Environmental Engineering Reference
In-Depth Information
metric mean value of 1.74 pCi/L. Five percent of the values were less than
0.2 pCi/L; 0.5% exceeded 100 pCi/L. The Northeast, Midwest, and Mountain
States reported the highest geometric mean concentrations and potential
exposures; the Northwest and Southeast the lowest. These data were based
on purchased test kits and are not randomly representative of the U.S.
housing stock. High regional geometric mean concentrations reflect, in part,
both high regional interest in radon testing and localized areas of high radon
concentrations. A geometric mean concentration of 0.9 pCi/L has been
reported in a more random study of single-family dwellings from 32 areas
of the U.S. (primarily urban areas).
Radon concentrations vary considerably from region to region and house
to house. Houses located next to each other may have radon concentrations
that differ by an order of magnitude or more. These differences reflect radon
emission potentials under each structure as well as differences in radon
transport into them.
E.
Health effects
The major health concern associated with exposure to radon and its RDPs
is their potential to cause cancer. Epidemiological studies of uranium and
other deep miners have shown a very strong correlation between RDP expo-
sure and lung cancer. Lung cancer risk is dependent on the total, or cumu-
lative, dose (
Figure 2.10
)
.
The upper bronchial region of the lung is the primary tissue site exposed
to
-particle emitters produced in radon decay. Other potential cancer sites
include the buccal cavity (back of the mouth), pharynx (throat), upper por-
tions of the gastrointestinal tract, and bone. There is also limited epidemio-
logical evidence to suggest that radon exposure may be an important risk
factor for acute myeloid leukemia, cancer of the kidney, melanoma, and
certain childhood cancers.
α
Figure 2.10
Cumulative radon RDP exposures and lung cancer rates. (From Na-
tional Research Council,
Health Risks of Radon and Other Internally Deposited Alpha
Emitters, BIER IV
, National Academy of Science Press, Washington, D.C., 1988. With
permission.)
