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

RADIATION SAFETY GUIDES 421
Substituting this value into Eq. (8.68) and solving for the dose rate gives
˙D =
f DAC
0.114
0.33
= = 2.9 mrems/h.
0.114
Since the dose rate in this example exceeds 2.9 mrems/h, wearing a respirator would
decrease the worker’s efficiency, thereby increasing his or her total exposure time
and leading to a greater TEDE than if he or she had not worn a respirator. In this
case, the worker would have received a TEDE of 12.7 mrems with a respirator but
only 11.7 mrems without a respirator.
ECOLOGICAL RADIATION SAFETY
SUMMARY
Radioecology and environmental health physics evolved mainly in the context of
risk assessment to humans, and thus may be considered anthropocentric. To this
end, radiation-exposure pathways and potential exposure to humans from naturally
occurring radioisotopes and from residual anthropogenic environmental radioactivity
was extensively studied. A long-term (25 years) study of the environmental and
human-health effects from a nuclear power plant that discharged liquid radioactive
waste into a major river within the guidelines of the U.S. NRC found that the releases
had no known environmental or human-health impact. It was believed that
the environmental radiation safety standards that had been developed would also
be protective of the biosphere. This belief seems reasonable, since all life evolved in
a higher radiation environment than the present one. Now there is an increasing
societal concern about the health of the environment. However, there is no universally
accepted agreement about what we mean by the “environment.” In the case of
nonhuman species, for example, are we interested in protecting individual members
of the species, as in the case of humans, or is our interest in protecting the
species in the interests of biodiversity? To answer some of these questions, the ICRP
has suggested that a framework be developed for assessing the impact of ionizing
radiation on nonhuman species.
The harmful effects of overexposure to ionizing radiation were seen almost immediately
after the discovery of X-rays and its introduction into medicine, science,
and industry. Initially, the incidence rate of cancer and other harmful effects among
users of radiation was relatively high. For example, during the period 1929–1949, the
death rate of radiologists from leukemia was nine times greater than the leukemia
death rate among nonradiologist physicians. Today, the leukemia rate among radiologists
is no greater than among their nonradiologist colleagues. Furthermore, the
nuclear industry today is among the safest of all industrial enterprises. Eight different
epidemiological studies of 15,674 deaths among 77,000 nuclear workers found
the overall standardized mortality ratio (SMR) for all causes of death to be 82 and
the SMR for cancer deaths to be 90. (An SMR of 100 means that the actual number