RSH
Data & Documents
"Health Effects of
Low-level Radiation"
by Dr. Sohei Kondo
Table of Contents
Title Page: Front matter
Table of Contents
Terminology of radiation dose
|
2.3 Health effects of the fear of radiation
accidents
After the accident at the Chernobyl nuclear reactor, many people in Byelorussia and the
Ukraine reported that they were suffering from a variety of diseases; but many of those
diseases may be the result, at least partly, of the fear of radiation. The news that
radioactivity had been detected in soil, vegetables, meat and dairy products must have
shocked the local inhabitants. They may have suffered from the illusion that the Earth was
cursed by the devil radiation and that their food had been poisoned by that devil. Once
obsessed with this illusion, they would have become habitual worriers, and the
accumulation of stress would naturally have adverse effects on their health.
About 30 years ago, because of a shutter defect in an x-ray generator, I was accidentally
exposed to a much higher dose of radiation than the estimated life-time doses received by
residents of the 'hot' zones of the areas contaminated by radioactive nuclides in the
fall-out from the Chernobyl accident. I was admitted to a hospital affiliated with the
Tokyo University School of Medicine for about one week; but, since then, I have never
worried about the effect that my exposure to radiation may have had on my health. Now, I
am well acquainted with the various effects of radiation on humans, from the molecular to
the whole-body level. This book partly describes those effects.
2.3.1 Public panic about the radioactive fall-out from
Chernobyl, and press reports
Immediately after the Chernobyl accident on 26 April 1986, pregnant women living in
Kiev, close to Chernobyl, began to panic. They were terrified that their exposure to
'lethal' radioactive fall-out from the reactor accident would cause malformations in their
fetuses. Some of these women managed to persuade Hungarian students at Kiev University to
marry them temporarily or they married previously so that they could go to Budapest to
undergo medical examinations. High levels of radioactivity were detected around the
thyroid glands of these women because of intake of radioiodine released in the accident.
This exposure was called 'lethal fall-out' and given top coverage in the media.
Dr Andrew Czeizel, Department of Human Genetics and Teratology, National Institute of
Public Health in Budapest, one of the most respected medical geneticists in the world,
told the women that the amounts of radioiodine detected would scarcely harm their fetuses.
His opinion was based on radiological knowledge of the threshold for induction of
malformations in fetuses after irradiation (see Section 3.3)
and of the fact that high levels of radioactivity are localized in the thyroid gland
because of the selective uptake of radioiodine by the thyroid gland; fetuses would receive
much lower levels of radioactivity. Most of the patients, however, appear to have
disregarded Dr Czeizel's advice and wanted to undergo therapeutic abortions. However, the
Abortion Committee in Hungary did not allow it in the majority of the cases.
Dr Czeizel thought of telling the press that the doses of radiation received from
radioiodine and other nuclides released in the Chernobyl accident were too low to induce
malformations in fetuses and that therapeutic abortions were thus unnecessary. He did not
disseminate this important information, however, because he feared that it would be
misunderstood by readers and that they would probably interpret his report to mean the
contrary. In fact, many Hungarians did panic shortly after the Chernobyl
accident--unnecessarily, as is shown below.
As a consequence of the Contergan thalidomide catastrophe, a nation-wide registry of
congenital malformations was established in Hungary in 1963. This system is one of the
most reliable networks in the world. It provides monthly reports on a wide range of
pregnancy outcomes, including induced abortions, fetal deaths, births of babies weighing
less than 2500 g, isolated congenital anomalies, identified multiple congenital anomaly
syndromes that include radiation syndromes, isolated congenital anomalies, and
unidentified multiple congenital anomalies (Czeizel, 1991).
Of these categories, only the number of newborns weighing less than 2500 g showed a
significant increase in monthly incidence, rising from the normal level of under 10% to
10.7% in May and June 1986, the first two months after the accident (Table 2.5; Czeizel and Billege, 1988).
Since the excess dose of radiation accumulated during those two months was less than 0.05
rad (Feher, 1988), the observed increase in preterm
births must have been due to some factor other than radiation (Czeizel, 1990). Czeizel and Billege (1988) proposed that
the increase was the result of preterm labor caused by psychological anxiety.
Psychological stress is known to cause preterm labor and consequently the birth of
abnormally small babies (Newton et al., 1979).
Table 2.5 Monthly distribution of pregnancy outcomes in Hungary from
1986 to the first quarter of 1987 (from Czeizel
and Billege, 1988)
Year Induced Spontaneous Still- Live Live birth Congenital
Month abortion abortion birth birth <2500 g abnormality
---------- ----------- ------- ----- ---------- ----------
nd % nd % nd % nd nd % nd %
--------------------------------------------------------------------------
1986
Jan 248.8 38.1 53.0 13.1 2.6 0.7 349.8 34.1 9.7 13.6 3.85
Feb 261.8 39.1 50.9 12.5 2.4 0.7 355.1 32.8 9.2 13.6 3.80
Mar 216.7 34.6 50.7 12.3 2.3 0.6 357.5 36.0 10.1 12.5 3.46
Apr 246.6 37.6 49.5 12.1 2.8 0.8 356.6 35.8 10.0 10.3 2.86
May 225.1 36.4 50.6 12.9 2.6 0.8 340.2 36.3 10.7* 12.5 3.63
Jun 224.1 35.3 45.7 11.1 1.9 0.5 363.4 39.0 10.7* 11.5 3.14
Jul 236.1 35.2 53.4 12.3 2.3 0.6 379.8 37.3 9.8 11.3 2.95
Aug 199.3 32.5 47.5 11.5 2.4 0.7 364.1 35.9 9.9 10.6 2.90
Sep 239.8 36.9 49.5 12.1 2.3 0.6 358.4 32.7 9.1 11.0 3.05
Oct 211.1 35.3 50.4 13.1 1.8 0.5 333.6 29.5 8.8 10.1 3.00
Nov 201.3 35.1 47.5 12.8 1.9 0.6 322.9 30.9 9.6 10.1 3.11
Dec 227.3 37.0 51.1 13.2 2.0 0.6 333.8 34.1 10.2 9.4 2.80
1987
Jan 243.5 38.4 47.6 12.2 2.3 0.6 340.8 33.5 9.8 - -
Feb 251.1 39.1 49.6 12.7 2.2 0.6 338.9 33.0 9.7 - -
Mar 226.1 35.2 48.8 12.5 2.2 0.6 344.9 33.0 9.6 - -
nd = daily mean number
* p <0.01
In
order to estimate the possible number of victims in Greece of fear of the radioactive
fall-out from the Chernobyl reactor accident, Trichopoulos et al. (1987) surveyed temporal
changes in the monthly numbers of live births before and after the accident. The observed
and (in parentheses) expected figures for January, February and March 1987 were: 7032
(9103), 7255 (7645) and 8350 (8453), respectively, whereas in December 1986 there had been
no reduction in the number of live births in comparison with the numbers in 1981 85 (Fig.
2.6). These results were interpreted as showing that, during the period of concern after
the Chernobyl accident, i.e., May 1986, 23% ([9103 7032]/9103) of early pregnancies at
perceived risk were artificially terminated and that, for the whole of 1986, about 2500
otherwise desired pregnancies were interrupted because of fear of radiation.
Fig. 2.6 Observed (open circle) and expected numbers of live births in Greece
during January 1987
Expected numbers were calculated on the basis of the 1981 86 linear
trend of the number of live births during January of the corresponding year (filled
circles) and the average monthly number of live births throughout the corresponding year
(filled squares) (from Trichopoulos et al., 1987.
Copyright British Medical Association, London. Reproduced with permission)
In Hungary, termination of pregnancy due to the Chernobyl fallout was not allowed, despite
large proportion of legal abortions (Table 2.5), owing to the Abortion Law as the
'Abortion' Committee judged that excess doses by radioactive fallout from the Chernobyl
accident were far below the lowest intervention dose of 10 rad to fetuses in the first 12
weeks (Czeizel, 1991). In fact, monthly distribution of
induced abortions in the period of May of 1986 to April of 1987 did not significantly
differ from that averaged over the period 1980-1989 excluding 1986 (Czeizel, 1991; see Table 2.6A for the cases of May and
June of 1986). It is, however, noteworthy that monthly distribution of live births (% of
the total live births per year) in February and March of 1987 was significantly lower than
that averaged over the period 1980-1989 excluding 1987.
From the data of Czeizel (1991), we estimate that
the decrements in the number of monthly live births in February and March of 1987 as
compared with the corresponding number of monthly live births averaged over other years
sum up to about 800 live births. This estimate is compatible with the annual excess of the
decrement in the number of live births, [- deltaNl], in 1987 over [- deltaNl]
in 1986 or 1988, as seen in Table
Table 2.6 Pregnancy outcomes in Hungary, 1980-89
A. Monthly distribution of induced abortions and live births in the indicated month
compared with that (with 95% confidence intervals) averaged over 1980-1989
Month Induced abortions (% of total/year) Month Live births (% of live births/year)
----------------------------------- -----------------------------------
1986 1980-89 (except 1986) 1987 1980-89 (except 1987)
--------------------------------------------------------------------------------------
May 8.44 8.40+/-0.35 Feb 8.20 8.56+/-0.28
Jun 8.03 8.33+/-0.35 Jun 8.21 8.50+/-0.26
B. Distribution of pregnancy outcomes, 1985-1989
Year Live births/year Difference All pregnancy outcome Difference
---------- per year minus Nl ----------------
(Nl) (delta Nl) (Nt - Nl) delta(Nt - Nl)
-------------------------------------------------------------------------------
1985 130,200 100,848
1986 128,204 -1,996 102,708 1860
1987 125,840 -2,364 103,131 423
1988 124,296 -1,544 105,917 2786
1989 123,304 - 992 106,602 685
Constructed from the data of Czeizel, 1991
Czeizel (1991) interpreted these results as
indicating that people were so frightened of 'lethal' radioactive fall-out from Chernobyl
during the following two months that many of them practiced intensive birth control during
that period, resulting in the decrease in live births 9 months later.
In many countries in western Europe, legal abortions increased for several months
following the Chernobyl accident probably because of fear of the effects of the
radioactive fall-out (see, e.g., Fig. 2.6); according to the IAEA, 100,000 to 200,000
excess abortions were performed throughout western Europe after the Chernobyl accident (Ketchum, 1987).
2.3.2 Soviet citizens stubbornly continuing to live in
highly contaminated areas and survivors of the atomic bombing in Nagasaki: people
resisting despair
In 1990, a large number of people were evacuated to radioactivity-free areas from their
homes in Byelorussia, the Ukraine and Russia, where the levels of radioactivity from
radioactive fall-out were so high that the estimated life-time dose would be over 35 rem (Int. Adv. Comm. IAEA, 1991).
Gomel' is one of these heavily contaminated areas (see Fig. 2.3). Recently, Professor Y.
Satow, of the Hiroshima University School of Medicine, visited Gomel' (see Fig. 2.3); he
subsequently made the following comments to a Japanese newspaper. "I was very
shocked to find that there were still many people living in dangerous zones with high
radiation levels in spite of the governmental order to evacuate their homes and farms,
although I sympathize with the farmers who love their farm lands so much that they want to
remain on them. I understand their bitter feeling of possible loss and their fears of
future uncertainty in new places. Nevertheless, I feel that evacuation from their homes
and farm lands is the best way to prevent illness in the future due to the high levels of
radioactivity." This opinion is probably shared by the majority of radiation
protection experts, since the evacuation criterion of 35 rem established by the NCRP of
the USSR was supported by radiation experts from the international organizations for
radiation protection--the IAEA, the World Health Organization and the United Nations
Scientific Committee on the Effects of Atomic Radiation (Gonzalez,
1990).
As a scientist who majored first in radiation physics and later in radiobiology in a
medical school, I support the intuitive decision of residents to stay in their homes in
spite of the considerable contamination of their homes and land with radioactive fall-out.
Furthermore, I would not be surprised if those who stayed in houses contaminated by
radioactive fall-out lived longer than those who moved away. There are many lines of
evidence for me to believe so. The first is described below and the others in the
following chapters.
The first line of evidence is based on the results of an epidemiological study of deaths
among survivors of the atomic bomb in Nagasaki, published by Mine et al. (1981)
after surveying 7,782 deaths occurring in 1970-76. As indicated in Figure 2.7, the
age-specific mortality rates among the bomb survivors over the age of 60 were
significantly lower than among control citizens.
Fig. 2.7 Comparison of age-dependent rates of mortality (1970-76) for atomic
bomb survivors (solid line) and controls (broken line) in Nagasaki
Mortality rates are averages for 1970-76 at five-year intervals; e.g.,
the rate at age 30 is the average for ages 30-34 years (constructed from data of Mine et al., 1981)
In the comparison of Mine et al., atomic bomb survivors are defined as people who
were given an 'Atomic Bomb Survivor Health Handbook' (hibakusha techo
in Japanese) by the Japanese Government via the Nagasaki City Office after they had been
confirmed as authentic atomic survivors, whereas unexposed groups are defined as people
living in Nagasaki City but without a health handbook. The health handbook holders receive
free medical care and subsidies for diseases for which a possible causal relation with the
atomic bombing is presumed, and, when they die, funeral subsidies are given to their
relatives by the Ministry of Health and Welfare of Japan. According to a survey, health
handbook holders undergo more frequent health examinations than people who do not have the
handbook. Slight changes in the life style of atomic bomb survivors, who are more
concerned with their health than other people, may also have a favorable effect on their
longevity, despite the exposure to radiation.
Experts in epidemiology and other branches of life sciences criticized the study of Mine et al. (1981) and argued that the atomic bomb
survivors must have suffered from worry and anxiety during the long period since they were
exposed to the bomb; most of them may have had to live more stoically, in fear of
potential diseases, than unexposed citizens. Therefore, it is possible that changes in
life style, rather than radiation, reduced the mortality of atomic bomb survivors compared
with unexposed citizens. I, too, would regard this paper as of little value if I were
still in the ivory tower of the National Osaka University School of Medicine, because the
comparison of the two groups described in the paper lacks scientific rigidity. Now,
however, I greatly appreciate the value of this paper because of its view of the real
world. The real data on survivors of the atomic bomb in Nagasaki might be very valuable to
those residents of the ex-USSR who have decided to continue living in their highly
contaminated homes, opposing the governmental order to evacuate them.
Human beings cannot be studied like experimental animals, and data on humans are almost
always considered to be incomplete from the academic point of view. The available factual
data on humans exposed to low-level radiation are, however, invaluable, and I propose now
that we exercise rationality in handling these incomplete but important data. This change
in my view of the evaluation of scientific data has come about gradually, since April
1986, when I retired from the National Osaka University and took a research job at Kinki
University, a private establishment. This was also at the time of the Chernobyl accident.
I was thus forced to face public opinion, because I met more people in private enterprises
than I did Government officials.
I considered that it might be worthwhile to test the possibility that the atomic bomb
survivors overcame the harmful effects of radiation and lived longer than unexposed
people, not because of a 'healthy survivor effect', but because of a beneficial effect of
low-dose radiation. To exclude the 'healthy survivor effect', mortality rates were
compared between two subgroups of health handbook holders: an exposed group made up of
people exposed to more than 1 rad and an 'unexposed' group made of people exposed to less
than 0.5 rad. As can be seen from the preliminary data given in Table 2.7, the mortality
rates of people exposed to more than 1 rad of radiation are lower than those of the people
exposed to less than 0.5 rad. This finding was true for both men and women, except for
women aged over 80 and men aged 30 39 years. The data I show here can be readily
understood by ordinary people. I shall not bother my readers with the statistical
analysis, which will be published elsewhere.
Table 2.7 Annual mortality rates (per 100,000), 1970-76, in
Nagasaki
Sex Age Bomb survivorsa Controlsb
-----------------
(years) >1 rad <0.5 rad
Male
30-39 205 201 188
40-49 375 489 417
50-59 1,036 1,201 957
60-69 2,119 2,485 2,640
70-79 6,342 6,856 8,856
80 15,758 16,319 32,673
Female
30-39 78 87 103
40-49 218 224 223
50-59 428 569 510
60-69 833 1,303 1,516
70-79 3,242 4,161 5,305
80 13,158 12,626 19,634
Personal communication from M. Mine and Y. Okumura
a Holders of the Atomic Bomb Survivor Health Handbook (see text)
b Citizens without the health handbook
However, cautious readers may raise the possibility that the decrease in mortality in
every age group above 30 is simply because the less healthy 10-20% of the exposed
population have already died as the result of the bomb explosion. This possibility is
discussed in the next chapter, using data on mortality in 1950-1985 among bomb survivors
in Hiroshima as well as Nagasaki.
References
To:
|
|
