Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

BIOLOGICAL BASIS FOR R ADIATION SAFETY 325
TABLE 7-11. Lung Cancer Among Miners Occupationally Exposed to Radon and
Radon Daughters
DATES OF PERSON-YRS MEAN LUNG CANCER ERR %
STUDY FOLLOW-UP AT RISK WLM DEATHS PER WLM a
China 1976–1987 134,842 286.0 936 0.16 (0.1–0.2)
Czech Republic 1952–1990 102,650 196.8 701 0.34 (0.2–0.6)
Colorado 1950–1990 79,556 578.6 334 0.42 (0.3–0.7)
Ontario 1955–1986 300,608 31.0 285 0.89 (0.5–1.5)
Newfoundland 1950–1984 33,795 388.4 112 0.76 (0.4–1.3)
Sweden 1951–1991 32,452 80.6 79 0.95 (0.1–4.1)
New Mexico 1943–1985 46,800 10.9 68 1.72 (0.6–6.7)
Beaverlodge, Canada 1950–1980 67,080 21.2 56 2.21 (0.9–5.6)
Port Radium, Canada 1950–1980 30,454 243.0 39 0.19 (0.1–0.6)
Radium Hill, Australia 1948–1987 24,138 7.6 31 5.06 (1.0–12.2)
France 1948–1986 29,172 59.4 45 0.36 (0.0–1.2)
a Numbers in parentheses are 95% confidence intervals. Estimates are adjusted for age (all studies), other mine exposures (China,
Colorado, Ontario, New Mexico, and France), an indicator of Rn exposure (Beaverlodge), and ethnicity (New Mexico).
Abbreviations: WLM, working level month; ERR, excess relative risk.
Reprinted with permission from the National Academies Press from BEIR VI: Health Effects of Exposure to Radon. Washington, DC:
National Academies Press; 1999. Copyright c○ 1999, National Academy of Sciences.
of radon and its progeny. One WL is defined as any combination of short-lived radon
daughters in 1Lofairthat will result in the ultimate emission of 1.3 ×10 5 MeV of alpha
energy. This corresponds to an atmospheric concentration of 100 pCi of 222 Rn per
liter (3700 Bq/m 3 ) in equilibrium with its daughters. One WLM is the exposure
resulting from inhalation of air with a 1-WL concentration for a period of 1 working
month (170 hours). An exposure of 1 WLM under conditions in a mine results in
an alpha dose to the lung of about 1200 mrads (12 mGy) to the critical target cells
in the lung.
When estimating the lung-cancer risk from inhaled radon daughters based on
data on uranium miners, it should be understood that the uranium miners had
been exposed to other noxious agents and potential carcinogens, such as diesel
engine exhaust and inhaled mine dust that contained uranium and other minerals,
including silica. These other agents, which may have contributed to the increased
lung-cancer incidence found among the uranium miners, were accounted for in
calculating the ERRs in Table 7-11.
Airborne radioactivity may be inhaled either as gaseous matter, soluble particles,
or relatively insoluble particles. Inhaled gas is assumed to be uniformly distributed
throughout the lung. The deposition of particles within the lung depends mainly
on the particle size of the dust, while the retention in the lung depends on the
physical and chemical properties of the dust as well as on the physiological status of
the lung. The radionuclide in an inhaled soluble particle may, after dissolving in the
lung, be absorbed into the body fluids and translocated to a tissue or organ where
it may be deposited. Depending on the chemical form of the inhaled radionuclide,
the radionuclide from the dissolved particle may also bind to the protein in the
lung. Relatively insoluble particles that are deposited in the upper respiratory tract
are rapidly cleared from the lung and swallowed. Those insoluble particles that are
deposited in the deep respiratory tract remain there for relatively long periods of
time and may subject the pulmonary tissue to a severe local radiation insult due to