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Environmental radioactivity
Experimental studies were continued with the object of obtaining reference data on
environmental levels of ionizing radiation and to determine the extent of any contamination
which might arise through the widespread applications of nuclear science. Such contamination
could result from reactor accidents in this or neighbouring countries and more locally
from unguarded use of radio.isotopes or careless disposal of wastes, quite apart from
fallout from nuclear weapons.
Continuous monitoring of the atmosphere was again maintained and no significant
additions of radioactivity or other disturbing features were observed during the year.
Compared with previous years, there was a marked reduction in the amount of radioactive
matter reaching the lower atmosphere from the residue of old fission products still suspended
in the stratosphere.
A national survey undertaken by the Agricultural Research Council has provided figures
for the amount of strontium.90 which occurs in human diet. The determinations have been
made on particular classes of food such as meat, vegetables, cereals, milk and its products,
etc.; by making allowance for losses in preparation, and the average quantities used in
diet, an estimate can be made of the amount consumed. It was thought that the alternative
approach of making direct determinations on complete meals would be of value and a
limited investigation on these lines was undertaken in the L.C.C. laboratories during the
year. The samples examined were complete two.course midday meals taken at random
from those being served to L.C.C. schoolchildren. Meals from three different kitchens
were bulked for the analysis. The figures applying to samples taken in 1960 were lower than
those calculated from national data for the preceding two years; this difference probably
reflected the decreased deposition of strontium.90 during 1960, and also the fact that the
strontium content of foods available in the London area tends to be lower than the national
average.
Another direct responsibility of the Council is that of ensuring safe conditions in sewers
receiving radioactive discharges. Hospitals are at present the largest users of such disposable
matter in the London area, although there is growing use in industrial and research
laboratories. Investigations on these aspects were undertaken.
Swimming baths and ponds
The Council has under its control 13 swimming baths and three bathing ponds for
public use and 30 baths situated at schools and institutions: of these 24 are sited outdoors
and 22 indoors. It is the Council's policy to equip all the baths with complete purification
plants and during the past year three further complete purification plants were installed,
bringing the total to 33. Two of the new installations have diatomaceous earth filtration,
installed by parent.teacher associations and taken over by the Council for running and
maintenance. Three more baths have plant for gas chlorination and circulation only and
seven are chemically treated by hand.
The Scientific Branch collaborates with the staff of the Chief Engineer, the Chief Officer
of the Parks department and other interested departments to ensure efficient water treatment.
A careful check is kept on the condition of the water by means of daily tests by the
bath attendants. These results are embodied in weekly returns made to the branch. Visits
by officers of the branch to each bath are made at four.weekly intervals for inspection,
testing and sampling. During 1960, 348 samples of water were examined chemically,
690 bacteriologically and 984 chlorine and clarity tests were made.
As an example of the efficiency of treatment the figures obtained from 13 fully equipped
public baths during the five months summer season may be quoted. These baths are filled
with water from the Metropolitan Water Board mains and are emptied and refilled only
once a year. The weather during the summer of 1960 was not as good as the previous
year and consequently the baths were not so heavily used. During this period about 800,000
people used the baths compared with a figure of 1,750,000 during 1959. The minimum
recorded clarity was 10 feet, whilst the maximum was 150 feet.
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