missile bases in the American heartland, the controversy over
the testing of nuclear weapons--these are immediate examples.
In spite of their import for our future, the decisions of govern-
ments on these matters are not being formed and guided by
public opinion. Apparently the difficult and subtle nature of
nuclear problems turns most laymen away, and the distortions
of public discussion have left those who have tried to under-
stand in confusion and despair.

This book is an attempt to give a clearer picture of these
nuclear problems. We have attempted to present simply and
authoritatively the facts about nuclear weapons and the threats
they raise to mankind. We have taken the hazard of radioactive
fallout as our main theme. There are three reasons for focusing
on this aspect of the nuclear danger. First, the public debate of
the weapons testing issue has centered on the fallout hazard, and
much confusion has resulted from the incomplete and contra-
dictory arguments presented. Secondly, intensive scientific stud-
ies in the last three or four years have produced a wealth of
factual material which should be transmitted to the public.
Third, any estimates of the biological effects of a nuclear war
are in the last analysis largely drawn from present studies of the
fallout from bomb tests.

The magnitude of this fallout hazard has been the main sub-
ject of political and scientific debate, and we shall examine the
principal elements of the controversy in later chapters. It is well
to start, however, by realizing just what is in dispute and what
is not.

The explosion of a nuclear weapon produces radioactive debris
which is carried on the winds to all parts of the world; it falls
with the rain and enters the food cycles of plants and animals.
That there has been a steady increase of radioactivity in our soil
is not questioned; it can be and has been clearly demonstrated
in many experiments, well exemplified by one performed by
soil scientists at Earlham College in Indiana. In 1950, as part
of a long-range study, a sample of topsoil was carefully set aside.
In mid-1959 a second sample was taken from the same place.

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