Danger to the Individual
How much harm is being done by the atomic tests? Some scientists have
claimed that from past tests alone about 50,000 persons throughout the
world will die prematurely. There is no general agreement on this point.
Some think the number should be smaller. It is possible that
radioactivity produces some effects which prolong life rather than
shorten it. But even if all the biological consequences of radiation
were known many questions would still demand answers. Can tests be
justified if they actually shorten some human lives? Even the
possibility of a health hazard must be taken most seriously. On the
other hand: Are there any reasons which make continued testing
necessary?
We shall return to these questions in a later chapter. First, however,
we shall try to put before the reader the known facts about the fallout
danger to the individual. We shall try to put this danger into
perspective by relating it to other more familiar dangers to which all
of us are exposed. In the following chapter we shall discuss how the
fallout may affect future generations.
The dangers from big doses of radiation are well known. Exposure to a
thousand roentgens over our whole body causes almost certain death in
less than thirty days. Four or five hundred roentgens give a fifty-fifty
chance of survival. At less than a hundred roentgens, there is no danger
of immediate death. Three years ago the Marshallese got a dose of 175
roentgens. None died. Apparently all are in good health.
Over longer periods of time even bigger radiation doses can be
tolerated. A thousand roentgens spread over a lifetime produce no
apparent biological consequences in individual cases. A rough rule
(which is not too well-established) is that five times as much radiation
can be tolerated if one is exposed to only a little radiation at any one
time.
A hundred roentgens all at once, or several times this amount over a
protracted time period, will not cause sickness or death that can be
directly blamed on the radiation. However, such a dose of radiation may
have harmful biological consequences which are more subtle. An exposed
individual may develop an increased susceptibility to certain diseases,
notably bone cancer and leukemia. Leukemia is a fatal disease in which
the white blood cells multiply too rapidly.
A person who receives a hundred roentgens does not necessarily contract
bone cancer or leukemia. Rather, his chance of contracting these
diseases during his lifetime may have been increased. Knowledge of this
kind can be obtained only with the help of statistics.
If, for example, a large number of mice receive a heavy dosage of
radiation over a long period of time, one finds that the incidence of
tumors and leukemia is higher amongst such irradiated animals than the
natural incidence of these diseases.
Direct evidence with human beings—fortunately—is rather scarce.
Statistics exist on the survivors of Hiroshima and Nagasaki, and also on
radiologists. The latter group probably receive several hundred
roentgens during their professional lifetimes. In addition, some
statistics exist on children who have been treated with large doses of
radiation for enlarged thymuses. Persons suffering from ankylosing
spondylitis, which is a painful disease of the spinal joints, have also
been treated with large X-ray doses. The statistics in all these cases
lead to the same conclusion: that large doses of radiation increase the
likelihood that an individual’s life will be shortened by leukemia and
possibly also other cancers. Furthermore, it appears (mainly from the
experiments on animals) that the increased likelihood is simply
proportional to the amount of radiation received, at least for doses in
the neighborhood of several hundred roentgens or so.
This of course sounds frightening. But the radiation doses from the
world-wide fallout are in a completely different class from those we
have been discussing. They are very much smaller. On the average human
bones are getting about 0.002 roentgens per year from the Sr⁹⁰ in the
fallout. In addition the whole body is receiving a roughly equal amount
in gamma rays, mainly from Cs¹³⁷. These figures apply to new bone in
young children who have grown up in an environment of Sr⁹⁰ in the
northern part of the United States. This is a region of maximum fallout.
Adults whose bones were made for the most part before the atomic testing
started are getting about 0.0003 roentgens per year from Sr⁹⁰. None of
these figures appears to be alarming.
At this present rate a lifetime dosage in northern U.S. is only a small
fraction of a roentgen. A rare individual might get several times this
amount. If tests continue at the present rate, radiation levels could
increase by as much as five-fold. However, even in this situation it is
difficult to imagine anyone receiving a lifetime dose of more than five
or ten roentgens from the world-wide fallout. A more reasonable estimate
for the average lifetime dose would be a few roentgens or less.
One might conclude from these figures that there is no danger whatsoever
from the fallout. This conclusion, however, may not be correct.
The danger from such small doses of radiation is not easy to define.
Even the best statistical methods are insufficient. One is looking for
small effects which show up only after millions of cases have been
studied. Animal experiments are extremely difficult to carry out under
these conditions. Direct controlled experience with human beings is, of
course, impossible. As a result, one is forced to draw conclusions from
the effects at higher dose levels, where experimental data have been
obtained.
This may be done in many ways. One way is to assume that the law of
proportionality holds down to the smallest doses. This means that one
roentgen produces one hundredth as many cases of bone cancer and
leukemia as 100 roentgens produce. This law is plausible. It is by no
means proven.
By arguing in this way one finds that for each megaton of fission energy
which escapes from the test site in the world-wide fallout the lives of
approximately four hundred persons would be shortened by leukemia or
bone cancer. Under present conditions of testing, roughly one half of
the fission products are deposited as close-in fallout in and near the
test site. Per megaton of fission energy exploded, therefore, perhaps
200 persons may get leukemia or bone cancer. This figure could actually
be higher, possibly even a thousand persons or more per megaton. It
could also be lower. It could be zero.
It is possible that radiation of less than a certain intensity does not
cause bone cancer or leukemia at all. In the past small doses of
radiation have often been regarded as beneficial. This was not supported
by any scientific evidence. Today many well-informed people believe that
radiation is harmful even in the smallest amounts. This statement has
been repeated in an authoritative manner. Actually there can be little
doubt that radiation hurts the individual cell. But a living being is a
most complex thing. Damage to a small fraction of the cells might be
beneficial to the whole organism. Some experiments on mice seem to show
that exposure to a little radiation increases the life expectancy of the
animals. Scientific truth is firm—when it is complete. The evidence of
what a little radiation will do to a complex animal like a human being
is in an early and uncertain state.
In any event the number of additional cases of leukemia and bone cancer
due to the fallout radiation is certainly too small to be noticed
against the natural incidence of these disorders.
In the next thirty years about 6,000,000 people throughout the world
will die from leukemia and bone cancer. From past tests, which have
involved the explosion of about fifty megatons of fission energy, the
possibility exists that another 50 × 200, i.e., 10,000 cases may occur.
Statistical methods are not able to find the difference between
6,000,000 and 6,010,000. There is no way to differentiate between the
fallout-induced cases of leukemia and bone cancer, and those which occur
naturally.
The possible shortening of ten thousand lives may seem rather ominous.
But mere figures can be misleading. A better way to appreciate the
danger from fallout is to compare it with other more familiar dangers.
Such a comparison can be made with the natural background of cosmic rays
and radioactivity in the earth and in our own bodies.
We are constantly and inescapably exposed to this radiation. Our
ancestors have been exposed to it. The human race has evolved in such a
radioactive environment. Moreover, the biological effects from different
kinds of radiation can be compared in a meaningful way in terms of
roentgens. Therefore the danger from Sr⁹⁰ is not unknown in every
respect. In some ways it is very well-known because we and all living
beings have spent our days in a similarly dangerous surrounding. We live
on an earth which has radioactivity in its rocks, which carries a
similar activity in its waters, and which is exposed from all sides, to
a rain of particles which produce effects identical with the effects of
radioactive materials.
Not all radiations which have the same intensity (the same number of
roentgens) have precisely the same effect. The damage produced also
depends somewhat on the spacing of the ionized and disrupted molecules.
The cosmic rays and the Sr⁹⁰, however, are quite similar even in this
respect.
The reader will recall that the spacing of the ionization depends only
on the charge and the speed of the ionizing particle. The ionizing
particle from the Sr⁹⁰ is an energetic beta ray, which has a charge of
one and a speed close to that of light. A large part of the background
radiation which reaches our bones comes from the cosmic rays. The main
portion of the cosmic rays is due to the mesons. The meson, like the
beta ray, has a unit charge and a speed close to that of light. The two
particles may therefore be expected to produce identical biological
effects. The only difference between their effects is that the beta ray
does not have enough energy to leave the bones, while the meson is so
energetic that it deposits its energy both in our bones and throughout
our whole body. Thus if we compare a Sr⁹⁰ dose with the same dose of
cosmic rays the same effect to the bones must be expected. But the
cosmic rays give rise to additional effects in our bodies.
The total background dose to the bones is about 0.15 roentgens per year
for the average person living at sea level in the United States. Of this
amount, about 0.035 roentgens is due to cosmic rays. At higher altitudes
the cosmic ray dosage increases. In Denver, at an altitude of 5000 feet,
the cosmic rays contribute 0.05 roentgens per year.
The above numbers should be compared with the present level of
world-wide fallout radiation to the bones: about 0.003 roentgens per
year (from Sr⁹⁰ and other sources). The fallout radiation is thus only a
few per cent of the natural cosmic radiation. It is small even when
compared to the variation of cosmic ray intensity between sea level and
5000 feet.
A correlation between the frequency of leukemia and bone cancer, and the
intensity of natural radiation has been looked for. Some statistics for
the year 1947, before weapons testing began, are available. They show
the number of cases of these diseases occurring in that year per 100,000
population.
_Bone Cancer_ _Leukemia_
Denver 2.4 6.4
New Orleans 2.8 6.9
San Francisco 2.9 10.3
The extra radiation that one gets in Denver from cosmic rays is many
times greater than the fallout radiation. But the table shows no
increased incidence of bone cancer or leukemia. On the contrary—the
incidence of these diseases is actually lower in Denver.
Not all of the natural background radiation is due to cosmic rays. Part
of the background comes from natural radioactive elements in the soil
and in the drinking water. These include uranium, potassium⁴⁰, thorium
and radium. Radium behaves like calcium and strontium, and gets
deposited in our bones. All these effects are, to the best of our
knowledge, at least as intensive in the Denver area as in San Francisco
or New Orleans.
One possible explanation for the lower incidence of bone cancer and
leukemia in Denver is that disruptive processes like radiation are not
necessarily harmful in small enough doses. Cell deterioration and
regrowth go on all the time in living creatures. A slight acceleration
of these processes could conceivably be beneficial to the organism. One
should not forget that while radiation can cause cancer, it has been
used in massive doses to retard and sometimes even to cure cancer. The
reason is that some cancer cells are more strongly damaged by radiation
than the normal cells.
In spite of the table, however, there may actually be an increased
tendency toward bone cancer and leukemia that results from living in
Denver. If so—and this is the main point—the effect is too small to be
noticed compared to other effects. We must remember that Denver differs
from New Orleans and San Francisco in many ways (besides altitude), and
these differences may also influence the statistics.
A more thorough consideration of the background radiation gives further
evidence that this radiation is more important than the present or
expected effects of Sr⁹⁰. The radium deposited in our bones from
drinking water has been observed to reach values as high as 0.55
roentgens per year. Furthermore the heavier and slower alpha particles
emitted by radium cause ionization processes which occur in closer
spacing and are therefore more damaging than the ionization due to Sr⁹⁰.
To make things worse radium is deposited in our bones in little nodules
(hot spots). Thus the possibility of local damage is enhanced.
The background radiation to which we are exposed varies for some
unexpected reasons. It has been pointed out recently that brick may
contain more natural radioactivity than wood. The difference between
living in a brick house and living in a wood house could give rise to
ten times as much radiation as we are currently getting from fallout.
(The additional radiation from the brick might be as much as 0.03
roentgens per year.)
Human beings are subject to radiation not only from natural sources, but
also from man-made sources. One of these is wearing a wrist watch with a
luminous dial. Another is having X-rays for medical purposes. Both of
these sources give much more radiation than the fallout.
Of all ionizing radiation to which we are exposed the X-rays are most
important. In some cases medical X-rays have intensities which are
noticeably harmful. Yet this damage is practically always of little
consequence compared to the advantage from correct recognition of any
trouble that the X-ray discloses.
We may summarize in this way. Our knowledge of the effects from the
fallout is deficient. We cannot say exactly how many lives may be
impaired or shortened. On the other hand, our knowledge is sufficient to
state that the fallout effect is below the statistically observable
limit. It is also considerably less than the effect produced by moving
from sea level to an elevated location like Denver, where cosmic
radiation has a greater intensity. It is also less than having a chest
X-ray every year. In other words, we know enough to state positively
that the danger from the world-wide fallout is less than many other
radiation effects which have not worried people and do not worry them
now.
We have compared radiation from the fallout with radiation from other
sources. It is also possible and helpful to compare the fallout danger
with different kinds of dangers. For this purpose it is convenient to
express all dangers in terms of a reduced life-expectancy. For example,
smoking one pack of cigarettes a day seems to cut one’s life-expectancy
by about 9 years. This is equivalent to 15 minutes per cigarette. That
cigarettes are this harmful is, of course, not known with certainty. It
is a “best guess,” due to Dr. Hardin Jones, based on an analysis of
statistical data. A number of Dr. Jones’ statistical findings are listed
in the following table:[13]
_Reduced
Life
Expectancy_
Being 10 per cent overweight 1.5 years
Smoking one pack of cigarettes a day 9 years
Living in the city instead of the country 5 years
Remaining unmarried 5 years
Having a sedentary job instead of one involving exercise 5 years
Being of the male sex 3 years
Automobile accidents 1 year
One roentgen of radiation 5 to 10 days
The world-wide fallout (lifetime dose at present level) 1 to 2 days
The reader will see that the world-wide fallout is as dangerous as being
an ounce overweight or smoking one cigarette every two months.
[Illustration: How people get radiation
Average dose in roentgens per year]
The objection may be raised that the fallout, while not yet dangerous,
may become so as more nations develop and test atomic weapons. On this
point we can only say that the future is not easy to predict. Some
factors, however, justify optimism. We are learning how to regulate the
fallout by exploding bombs under proper surroundings. Development of
clean bombs will greatly reduce the radioactivity produced. Deep
underground tests will eliminate fallout altogether. The activity put
into the atmosphere in 1954 was considerably greater than the activity
released in any other year. It is highly probable that the activity
produced by United States tests will continue to decline.
Finally, we may remark that radiation is unspecific in its effects.
Chemicals are specific. About the effects of a new ingredient in our
diet, in our medicine, or in the air we breathe, we know much less than
we know about radiation. If we should worry about our ignorance
concerning our chemical surroundings as we worry about the possible
effects of radiation, we would be condemned to a conservatism that would
stop all change and stifle all progress. Such conservatism would be more
immobile than the empire of the Pharaohs.
It has been claimed that it is wrong to endanger any human life. Is it
not more realistic and in fact more in keeping with the ideals of
humanitarianism to strive toward a better life for all mankind?