cancers, nonfatal cancers, and hereditary effects have been estimated by the
ICRP to be 4.0%, 0.8%, and 0.8%, respectively, for adult radiation workers
and 5.0%, 1.0%, and 1.3%, respectively, for the whole population (ICRP
60, 1991).
An important quantity in the assessment of risk from radiation exposures
is the collective effective dose, which is defined as the sum of the products
of the effective dose and the number of persons exposed for each diagnos-
tic procedure (NCRP 100, 1989). The age-weighted value per year for low
dose and dose rates is estimated to be 58,000 person-Sv (5.8 million person-
rems) for diagnostic radiological procedures and 13,500 person-Sv (1.35
million person-rems) for nuclear medicine procedures in the United States.
Based on a collective effective dose of 58,000 person-Sv (5.8 million
person-rems) and the probabilities of cancers given above, Hall (1994) esti-
mated the risks from 1 year of diagnostic radiology practice to be 2320 fatal
cancers, 464 nonfatal cancers, and 464 serious heritable defects. Similarly,
based on a collective dose of 13,500 person-Sv (1.35 million person-rems),
the risk from 1 year of nuclear medicine practice is 540 fatal cancers, 103
nonfatal cancers, and 108 serious heritable defects. These risks are quite low
compared to the number of examinations performed annually.
The benefit from diagnostic procedures (both x-ray and nuclear medi-
cine) is the immediate diagnosis of the disease that can lead to the appro-
priate treatment and its ultimate cure. Argument should prevail in favor of
the benefit for the use of radiation for diagnosis over the risks that may
appear in later years in the individual himself or the future offspring.
However, a judicious use of these procedures is definitely warranted, and a
procedure that is not needed should not be done. This argument for the
prudent use of radiation also applies to different screening procedures using
x-ray, such as mammography, chest x-rays, and dental x-rays. Many individ-
uals are exposed for screening, but only a small number of people benefit
from the early diagnosis, while most of the screened people turn out to be
negative. For this reason, the American College of Radiology has recom-
mended annual mammography only for women above 40 years of age,
excluding younger women who are much more radiosensitive, some of
whom may likely develop breast cancer many years after mammography.
Risk to Pregnant Women
Since radiation can cause a devastating effect on the embryo and fetus in
pregnant women, diagnostic radiological and nuclear medicine procedures
are contraindicated in pregnant women, despite only a small risk involved
with the individual exposed from these procedures. This is particularly
important in nuclear medicine procedures, because radiopharmaceuticals
reside in the body following a biological half-life and are likely to cross the
placenta to cause the fetal damage.b-emitting radionuclides are more
Risk to Pregnant Women 259