Health Hazards Associated with Elevated Levels of Indoor Radon --
Pennsylvania
As a part of the safety program at the Limerick Nuclear Power
Plant in Pennsylvania, personnel entering the plant must pass
through
a radiation monitoring area. In December 1984, the monitoring
device
detected an abnormally high level of radiation in one construction
worker. When an investigation was made to determine how and where
this worker was being exposed to excessive radiation, investigators
found that the air in the man's home contained extremely high
levels
of "radon daughters," the short-lived decay products of radon-222.
Radon is an inert, radioactive gas formed in the decay chain of
uranium-238. For each year the worker and his family lived in this
house, they were exposed to over 50 times the annual occupational
limit of exposure for uranium miners. The family relocated until
remedial actions to lower the indoor radon levels could be
completed.
As a result of this incident, in January 1985 state officials
in
Pennsylvania began a sampling program in which over 2,000 homes
around
the construction worker's house were examined. The homes are in an
area of natural uranium deposits. Approximately 40% of the homes
had
radon levels exceeding the U.S. Environmental Protection Agency
(EPA)
guideline for indoor radon of 0.02 "working levels." A working
level
is a measure of radon daughter concentrations and is defined as any
combination of radon daughters in 1 liter of air that results in
1.3 x
10((5)) million electron volts of potential alpha energy. About 7%
of
the homes tested had radon levels at or above the 0.1 working
level.
If residents in these homes spend 75% of their time indoors exposed
to
0.1 working level, their yearly exposure would equal 4 working
level
months, the annual occupational limit of exposure. A working level
month is a measure of exposure and is a function of the time of
exposure and the level of radon daughters, given in working levels.
Reported by J Logue, DrPH, J Fox, MD, Pennsylvania Dept of Health;
Cancer Br, Div of Chronic Disease Control, Center for Environmental
Health, CDC.
Editorial Note
Editorial Note: The elevated radon levels near the eastern border
of
Pennsylvania are associated with natural uranium deposits that
extend
into northern New Jersey and southern New York. Since similar
geologic deposits are found throughout the country, the elevated
radon
levels in Pennsylvania may indicate a much broader national
problem.
Radon enters a building through cracks, such as those in a basement
floor, and through openings around pipes and wiring. Once inside,
the
radon builds up in the air, particularly in poorly ventilated
houses.
As radon daughters are formed, they attach to airborne
particulates.
When inhaled, these particulates can deliver a substantial dose of
radiation to the bronchial epithelium.
No exposure limit has been established for indoor levels of
radon
from natural sources; however, EPA is now developing guidelines
that
will define action levels concerning houses with high
concentrations
of radon and is developing and evaluating mitigation strategies.
Exposure to radon daughters increases a person's lifetime risk
of
lung cancer. The risk rises in direct relationship with the length
of
exposure and with radon daughter levels.
The two risk estimates in Table 1 are derived from studies of
uranium miners and have been extrapolated from relatively high
occupational exposures to environmental levels. The highest
lifetime
risk calculated from studies of uranium miners is 7.3 x 10))-4))
deaths per working level month, and the lowest generally accepted
risk
is 3.0 x 10))-4)) deaths per working level month (1,2). These
estimates are for the general population, including smokers. The
risks for nonsmokers are approximately six times less than those
given
in the upper portion of the table (1).
Each year, approximately 5,000-30,000 deaths may be attributed
to
background levels of indoor radon. The health threat from radon
can
be addressed by identifying geographic areas that could produce
elevated levels of indoor radon, developing strategies to reduce
exposure, conducting research on effective remedial measures to be
taken in buildings, and providing educational programs for health
officials and the public. Changes in usage patterns of high-radon
areas in a home, such as the basement, and the control of future
construction in geographic areas high in uranium deposits can
reduce
exposure. Effective remedial measures for individual dwellings can
also be used to lower radon exposure. Research in these areas
should
be coordinated with other agencies active in this field. The
educational programs can be used to inform health officials and the
public about the health threat from radon and about associated risk
factors, such as smoking.
References
National Research Council. The effects on populations of
exposure
to low levels of ionizing radiation. Washington, D.C.:
National
Academy Press, 1980.
International Commission on Radiological Protection. Limits
for
intakes of radionuclides by workers. ICRP report no. 32, part
3,
1981.
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