View report page

21
be no association either direct or indirect, the apparent relationship being
purely coincidental. Of the enquiries in this country on the relationship
of smoking and the incidence of cancer of the lung, perhaps the best
known is that of Professor Bradford Hill and Dr. Doll based on the
information of the smoking habits of members of the medical profession
and correlated with the findings of the causes of their deaths. This enquiry
showed that there was a higher mortality in smokers than in non-smokers,
a higher mortality in heavy smokers than in light smokers, a higher
mortality in cigarette smokers than in pipe smokers and a higher mortality
in those who continued to smoke than in those who gave it up. When
the findings are broken down to the degree that they are in this report and
still retain their correlation, they can point only to smoking being a
factor. As the report of the Medical Research Council in 1957 says "In
the opinion of the Council, the most reasonable interpretation of this
evidence is that the relationship is one of direct cause and effect."
There are those who will not accept this conclusion. They point out
on the one hand that many, even the great majority, of heavy smokers,
reach an advanced age without developing this complaint and on the other,
that non-smokers have suffered from it; that investigations have not
shown any increased incidence amongst smokers who inhale as compared
with those who do not, and that in spite of the increase in cigarette
consumption by women the incidence of lung cancer in them is very low.
In regard to the point about only a small proportion even of heavy
smokers suffering, the explanation could be the general question of
predisposition. In those non-smokers who contract the infection the
triggering presumably was by some other carcinogen, possibly something
in the polluted atmosphere. That those who inhale are not greater
sufferers than those who do not, is indeed a weakness in the case incriminating
the cigarette as it can only be presumed that if cigarette
smoking is the direct cause, any carcinogens are that much more liable to
start the trouble in those who inhale than in the other group. Today's
relative freedom of women from the complaint, in spite of their growing
practice of smoking, is not a point against the conclusion; it can only be
feared that when enough women have smoked heavily enough for long
enough, when they have reached the years of susceptible age range, they
too will suffer heavily.
There are those who claim that the attention being focussed on the
subject is merely a fad of the statisticians—that whatever the figures may
Point to, there is no proof that cigarette smoking is in fact really the cause
of the trouble. Such actual proof is, of course, virtually impossible to
obtain. It is accepted that there are at least five chemical substances in
tobacco smoke known to be capable of causing cancer in animals. It is
known too that the local application of tobacco tar to the skin of mice
can cause cancer.
As to what might be the damaging factor, opinions vary. Some
suggest that the paper of the cigarette is of importance, and that it is this
that accounts for the higher incidence in those smoking cigarettes than
pipes. Others see the actual temperature as a factor of importance, while
other again would incriminate the tar condensate. Either of these latter
two factors might be felt to account for the relatively higher incidence of