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56
concentration which can occur from the domestic chimney, especially
during periods of inversion. Another important point is that the domestic
smoke is concentrated more in the winter months, being especially heavy
during cold weather or during times of fog, predominating then at times
when the smoke concentration is most dangerous. It is, of course, true that
today's efforts are to reduce the content of smoke. Even were the position
that nothing was being done to reduce the concentration of the harmful
oxides of sulphur, any reduction of smoke content would still be helpful
because sulphur dioxide is more harmful when associated with smoke
than when emitted alone. But the position of course, is that the acceptance
of smoke control areas results in more efficient thermal units being used,
and so causes a diminution in the amount of fuel burned which, in turn.
reduces the amount of sulphur gases. The coal open fire has a very low
thermal efficiency which results not only in its creating the worst forms of
smoke, but, because of the amount of fuel used, results in more sulphur
gases being emitted.
Hazards of Radiation
In June, 1956 the Report of a Special Committee of the Medical
Research Council on the Hazards to Man of Nuclear and Allied Radiations
was presented to Parliament. This report set out the then position
about the risks. It referred to the natural radiation to which mankind is
exposed from certain radioactive elements in the earth and from cosmic
radiations, and also to the exposure which man himself has added,
namely, that derived from the use of various forms of radiation in
medicine and industry, and from radioactive isotopes of chemical elements
which are produced in nuclear reactors and high energy machines, or
from the explosion of nuclear weapons. The Committee pointed to the
many large gaps in knowledge of the medical and biological effects of
ionising radiation, and recommended that much research on many fronts
should be undertaken. A second report of this Committee was presented
to Parliament in December, I960. In preparing this the Committee had
the benefit of much new information on the measurement of radiation
and on permissible levels. The facilities available for measuring the
constituents of fall-out in air, water, food, herbage and other materials
had been greatly extended.
On the concept of a threshold dose of radiation the report says—
"In considering the possible practical effects on man of exposure to
radiation, we therefore think it prudent to continue to assume that even
the lowest doses of radiation may involve a finite, though correspondingly
low, probability of adverse effect."
In regard to the effect in causing leukaemia, the Committee says—
"We have carefully considered the suggestion that local variations in
fall-out may have influenced the incidence of leukaemia in particular
districts ; but in fact the local death rates from leukaemia are not consistently
related to the figures for fall-out and taking all the evidence into
account we think they cannot be related to this factor.