SELL
the International Commission on
) mind in this context, but diffi‘onmental situations. This is not
of ICRP were directed primarily
RADIOACTIVITY IN AGRICULTURAL PRODUCTS
5
criteria is whether the limits of dose recommended by ICRP for members
of the population living in the neighbourhood of controlled areas (i.e. Group
B (c)) are to be regarded as applicable to each separate individualor to the
average for small groups living under comparable conditions. ICRP gives
m the exposure of the population
one the less, the general intentions
illy from the addendum to its
ing to the exposure of the popu-
no specific ruling on this question but it may be considered to point the way
to a sensible interpretation. It does not use the words “for any individual”
in specifying limits of dose for Group B (c) though they are applied to the
: exposure of the population
tion is the dose received by
xt the MPC values or other
Commission did not specifically recommend that its criteria should be
ed.”
ded as applying also to persons
reas (i.e. Group B (c) ), andit is
oncerned. This principle has a
1¢ nuclide is determined by the
levels in individual components
o far as they contribute to this
ake of different nuclides differs
1a, beta or gammaactivity have
nsidered.
dose, and not the radioactivity
ficance of dietary contamination
: Nuclides and foodstuffs which
| a few nuclides will always be
tea and that they will enter the
be confined to these “critical”
can conveniently be applied to
the phrase “critical organ”. As
1 of food chain studies to the
he unequivocal identification of
stances.
tion of environmental contami-
are concerned are defined by
nany authorities agree that the
le year need not be considered.
lating to the basis of protection
. 10.
other special groups B (a) and B (b) (ICRP Recommendations’, compare
paras. 54 and 55). While it may be debated whether this small contrast in
the usage of words was intentional or not, it must be concluded that the
applied separately to single individuals in Group B (c). Commonsense, the
ultimate arbiter, points to the same conclusion. In the well chosen words of
the White Paper on the control of radioactive waste”:
“Tt is impossible to examine the habits of every individual. The
normal procedure is to investigate the habits of a sample of the
population involved. ... There must always remain the possibility
that somebody of such grossly different habits as to be unpredictable from the observed pattern in the sample may receive
exposure higher than a tenth of the occupational maximum
permissible level. However, since safety factors are generally
retained in these estimates, the possibility is remote. In our view
this approach is satisfactory.”
The words “safety factor” are the key to the situation, though it might
be argued that the words “the smallness of any risk to the individual”
might have been as appropriate. ICRP have stated that any effects caused
by exposure to the maximum permissible occupational level (that is to say,
10 times that set for Group B (c)) would be so small that they could be
detected only by statistical methods applied to large groups (ICRP Recommendations”, para. 31) and although accurate quantitative estimates of the
risks associated with exposure at these low levels of radiation cannot be
made, it is apparent that they are very small relative to the many hazards
of everyday living against which the community takes no measures.
One obvious and unavoidable difficulty arises from the conclusion that
we are concerned with the mean exposure of a small group, not individuals.
The small group cannot be specified in rigid terms. The manner in which
it is defined can only be decided in the light of local circumstances. There
is, however, one aspect on which we can be specific, namely, that different
age groups should be considered separately. In practice the risk to young
children will usually be dominant, not only because they may be more
sensitive to radiation injury but because frequently, as will be shown later,
environmental contamination is likely to expose them to the highest doses.