to
Effects of ionizing radiation
Number +
tion Of vienicnis of the rachum and thorium
scri¢s, Of potassium-10 and of carbon-i+, pro-
my
tis san
IMMOwer
663
ve
r
GuPring
is tacking. In 1959, Brues®* commented that
the subject of effecis of low-level irradiation
concerned “hazards which, Hf they exist, cannot possibly be demonstrated to exist because
they are relatively so small.” Upton,?* in re-
i
a
ec
=
oO
“x
ry
oO
ue
oO
&
G2
leukemia for white children in wie United
we
Co
vi78 The radiauon exposure from radioisotopes in peciatric patients for a numberof
diagnostic tests has also been calculated.™
Adequate inrormation on effects of low
doses in both man and experimental animals
“might be of the order of 30 10 100 mrem.’
po
3
$2
y
oo
m4
a)
Is
vides radiation exposure frominternal sources
in dose rates estimaied to be 126 mrem1
year to the gonads, 130 mrem per vear to the
cells lining bone surfaces, and 122 m
year to the hematonoictic tissues.
Medical diagnostic radiology constitutes
another source of inevitavie low-level irradiation, the magnitude of which has been the
subject of recent inquiry.2% ° “ The annual
genetically significant dose received by an
individual in the Uniied States from diagnostic roentgenologic procedures has been
estimaica to be 356 = 25 mrem minimumand
140 + 100 mrem probabie.*® Alinough estimates ot bone marrow dose are bascc on
sparse data and assumptions, the UNSCEAK
in two reports has suggested that the catiimate oO: the populauon per capita cose
5ra
Ss
go
Ee
eo
a
i
wo
th
3
f,
o Bas
Volume 67
MacMahon* has reported the results
3 chilcren born in and discharged alive from 37 large maternity hosnitals in the northeastern part-of uc United
States from 1947 through 1954. For each of
three categories, ieukemia,“ys neoplasms of the
central nervous system, and other neoplasms,
he cancer rate was found to be “abour 40
percent Righer in the N-rayed than in the
unX-raved members of ihe stucy population. The excess cancer moriihy in the
N-cayed @rOuD WS MOst wiarkec at aves S
through 7 years, at which ume ie relative
risk was 2.0. The excess risk apparenUy was
exhaustea by age 8." MacMsiuon mus este
mated that the probablhy of death from:
-
Siates up to the age of 10 years wil be
increased from 46 per 100,000 chiidren to
62 per 160,000 children by prenatal irradiauion.**
In a prospective approach.* 43,742
women who between 1975 and i956 received pelvic irradiation qurh.. pregnancy
were Idenufed from the records of selec:
Viewing raciation carcinogenesis, stated that
hospitals (Edinburgh and London’ snc tne
subsequent deaths from leukemia of the chi
“onisting aia... are not ac equate tO Der-
dren of these pregnancies were then Invest-
mit conficent
1
estanation of the risks of small
increases in pacxground radiation.”
Sowane effects. The report by Srewar
anc asscciaces’” that dlagnostic pelvic irraGiatlon of tie pregnant mother was associatec
With subsequent development of leukemia
and others malignant neoplasms in the child
WAG Was exposed in uiero triggered a numye
ber Of shuilar epideniologic studies Ta subsequent communications, the original conclusions were confirmed and amplined?
The stucy attempred to trace all children
in England
and Wales who had died of
lecuxemia (792 cases) or other cancer (02
ases} before the tenth birthday during
1953-1955. It was concluded that the risk of
subsequent malignant changes in the chid
eaied. Court-Brown, Doll, and Hin.? in ihis
study, founc 9 instances o7 leukemia among
39,165 liveborn children when 10.3 was the
estimated expected number. The study abo
:
there was no evidence of any
proportionate
occurrence
of
leuxaemia
among the children who had been most
heavily irradiated nor among tne children
who had been irradiated early in intrauterine
wie.’ Data nor in accord with those of
Stewart and of MacMahon have woo been
reported from several other studies. 2?
Although the exposure dose cannot ve
preciscly determined in these suidies,' the
reporied association between prenata: pelvic
irradiation at diagnostic dose levels and intN
creased Icukemogenesis and carcinogenesis}