uraniferous metamorphic rock. Granites in
southwestern England, the Czech Republic, and Germany
have high radon levels. The United States has a variety of
land formations that produce high levels of radon. Some of
these are uraniferous metamorphic rocks in the Rocky and
Appalachian Mountains and the Sierra Nevada. Marine black
shales from Ohio to Colorado contain high amounts of radon
(Appleton, 2005). Figure 2.
Radon enters buildings and
homes by 3 pathways. Figure 3.
Radon gas migrates up from the
ground underneath the basements
of foundations following minute
pathways.
Cracks
in
the
foundations, floors, walls and
areas below grade, gaps around
service pipes entering the house,
are all potential entrances for
radon gas. Houses in the United
States with basements have a
greater incident of higher radon
levels (Appleton 2005). Household
water sources that come from
enclosed groundwater have the
potential of having higher levels of
radon because there is not a way
to allow the degassing of the
water. Aeration of radon laden
water while running the shower or
faucets allows the radon gas to
enter the air in the building.
Building products that have been
made with radioactive shale add
to high radon concentrations.
Health Connection
Radon is the number one cause of lung cancer
among non-smokers, according to EPA estimates.
Radon is responsible for about 21,000 lung cancer
deaths every year (EPA 2010). Figure 4. Radon
causes 11% of lung cancer deaths among
smokers (most of whom die of smoking) but 23%
of never-smokers (Appleton, 2005). The U.S. EPA
estimates that radon in drinking water causes
about 168 cancer deaths per year, 89% from lung
cancer caused by breathing radon released from
water, and 11% from stomach cancer caused by
drinking radon-containing water (Appleton, 2005).
Figure 4. A cancerous lung
Summary
Figure 3. Keller, 2011
Environmental Geology
Prentice Hall 511
Radon mapping helps to determine if radon
protective measures may be needed in new
buildings, cost-effectiveness of radon monitoring
of existing buildings, and to provide a radon
assessment for home buyers and sellers
(Appleton, 2007). Since radon can seep into
homes through cracks in the foundations, service
pipe entrances, or any opening no matter what
size, eliminating the radon is essential. This
means keeping the radon out, remove what is
inside or dilute it with fresh air. To keep radon out
seal all openings and cracks. Use a low ventilation
fan that pumps air from the basement to above the
roof line. Diluting the radon gas with fresh air is
best for unused basements because it is not
economical because of increased heating or
cooling costs (The Natural Handyman, 2009)
References
Appleton, J. D., 2007, Radon: Sources, Health Risks, and Hazard Mapping:
Royal Swedish Academy of Sciences, 85-88.
Appleton, J. Donald, 2005, Essentials of Medical Geology: British
Geological Survey, 227-262
Environmental Protection Agency, EPA Map of Radon Zones,
URL:http://www.epa.gov/radon/zonemap.html
The Natural Handyman, 2009, Radon in the Home...How Dangerous is
it...Really?
Internet
Web
Resource,
URL:
http://www.naturalhandyman.com/iip/infsisters/infradon/infradon.html
Figure 2. Potential Radon map