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of it in relatively fresh fission products, it is the chief concern when fission
products are rapidly deposited on agricultural land as, for example, after
a reactor accident. Being volatile, it is particularly likely to escape in many
types of accident. Milk will be the most contaminated food if the accident
occurs when dairy cattle are grazing in open pastures because cows derive
their food from wide areas of grass and iodine is rapidly transferred to
milk. Iodine 131 is however, very easily detected even in doses small
enough not to be dangerous, and the time elapsing between the deposition
of iodine 131 on grass and its appearance in high quantity in milk, is
enough to allow emergency plans to be put into operation.
The isotopes of strontium are less abundant than those of iodine in
fresh fission products, but they are much more persistent. The half life of
strontium 90 is twenty-eight years; with the passage of time then it
becomes the chief cause of concern. It is for this reason that the effects of
fall-out from nuclear weapons have been largely concerned with strontium
90; the short-lived iodine has largely disappeared before the fall-out
reaches the earth's surface. The extent to which strontium 90 enters diet is
examined on an extensive scale in the United Kingdom as well as in other
countries, special attention being given to milk which contains half the
total strontium 90 in Western diets. Special studies are also made in areas
where local conditions cause the quantity of strontium 90 in diet to be
above average. The results published at intervals by the Agricultural
Research Council show that they are everywhere below that judged safe
on medical grounds. Strontium 90 in diet largely consists of the recently
deposited fall-out trapped directly on plants. With few weapon trials, the
rate of fall-out is decreasing.
Radioactivity can enter human food by means other than by the
contamination of agricultural land. Diluted radioactive effluent may be
discharged into rivers or into the sea from nuclear plants, and so enter
fish or marine plants. These releases can be strictly supervised and controlled.
New sensitive detection procedures now make it possible to measure
the small quantities of naturally occurring radioactive substances that
have always been present in human diet. In total this natural radioactivity
greatly exceeds the artificially produced radioactive substances that are now
present in food.
(E) HYGIENE OF FOOD
Some ten years ago, the Council embarked on a food hygiene campaign.
With the removal of the shortcomings at those premises which did not
reach desirable standards and later with the introduction of the Food
Hygiene Regulations which gave the force of law to those standards which,
up to then, had been reached by agreement, the conditions improved