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Some are used for radio-therapy, e.g. radium, cobalt 60, caesium 137,
gold 198, iodine 131, phosphorus 32. One of the risks these substances
give rise to is that from exposure. In hospitals, regulations lay down the
arrangements about storage, the use and movement of the materials and
the disposal of waste. A second risk is in regard to the disposal of waste
from wherever these materials are used. These special problems are
covered by the Radio-active Substances Act, 1948.
Nuclear Reactors. In ordinary circumstances the operations at
the nuclear reactors which are covered by the Atomic Energy Acts, are
no risk. There are risks though both to those working at the reactors
and those living in the neighbourhood, when an accident such as that of
Windscale on the 10th October, 1957 occurs. There is too the ever present
problem of disposing of large quantities of radio-active waste. The
methods include storage, disposal on ocean beds, and land burial. All—
whether solid, liquid or gas—call for rigid control of their transport and
of their final resting place.
A great hazard from the release of radioactivity into the air is
contamination of human food. This may be by the short chain (air, plants,
grazing animals, milk and man) or the long chain. There are two fission
products above all others which are a special hazard : iodine and
strontium, the one accumulating in the thyroid, the other in bones.
Iodine with its shorter half-life and its being in greater amounts is the
greater risk shortly after the release. The contaminated grass is consumed
by cows and radioactive iodine appears in the milk. This risk led to the
decision to destroy much of the milk produced near the Windscale plant
following the accident there. The transfer of iodine from diet to milk is
very rapid. The hazard is much less if the milk is used for making butter
or cheese or other manufacture. The next most serious risk is leaf
vegetables; but this is small compared with that of milk. Strontium 90
with its longer half-life of twenty years becomes a factor of importance
later by its being absorbed by the soil, passing to plants, grazing animals
and human beings. It finds its way to bones where it is an internal source
of radiation. Examination of the bones of sheep in some localities has
shown an increase in the proportion of strontium. Fears have been
expressed at the presence of strontium in wheat grown in areas contaminated
by fall-out. Other foodstuffs which may be contaminated by
fission products include fish which can selectively accumulate certain
radio-nuclides in bones and tissues, watercress and sea-weed used to
make laver bread.
Another risk is of the radiation causing leukaemia. An enquiry about
a number of deaths from leukaemia in Heywood, Lancashire, led to an
official denial of there being any association of the increased number of
cases and the Winscale accident. The fall-out from Winscale was mostly
radio-iodine, whereas the agent causing leukaemia is strontium 90 which
occurs in test explosions.
Exposure of the gonads can result in mutations, the result of
in genes. Exposure might cause an immediate effect on the in
dividual, or the remote and possibly more marked effect on successive
generations. Any radiation dose however small, can cause mutaion.