(Reprinted from Nature, Vol. 209, No. 5028, pp. 1062-1065,
March 12, 1966)
PREDICTION OF FUTURE LEVELS OF
LONG-LIVED FISSION PRODUCTS
IN MILK
By B. O, BARTLETT and Dra. R. SCOTT RUSSELL
Agricultural Research Council Radioblological Laboratory,
Wantage, Berkshire
INCE
1958, when the
United
Nations
Scientific
Committee on the Effecte of Atomic Radiation! made
its first comprehensive review of the consequences of
world-wide fall-out, many attempts have been made to
derive formulae for calculating the level of radioactivity
in foodstuffs which is likely to be caused by different
patterns of environmental contamination. Information
has been obtained mainly by analysing relationships
between measurementsof fall-out and of dietary contamination made in environmental surveys. Controlled experi-
ments on food-chain mechanisms and information on
agricultural practices are, however, important supplementary sources of guidance; besides indicating whether
relationships suggested by survey results are causal or
fortuitous they can reveal factors which, though unimpor-
tant under conditions so far experienced, may require
greater consideration in the future. Improved information
can be expected as the period during which observations
have been made becomes longer because both climatic
factors and variations in the seasonal distribution of
fall-out influence the transfer of radioactivity to diet.
Conclusions previously reached in the United Kingdom?-*
have, therefore, been reviewed in the light of the more
extensive data which are now available.
Consideration has been limited
to
two nuclides,
strontium-90 and caesium-137, in a single foodstuff,
milk. These two nuclides are mainly responsible for the
internal radiation doses to which long-lived fission
products give rise and it is well established that the
contamination in milk has provided a good guide not
only to the exposure of children but also to that of adults
who consume a mixed diet of the type normal in Western
countries’. Moreover, the data on the contamination of
milk are considerably fuller and more reliable than those
for other foodstuffs.
:
The annual average levels of contamination in milk
throughout the United Kingdom have alone been con-
sidered; predictions for smaller areas or shorter periods
would be subject to much greater uncertainty.
The
country-wide average deposition of strontium-90 used
in the present calculations has been derived, from the